Invertebrates of the Peloncillo Region: Richness and Mystery
Although few formal studies on invertebrate diversity have been conducted within the bounds of the Pelconcillo region, several sources of information suggest that this area represents one of the most diverse arthropod communities in the nation. Several factors contribute to this extraordinary richness, starting with the area’s tremendous plant diversity. The area’s location at the convergence of so many distinct biotic provinces undoubtedly also boosts diversity.
The area also shows many examples of species at or near the edges of their ranges. Here, for example, many predominantly tropical species can be found interacting with a suite of neighbors from all quarters of the continent. There are numerous known endemics (known only from parts of the Peloncillo region), and certainly more that remain undiscovered. Several are part of local radiations, with different forms on each nearby mountain range.
In addition to being species-rich, the invertebrate fauna in and around the Peloncillo Mountains is unusually interesting. The biology of this fauna is arguably better-known than in any comparably rich North American region. Virtually all animal behavior and ecology textbooks in the nation feature case studies discovered or developed in this region (many in the bajadas of the San Simon valley and the neighboring Chiricahua Mountains).
Outstanding Features:
Much remains to be discovered. Many fascinating species are known to occur in nearby lands, but researchers have not yet looked for them in this focal area. When they do collect in the Peloncillo region, researchers often find that their catches extend a species’ known range by hundreds of miles, add a new name to lists for the state or for the nation, or reveal a species entirely new to science. Even for species known to occur here, additional research often reveals that local populations have diverged from their outside relatives in genetics, morphology, and/or behavior.
Unlike the field of botany, in which researching the flora of specific sites still has prestige and is readily published, there is very little emphasis on place-based research in invertebrates. Information on what species live where exists, but is widely scattered and embedded in the small print of taxonomic monographs, ecological studies, and the like. Efforts to database entomological collections is making this information much easier to come by, but most collections are still in the early stages of this process.
Geographic scope. In desciption of the invertebrates of the Peloncillo region, most questions discussed here are applied to an area from the northern Peloncillo Mountain Wilderness south to Guadalupe Canyon and the border with Mexico, and from just east of the Animas Mountains across the Peloncillo Mountains to the San Bernardino and San Simon Valleys. Contiguous with the southern Peloncillos and Animas Mountains in Mexico lies the Sierra San Luis. The Sierra San Luis range has received very little attention by entomologists, but what has been discovered is quite spectacular; discussions here include this range when possible. Some data discussed in this report come from the Chiricahua Mountains just west of the San Simon Valley and/or from the grasslands of the Jornada Experimental Range some 50 miles east of the Peloncillo Mountains proper. Although these sites are interesting in their own rights, their data are used here only to fill in gaps in knowledge of the fauna in the area outlined in the previous paragraph.
Current Knowledge
Invertebrate species represent over 90% of the terrestrial species on the planet. Because of the sheer number of species involved, details of invertebrate diversity are notoriously difficult to document and to make sense of. The number of species reported from an area, for example, usually has more to do with how much attention the area has received than with how many species actually live in that area. This means, however, that each new effort brings many discoveries. It is not unusual for several of the species collected in a given sample to represent range extensions of hundreds of miles, or for a casual observation to reveal behavior or natural history never before known to science.
A report such as this addresses several types of questions and conveys various kinds of knowledge. First is the question of how many invertebrate species reside in the region. Next, what are these species? Where else do they live? What do they do in their own lives? How do they interact with each other, with other flora and fauna, and with abiotic factors such as soils and climate? How do management decisions affect them, and how do they affect outcomes of human activities? To the extent that our knowledge bears upon each of these questions, they are answered below under themes of species richness, species identities, distributions, biology and behavior, ecology, and management.
Sources of information within the region: The Peloncillo Mountains have received very little formal invertebrate research of any sort. More has been done in the San Simon Valley, some in and around the San Bernardino National Wildlife Refuge, and some in the Animas Valley. Most site-specific information that does exist for invertebrates in this area remains unpublished and has not been previously compiled in any accessible way. Other data remain to be compiled.
Much of our knowledge about invertebrates in this focal area therefore comes from personal communications with experts who have collected there. Sources of information extrapolated from nearby sites: Much of our knowledge about invertebrates in the Peloncillo region therefore comes from extrapolations, estimates, personal communications with experts who have worked with particular taxa, and studies done nearby.
Studies conducted just outside the region provide quite a bit of information about species that most likely also exist here, and about the ecological roles of invertebrates in similar habitats. Two main sources contribute the lion’s share of information: the American Museum of Natural History’s Southwestern Research Station (SWRS) and the Jornada Experimental Range (JER). Many of the scientists consulted on site-spec ific data have also worked out of one or both of these institutions.
The Southwestern Research Station is located on the east flank of Arizona’s Chiricahua Mountains, just seven miles across the San Simon Valley from the Peloncillo Mountains. SWRS has been one of the nation’s most productive sites for invertebrate research since 1955 when the station was founded at the urging of scientists who felt they had found entomological heaven. SWRS-affiliated scientists work throughout the Chiricahua Mountains, from mid-elevation pine- oak habitats that are well-represented in the Peloncillos, to higher mixed-conifer habitats that do not exist in the Peloncillos proper but do occur at the tops of the Animas and Sierra San Luis. They also work in the bajadas and bottomlands of the San Simon Valley, within the Peloncillo focal area.
Studies based at SWRS have spawned over 400 scientific research papers on insects, including over 200 on ants alone, plus some 60 papers on spiders and scorpions.5 This number does not include countless taxonomic papers that make use of specimens collected in this area, but are not primarily focused on this site. Unfortunately, taxonomic lists have been compiled for only a handful of the invertebrate groups studied in and around the Chiricahuas; most of the lists that do exist remain unpublished, available only from the list authors or informally circulated online.6 Nevertheless, the Chiricahua-based research is full of fascinating biological stories, and a determined researcher can glean from this scattered literature a large number of taxa that may well occur in the Peloncillos, as well as an idea of what these creatures may be doing. When a species is found in the Peloncillos, Chiricahua research can add depth to the discovery by bringing to bear previous studies on its behavior, ecology, and/or natural history.
The Jornada Experimental Range lies some 150 miles northeast of the Peloncillos in southern New Mexico. This experimental range was designated in 1912 when a Presidential Executive Order deeded 193,000 acres (78,000 ha.) of grasslands and Chihuahuan desert scrub to the U.S. Department of Agriculture, to be used for research on management and remediation of desert grasslands. The site was included in the National Science Foundation’s Long -Term Ecological Research network in 1982, which brought a renewed focus on understanding effects of climate change and other long-term processes on flora, fauna, hydrology, and soils. JER studies on invertebrates have focused largely on the roles of invertebrates in ecological dynamics such as herbivory and plant competition, nutrient cycling, and soil aeration and fertility. JER studies have also included species inventory work for particular invertebrate groups, and behavior and natural history of selected species.
Other sources of information by extrapolation: Because of the sheer magnitude of species involved, knowledge about invertebrate richness is generally dealt with differently than that of vertebrate taxa like birds, herps, or mammals. Extrapolations are based on rules-of-thumb relationships and sometimes just hunches. For other species, it is often assumed that lists of observed species are close to complete; i.e., that they represent the whole fauna present. In contrast, most invertebrate diversity discussions revolve around predictions and estimates; not even the best-studied parks in the nation claim to have a complete inventory of their invertebrate faunas. These predictions are ball-park endeavors. They may be based on correlation between taxa (e.g., between numbers of plant species and numbers of insects, or between, say, butterflies and beetles), or they may be based on equations that use the number of species that have been found only once or twice to predict how many have not yet been found at all. Many predictions do not include taxa such as mites or nematodes that are hyper-diverse but difficult to sample and identify well. The smaller the group, the more accurate estimates tend to be–e.g., predictions of butterfly diversity will be more accurate than predictions of insect diversity, and insect predictions will be more accurate than those of invertebrates as a whole.
Overall Patterns of Invertebrate Diversity
An overview of current understandings: Some of the area’s broader patterns are evident already, even with the limited amount of work done here. Several sources of information suggest that the Peloncillo region represents one of the most diverse arthropod communities in the nation. The area’s exceptional plant diversity (see Chapter 2.2) almost certainly drives much of the diversity of herbivorous insects such as butterflies, grasshoppers, and many beetles. As in other animal and plant groups, this area is a mixing ground for the temperate and tropical groups. Many groups range no farther north than this region, and others range no farther south. The region includes, for many taxa, representatives of species typical of the western reaches of the continent as well as species typical of the eastern reaches. There are some local endemics (especially in certain groups such as talus snails) and more for which this area makes up a large portion of their known range. The high elevations typically host very different invertebrate communities than do the low elevations. The diversity of soil types increases local diversity of many groups, and the high diversity of plant species brings with it a huge increase in insect diversity relative to other parts of the U.S. For a select set of taxa about which a noteworthy amount is known, information is summarized below and fleshed out later in the chapter. At the end of this chapter, we also outline preliminary strategies for improving knowledge of Peloncillo-area invertebrates.
Overall Species Richness
Intensive inventories could reveal an overall invertebrate diversity in the tens of thousands of species. The Great Smoky Mountains National Park has documented over 4,200 invertebrate species (mostly arthropods), and estimates that the total number may exceed 70,000. By virtue of its size and biogeographic location the Peloncillo region likely harbors at least as many as this park. Researchers making informal, conservative predictions of insect diversity in other southwestern parks estimate at least five insect species per plant species.8 This ratio predicts the Peloncillo region would harbor over 4,000 insect species alone, and that adding other arthropod groups such as spiders, scorpions, and centipedes would likely bring the total to well over 5,000 (not including hyper-diverse, difficult to survey taxa such as mites).9 This is probably a severe underestimate; in five years of collecting, one Smithsonian entomologist has found 4,000 insect species in his Maryland backyard. True arthropod diversity of the Peloncillo could be several times this number, given the huge diversity of hard-to-sample taxa such as mites and parasitoid wasps. Including other hard-to -sample non-arthropod taxa such as nematodes and other soil invertebrates would be the factor that brings the total diversity number into the range of the tens of thousands estimated at the Great Smokies park.
Insect collections done in the region support these richness predictions, as low end order-of- magnitude figures. The University of Arizona entomology collection already contains nearly 2,000 species from the neighboring Chiricahua Mountains; 1,009 of these are beetles. This collection represents mostly haphazard collecting rather than systematic attempts to inventory the range, suggesting that the additional collecting would add many, many more species.12 Richness of Hymenoptera, Diptera, and Lepidoptera could reasonably be expected to be on the same order of magnitude as that of Coleoptera. While many fewer collections have been done in the Peloncillo region,13 all but the highest-elevation Chiricahua species could occur here (and even these could occur in the taller Animas and Sierra San Luis Mountains).
Unusually High Diversity Within Groups
Bees take the grand prize for unusually high diversity, with over 400 species known from the San Bernardino National Wildlife Refuge alone and some 1,000 estimated to live within the Peloncillo region.14 This is far more than in a similar-sized plot of tropical rainforest. Ants and butterflies are close behind, with some estimated 200-300 species each. If beetles were better known for the area, they would likely rival or top each of these groups.
Biogeography: Regional Mixing Ground
The Peloncillo region represents an overlap and blending of several major biogeographic zones, spanning the transition from tropical to temperate and the saddle between the eastern and western slopes of North America’s mountain spine. Within this blending zone, the Peloncillo region hosts invertebrate species typical of the Chihuahuan Desert, Sonoran Desert, Rocky Mountains, Sierra Madre, and beyond. Butterflies exhibit some of the clearest examples of these patterns within the Peloncillo area. The Desert hoary-edge skipper (Achalarus casica), for example, is predominantly a Sonoran Desert species, while the range of the Chiricahua white (Neophasia terlootii) largely tracks that of the Sierra Madre. Similarly, the Eastern black swallowtail (Papilio polyxenes asterius) reaches its western -most U.S. distribution here, just where the Western orangetip (Anthocharis sara) nears its eastern edge. The Peloncillos lie at the south end of the ranges for some temperate and alpine species such as the Western tiger swallowtail (Papilio rutulus arizonensis) and the Western marble ( Euchloe hyantis). Many more species find their northern limits here. The Yellow brimstone (a.k.a. angled sulphur Anteos maerula), for example, ranges from here to Peru. The Black-tipped (a.k.a. yellow mimosa sulphur Eurema nise) ranges from here south to Argentina.
Endemism and Evolutionary Radiations
Of all the invertebrates examined here, mollusks have the highest known rates of endemism, with each mountain range in the region typically having at least one endemic species and most having more. Many of these are part of evolutionary radiations that are particular to the Sky Island region: species on various ranges have all diverged from a common ancestor, and each has become unique to its own small range. Talus snails of the genus Sonorella are well -known for this type of radiation in the Sky Islands. Several endemic Sonorella species occupy particular sections of the greater Peloncillo region.
One relatively well-known local radiation with a Peloncillo representative concerns the jumping spider Habronattus pugillus. This oak woodland spider has isolated populations on at least 18 Sky Island ranges. Each population is adorned with its own distinct set of courtship ornaments, and males on each range perform their population’s own unique dance for their females. The Peloncillos form, discovered in 1998, differs from all other population most strikingly in having shiny butterscotch-colored pedipalps, which males wave prominently during their courtship displays.
Edge-of-Range Representatives
The family Mutillidae (velvet ants) presents one of the clearest patterns of species near the edges of their ranges. The Peloncillo region includes several species such as Dasymutilla dugesii that reach their farthest south here, and even more that come from tropical ranges to their northern limits here. Dasymutilla magnifica and several more flow in from the western deserts to reach their farthest east here. Dasymutilla nigripes and others are mostly eastern species that “leak” across this low point of the Continental Divide.
Scorpions show some similar patterns, with Sonoran Desert species near the eastern edge of their ranges occupying many low elevation Peloncillos rock outcroppings. Chihuahuan Desert species more typical of lands east of here tend to occupy the valleys and bajadas.
Neotropical Representatives
Dragonflies are one of the best examples of Neotropical representation. Although several of the species known from this area are common throughout North America, and a handful of others are typical Western species, the majority are predominantly tropical. A number of our species range as far south as Brazil and Argentina. The Sky Island region of far southeastern Arizona and southwestern New Mexico forms most or all of the U.S. range for a dozen dragonfly species, and several more damselflies. These include the malachite darner (Coryphaeschna luteipennis ), the spotwinged meadowhawk (Sympetrum signiferum), and the plateau dragonlet (Erythrodyplax connata). The desert shadowdamsel ( Palaemnema domina) is the only representative of this tropical family to be found within the U.S.
While many, many tropical species in other invertebrate groups range as far north into the Peloncillo region, it is the tropical butterflies that attract thousands of humans each year to the Sky Islands to see species found virtually nowhere else in the U.S. Because of this attention, butterflies have become perhaps the best known of the invertebrates in the region. As one of the southernmost ranges with direct riparian connections into Mexico, the Peloncillos harbors more than its share of neotropical butterflies. Guadalupe Canyon in particular is a popular destination for many traveling butterfly fans.
Habitat Diversity
The Peloncillo region includes a wide range of habitat types. The diversity of tiger beetles is one of the best examples of how the diversity of habitats can boost that of species. Several of the region’s tiger beetles are specialists on alkaline salt flat habitats that periodically fill with water (known locally as playas ). Playa species include Cicindela willistoni, C. haemoragica, and C. nevadica. Grassland species tend to be restricted to grasslands; these include C. pulchra, C. horni, C. debilis, and C. obsoleta. The latter is so particular about its haunts that it is considered a possible habitat quality indicator for healthy native bunchgrass habitats. Another species, Amblycheila baroni (suspected but not yet confirmed in the region), lives only at the bases of large granite boulders.
Vulnerable Species and Habitats
Few invertebrates are officially listed as threatened or endangered, simply because we don’t have enough information about each to know which are vulnerable. Several of the Peloncillo region’s narrowly endemic talus snails and springsnails are officially considered species of concern. Some entomologists in the region also consider the unicorn mantis (Pseudovates arizonae) a species of concern due to its rarity and localized distribution21; this species has been found in the southern Peloncillos.
General landscape protections established for wide-ranging “umbrella species” such as jaguars or wolves will preserve habitats needed by most invertebrates. However, some species with very small ranges or very specific habitat requirements may need additional targeted management. Endemic talus snails or springsnails, for example, may live on just one hillside or in one isolated cienega. Negative impacts to such small areas can usually be avoided easily—if the need to do so is recognized. Invertebrate diversity can pop up in surprising places: rare soil types may harbor unique native bees; stabilized dunes may be home to tiger beetles found nowhere else in the region; rain may turn a shallow dry puddle into a seasonal pool teeming with fairy shrimps and other crustaceans. Plant assemblages such as willow thickets that form valuable parts of other animals’ habitats may be the only thing that sustains a species such as the increasingly rare viceroy butterfly.
The valleys and mountains of this region have a wide variety of ephemeral waters, including alkaline playas, stock ponds, seasonal washes, rock holes, and other puddle-forming sites. These pools fill with water for anywhere from a few days to several months, once a year or several times per year, and provide habitats for an untold number of invertebrates. Within weeks of a filling rain, pools such as these have been documented accumulating over 100 invertebrate species, many of which are found only in these habitats. When a pool dries, mobile species, including most of the aquatic insects, leave to find other waters or to complete a dry-land phase of their lifecycle. Others, including the freshwater crustaceans, stay put and enter a state of suspended animation until their own pool refills – perhaps many years in the future. Riparian areas also contribute disproportionately to the Peloncillo region’s total invertebrate diversity, even though they comprise a small percentage of its overall acreage. Native bee diversity tends to be highest in riparian areas, as does that of butterflies, beetles, ants, spiders, and more. Many of these invertebrates depend on the many plant species that grow only in more mesic parts of the focal area, while others depend on riparian areas’ increased abundance of potential prey species, on soft riparian soils, or on the availability of water itself. Springs provide some of the same general resources; they also provide isolated patches of habitat that tend to support a unique set of species, including some endemics.
The diversity of soils present in the region includes micro-habitats important to invertebrates such as ground-nesting bees and tiger beetles but overlooked by most humans. Experts strongly suspect that some patches of unusual soils contribute disproportionately to invertebrate diversity, but the identity and location of such soils are still subjects of speculation.
Additionally, many flying insect species engage in a behavior called “hilltopping,” in which males and females congregate at the tops of hills to find mates. These topographical “singles bars” may seem to humans as unremarkable bumps on the landscape, but development of hill tops (e.g., homesites) can interrupt the lifecycles of many dragonflies, butterflies, beetles, and other invertebrates.
Discussion by Invertebrate Group
MOLLUSKS
Most mollusks known from the region are land snails from several genera. Studies in the 1950s on land snails of central and north-central New Mexico found that lands between 8,100 and 10,000 feet in elevation tended to harbor the most species of land snails, with slightly fewer from 7,100 to 8,100 feet and many fewer below 7,000 feet. Not surprisingly, more mollusks are known from the Animas Mountains than from the Peloncillos. Local mollusk expert Richard Worthington lists 22 species from the Peloncillo and Animas Mountains. Little is known about the mollusk fauna of the Peloncillo region south of the Mexican border (Sierra San Luis). Because mollusks in the area remain poorly studied, any conclusions regarding diversity should be regarded as tentative pending further study. In particular, experts note that permanent water resources have not been adequately checked for mollusks.
Endemism: The most notable feature of mollusks in this region is how many are endemic to very small areas, often to just part of one mountain range. Across the Southwestern US, high - elevation land snails in these isolated mountain ranges tend to be restricted to one or two mountain ranges, and some are found only in one part of one range. Nearby ranges often harbor related but distinct species. Several snails now known from one small area have been found as Pleistocene fossils from other sites, suggesting that some of this endemism is relatively recent (e.g., within the last 13,000 years) and that these snails may be good indicators of climate change.
The Peloncillo Mountains have an endemic mollusk, the talus snail Sonorella hatchitana peloncillensis. The genus Sonorella is known for its high rates of endemism in the region. S. h. peloncillensis appears to be restricted to the Skull Canyon area of the range. Other par ts of the range with apparently suitable habitat have been studied but no other populations have been found. One Sonorella shell that may belong to this species was collected in Doubtful Canyon to the north. However, because the individual was immature and species-specific diagnostic features of adult genitalia are not present in immature shells, we cannot know for certain whether this shell represents a population of S. h. peloncillensis or not.
The Animas Mountains are home to three endemic snails, including the talus snail, Sonorella animasensis. This species is known from near Black Bill Spring, from the north slope of Animas Peak, and from Indian Creek Canyon. All were found in rock rubble and talus of steep slopes. The Animas Peak woodland snail (Ashmunella animasensis) is known only from volcanic rock talus slope in the high elevations of the Animas Mountains. Little else is known about this endemic snail. The Animas Mountains tube-shell (Holospira animasensis ) was described in 2003 from the base of a limestone cliff. The species is now considered to be endemic to the Animas Mountains, since live specimens have been found only in this single mountain range. Fossil shells of what appear to be the same species are known from the nearby Little Hatchet range, suggesting that these snails were more widely distributed during the last ice age.
The San Bernardino NWR harbors an endemic water snail, aptly named the San Bernardino springsnail (Pyrgulopsis bernardina; also referred to as Fontilicella sp.). This species lives solely in the small complex of springs and spring outflow waters of the SBNWR and adjacent lands. While management at the SBNWR is primarily directed at native fishes and frogs, water- related activities are evaluated and adjusted for the protection of this endemic snail.
Other mollusks from the region: Two aquatic species have been found in Clanton Canyon of the Peloncillo Mountains, including the ash gyro (Gyraulus parvus) and Physella virgata. Both are widespread in the U.S. Three other snails are known from the Blue Mountain region of the Peloncillos. The whitewashed rabdotus snail (Rabdotus durangoanus) is a cone-shaped land snail known only from New Mexico. The Southwestern fringed-snail (Thysanophora hornii ) is a desert snail characteristic of the low, arid mountains of the southern part of New Mexico and Arizona. T. hornii needs some cover, for which it will use leaf litter, dead sotol (Dasylirion ) or yucca stalks, or rock rubble and talus. The genus Thysanophora is Neotropical, reaching the northern edge of its range just north of here in Sierra County, New Mexico. A specimen closely resembling the Santa Rita ambersnail (Succinea grosvenori) is also known from Blue Mountain, but difficult taxonomy makes it unclear whether the specimen truly belongs this species or to a closely related species (Worthington pers. com.).
The shortneck snaggletooth snail (Gastrocopta dalliana dalliana) is known from Indian Creek Canyon in the Animas Mountains, as well as numerous localities in Arizona and Mexico. The species has also been reported from fossil deposits from Santa Rosa (Guadalupe County, New Mexico), where it was found in flood-related deposits along the Pecos River. Because it has only been collected once in New Mexico and its population trends overall are unknown, it was considered for endangered species listing in 1994. This consideration has since been dropped, but it remains a federal “species of concern.”
Special management concerns: The main threat to mollusks in this region is destruction and degradation of springs. Fortunately, the San Bernardino National Wildlife Refuge is working to protect the springs under their management, and staff are alert to the needs of the endemic snails. Talus slope endemics are probably much less vulnerable. Even though they, too, are known from very small areas, talus slopes don’t tend to be consumed and altered by humans in the way that springs are. Nevertheless, care should be taken not to alter these small patches of habitat. Neither prescribed burns nor fire suppression is likely to affect species on rocky slopes with little vegetation. Woodland snails, however, could be vulnerable to extreme fire events. (See Appendix G for a list of Peloncillo mollusks, compiled by Richard Worthington.)
INSECTS
Order Hymenoptera: Bees, Wasps, and Ants Bees
Extraordinary diversity: The most notable feature of this region’s bee fauna is its extraordinary species richness. More than 300 species of bees have been found in an area of about 12 km2 around the San Bernardino NWR (SBNWR) and adjacent Rancho San Bernardino (RSB). In the spring months, more than 100 species are active at the same time in the same place. When one considers the Peloncillo and Animas Mountains and their flanking Animas, San Simon, and San Bernardino valleys, bee diversity probably exceeds 1,000 species. Because the abundance of many native bee species varies tremendously from year to year, it may take several seasons of collecting to find most of the species that could be called “common,” and many more to develop a relatively complete species list.
Certain habitats contribute disproportionately to this diversity. Habitats where standing water is present support larger bee populations, probably because plants growing there bloom longer and are more abundant. Nesting habitats are also a limiting resource for many native bees. Though each bee species tends to have quite specific requirements for nesting, certain habitats are probably important for more than their share of species. Bees that nest above ground adopt beetle burrows in trees, so forested areas with mature trees (e.g., riparian forests and mesquite bosques) are likely to be especially valuable. Most bees nest in the soil, so areas with loose but stable soils, dunes, wash edges, and the like can be very attractive to bees.
The ecological roles of bees as pollinators mean their importance as a group exceeds that of just their numbers of species. Among the bee species in the Peloncillo area, about 40% are specialists that visit only one or several very closely related plant species. The degree of plant specificity presumably is one reason this area has the highest biodiversity of bees in the world.
The island effect: At least two species are restricted to mountaintops, with no apparent migration between populations. One (Lasioglossum boreale) has a northern distribution that is isolated on mountaintops in the southern edge of its range. The other species (Mexalictus californica) extends from the Sierra Madre Occidental north on Sky Isla nd mountaintops to the Santa Catalina Mountains near Tucson.
Edge of ranges: A number of species that are common farther south are known as singletons (only one specimen collected in a given place) in southeastern Arizona and northeastern Sonora.36 One example of this phenomenon is the capture of single specimen of orchid bee in Arizona. Not only is this the northernmost record for this species, the species itself is a northern representative of a solidly tropical tribe that contains some 180 species in the New World tropics. Minckley and Reyes note nine other predominantly tropical bee genera that reach their northernmost limits in the Madrean Sky Island region.
Special management concerns: Because so many bee species are found in riparian areas, protection of these habitats is obviously very important to native bees. Heavy recreational use of riparian forests could be damaging to native bees by removing snags and dead branches that serve as nesting sites. Chemical brush control over large areas would likely be harmful to native bees, as well as to other invertebrates.
Mutillid Wasps
Parasitic wasps in the family Mutillidae are commonly called velvet ants because of the soft- looking fuzz that covers their bodies. They may also be called cow killers or mule killers because the stings of some species are reportedly among the most painful of any insect. [The likelihood of getting stung, however, is quite low. Female velvet ants are wingless and have no hive to defend; almost all sting victims either grab or squish a velvet ant on the ground. Males have no stingers.] Velvet ants are most often encountered as solitary wingless females wandering on the ground or low vegetation; winged males also show up at lights at night.
Velvet ants reproduce by parasitizing the cocoons of other solitary bees and wasps in ground nests, wood tunnels, and mud or resin cells. Mutillid females spend most of their adult lives seeking out and parasitizing other bees and wasps, including the ground-nesting bees discussed above. Mutillid diversity is therefore tied directly to the region’s legendary local diversity of solitary bees. Some mutillids are generalists while others appear to attack only one or a few host species. Many species, however, are known only from wandering adults, so nothing is known about which hosts they might utilize.
Unusually high diversity: This region, and far southern Texas, are perhaps the prime areas for mutillid diversity in the United States. There is extreme local diversity in this region. Mutillid expert Don Manley has collected or identified in other collections over 50 species in the range. This is approximately the same number of species as are known from the entire eastern United States. The fact that over half the species known from the Peloncillos are represented by just one sex strongly suggests that many resident species have not yet been collected. As with native bees above, large year-to -year fluctuations in species’ abundances mean that it may take several seasons of collecting to find most of the mutillid species that live in the area.
Edge-of-range representatives: As with many other groups, this area does represent the edge of the ranges of many mutillids. The Peloncillo region includes several species such as Dasymutilla stevensii that reach their farthest south here. Dasymutilla magnifica and several more flow in from the western deserts to reach their farthest east here. Dasymutilla nigripes and others are mostly eastern species that “leak” across this low point of the continental divide.
Numerous Peloncillo region mutillids are primarily Neotropical, including Dasymutilla eminentia, D. apicalata, D. bonita, D. connectens, D. fasciventris, D. ferruginea, D. foxi, D. furina, D. intermixta, D. sicheliana, Ephuta tegulicia, Timulla coahuila, T. neobule, T. oajaca, T. suspensa sonora, and T. suspensa suspensa.
Endemism and evolutionary radiations: There are several species of mutillid that seem to be endemic to this area, although only one of these (Dasymutilla tomberlini) has been formally described. The Peloncillo region makes up a large part of the known geographic range of several other named species; 13 species are known only from Arizona and/or New Mexico, and 12 additional species are known just from Arizona, New Mexico, and Mexico. Another possible endemic is Aphonopelma n. sp. from Clanton Canyon. The scorpion Diplocentrus peloncillensis is not known to occur anywhere but in the Clanton Canyon area.
Other named species in the area appear to have differentiated into locally distinct populations. Manley notes that when specimens of these species are sent to him for identification, he can tell at a glance where a specimen was originally collected, within a 30-50 mile radius.
Special management concerns: These concerns are likely to be very similar to those for native bees, since mutillid larvae are parasites on native bees. The mutillid species with narrowly restricted ranges should be considered vulnerable to extinction. Several of these restricted-range species are quite numerous in this area. However, so little is known about the biology of these species that it is not at all clear what types of habitat alteration would constitute a threat to their continued existence.
Ants
The state of knowledge about ants in this region is an odd mix of rather little published data on diversity at specific localities, and a tremendous amount of long-term, in-depth knowledge about behavior, ecology, and natural history. While little collecting and no formal inventories have been conducted in the Peloncillo Mountains themselves, the neighboring San Simon Valley and Chiricahua Mountains are some of the best-known and most interesting ant communities in the nation.
Species diversity and composition: The Ants of New Mexico lists collecting localities in the Peloncillos proper for 54 species of ants. Collections at the University of Arizona and locality maps from Arizona State University38 added six more species. Quite a few of these species have been found just once in the Peloncillos, which suggests that many more remain to be discovered in this range. For five of these species, the Peloncillo region is the only place they are known to occur within the state of New Mexico. One, Temnothorax emmae (formerly Leptothorax) was known from nowhere else in the world until it was recently caught in the Chiricahuas. To get a sense for the level of diversity likely to be present in the evergreen woodland habitats of the region, a four-day study of a single small hill in the Chiricahuas yielded 30 ant species. All of these are likely present in the Peloncillos (although only 10 are yet reported from this neighbor range), as the study was conducted just 10 miles away within a range of elevation and plant communities that is common in the Peloncillos.
Valley faunas have received much more attention. Although no species lists have been compiled from these studies, a quick tally includes dozens of species. Robert Chew found an astonishing 23 species in a single 30-meter grid-study plot, in just eight days of sampling in a single season.
Various sources of evidence suggest that the Peloncillo ant fauna could exceed 200 species when the Sierra San Luis and Animas Mountains and flanking valleys are included. Ant researchers have found over 250 species in the Sky Island region. Based on their respective ecology and known ranges, most of these could easily occur within the greater Peloncillo focal area. A draft checklist of ants of Arizona lists 321 species. Of these, 187 have been found in the neighboring Chiricahua Mountains (many during ant taxonomy courses at the Southwestern Research Station). Virtually all of these Chiricahua ants could occur in the Peloncillo region, although high-elevation species would likely be restricted to the upper reaches of the Sierra San Luis and Animas Mountains. Many additional species could occur in the flanking valleys.
Ecology: Ants are a major part of virtually any area’s ecological dynamics. Rese archers estimate that ant biomass exceeds vertebrate biomass in most ecosystems, and that ant bodies make up some 10% of the Earth’s total biomass. In this part of the world, decades of studies have shown them to have a major influence on soil aeration and fertility, soil chemistry, seed dispersal and survival, dynamics of plant recruitment, rodent community dynamics, composition of other arthropod communities, arthropod herbivory, and so on. Several of these studies have been running long enough to show the effects of slow acting processes like climate change and to track long-term multi-species population cycles. These are a rare treasure in a world where only a small percentage of ecological studies last more than a few field seasons.
Behavior and natural history: Many of North America’s most interesting ant natural history and behavior stories have been discovered, and continue to be researched, in this area. For example, dozens of papers have now been published on the slave making ant (Polyergus breviceps), which cannot produce its own workers and instead raids the brood of several other local ants, then raises these as their own indentured servants and prevents them from breeding. The seed harvester ant Pogonomyrmex anergismus has ceased to harvest seeds and instead functions as a social parasite living inside the nests of related ant species and breeding in the corners of the host’s tunnels. Nature films and children’s magazines have made the region’s Myrmecocystus honeypot ants famous. The Peloncillos have at least four species of Myrmecocystus, which store sweet nectar in their own bodies. Honey-filled abdomens of these ants can reach an inch long, and make an irresistible treat to almost any animal that is lucky (or persistent) enough to find them—including humans with an adventurous palate.
Deborah Gordon’s 20-plus years of studying seed harvester ants in the San Simon Valley (near Rodeo, New Mexico) forms much of the foundation for our understanding of how ant societies function across the globe. Her book Ants at Work summarizes these understandings for the lay reader and is one of the most widely recommended books on invertebrate biology. Her work, in turn, builds upon the studies of one of the fathers of ethology, Bert Holldobler, who continues to study ants in the San Simon Valley and surrounding hills. Together with dozens of colleagues, this research group has published some 200 papers on ant behavior and natural history in this region—with far too many discoveries to summarize here.
This area’s neotropical affinities make it an especially fascinating place to encounter ants. Most people imagine finding army ants in the densest tropical rainforest. The Peloncillos, however, have at least four species of Neivamyrmex army ants, and probably more than 10. One of these, N. nigriscens, can reach colony sizes of over a quarter million individuals. Much of what we know about army ant behavior comes from studies in the bajadas of the San Simon Valley. This area also has leaf-cutter ants (Acromyrmex versicolor), close relatives to the ones featured in tropical nature shows. Just as they do in the rainforest, leaf-cutter ants here can defoliate entire trees to feed their huge subterranean fungus gardens (albeit smaller desert trees). One often comes across flotillas of bright petals and leaves skimming across the ground and disappearing into gravel craters, with a spiny ant hidden under each piece. Acromyrmex nests in the Peloncillo’s Granite Gap can show complexes of nest entrances that span more than 20 feet (6 meters) in diameter.
Special management concerns: Ants tend to be fairly robust to human activities, though ones with restricted ranges and narrow habitat preferences can still be vulnerable. Species currently known only from this area, or for whom this area constitutes a large part of their total range, should be evaluated to predict what activities might cause them harm.
Riparian species may be more vulnerable to human disturbance than others, simply because these habitats are so limited in arid western North America and because they are favorite places for humans to recreate, build, divert water, and otherwise alter habitat characteristics.
The other major threat to such communities is invasion by exotic species. Whole communities of native ants in the southeastern United States—and other native invertebrates and vertebrates alike—have been devastated by the invasion of the imported fire ant Solenopsis invicta (also known as Solenopsis wagneri). In 1985 this ant established a small population at Stein’s Pass; luckily it was found early and could be exterminated before it spread. So far, no other reports of S. invicta have surfaced here, but they should be considered a serious threat. Some researchers suggest that S. invicta would have difficult time establishing in places as arid as is much of the Peloncillo region. Others dispute this, citing the fact that this invader has already spread past what were initially considered to be its ecological boundaries. Regardless, the region’s riparian areas would be especially vulnerable to invasion by this or other exotic species. The region has at least one native fire ant that looks quite a bit like S. invicta; identification of Solenopsis species should be done with care to avoid false positives while still making sure invasions are detected early.
Order Odonata: Dragonflies and Damselflies
The jewel-like dragon and damselflies have begun to vie with butterflies for the attentions of popular bug-watchers. Because of this, and because odonates have long been recognized as indicators of water and aquatic habitat quality, local species lists and regional distribution maps have been improved greatly in recent years. Odonate-hunters are often still rewarded for their efforts with rare species, new localities, and range extensions.
All dragonflies and damselflies have aquatic larvae and therefore need water sources to breed. Some require perennial streams, others lakes or ponds; several rapid-developing species can even breed in temporary pools. The Peloncillo region has an abundance of ephemeral pools, quite a few perennial stock ponds, several springs, and, in Mexico, both perennial streams and hot springs. The lack of year-round flowing water in the U.S. -portion of this focal area obviously limits the number of odonates that can breed on this side of the border. Adults of many species, however, are strong fliers and can be found miles from the nearest water. Some species found as adults in the Peloncillo Mountains proper may therefore be emissaries from creeks in nearby ranges, or across the border.
As with many other invertebrate taxa, most of the focal area has not been formally surveyed for dragonflies or damselflies. The San Bernardino NWR, however, has attracted many odonate researchers, who report an impressive total of 28 damselfly and 40 dragonfly species from its relatively small management area.
The states of Sonora and Chihuahua are far undercollected for odonates, but this situation is beginning to change. Collections done on the behalf of the Cuenca Los Ojos foundation in and around Cajon Bonito (in the Sierra San Luis) and the Rancho San Bernardino property (adjacent to the San Bernardino National Wildlife Refuge) have found 55 odonate species. 18 of these have not yet been reported from the US portion of the Peloncillo region.
In adition to species now reported from the Peloncillo region, a Cochise County odonate checklist adds another eight species to the species pool of possible residents, and a new website of New Mexico odonates adds nine more known from Hidalgo County or nearby, bringing the known local species pool to 106 species (note that New Mexico is poorly collected compared with Arizona, so county lists are much less complete). These are listed here as possible residents. Range maps of several additional species overlap or come very close to the Peloncillo region.
Biogeography: The majority of odonates reported from this area have primarily southern distributions (below). Several others are Western specialists, such as the California spreadwing (Archilectes californica) and the California dancer (Argia agrioides). A few more Boreal species find their southern limits here, including the Plains forktail (Ischnura damula). Eastern specialists are scarce, probably because this arid zone offers few of the wet habitats these insects are adapted to on the rainy side of the continent. Some have very broad distributions, like the dusky dancer (Argia translata), which ranges from southern Canada to Argentina, and the American rubyspot (Hetaerina americana), which occurs throughout North America.
Neotropical representatives: As mentioned above, many of the odonates in this area are predominantly tropical. Neotropical dragonflies include the malachite darner (Coryphaeschna luteipennis), the spotwinged meadowhawk (Sympetrum signiferum), and the plateau dragonlet (Erythrodyplax connata ). Several damselfly species are primarily Mexican species that extend north into southern Arizona, e.g., the Sierra Madre dancer (Argia lacrimans), the Aztec dancer (Argia nahuana ), and the claw-tipped bluet (Enallagma semicirculare). Others range far into Central America, such as the spine-tipped dancer (Argia extranea) and the black and white damsel (Apanisagrion lais). The canyon rubyspot ( Hetaerina vulnerata) ranges all the way to Brazil.
Endemism and taxa with limited ranges: While several Arizona and New Mexico damselfly species are endemic to small areas, none of these is yet known from the Peloncillo region. Several of the species in this general area, however, do have limited known distributions. The desert shadowdamsel (Palaemnema domina), for example, has never been found in the U.S. outside of Arizona’s Graham and Cochise counties.
Conservation notes: The odonate diversity of this area is quite remarkable, especially considering the scarcity of perennial waters. Odonate experts are lauding land and water protection efforts in the US and Mexico for their roles in maintaining this diversity. Said Sandy Upson to Joe and Valer Austin of the Cuenca Los Ojos foundation, "the demonstrated continued health of populations of Argia lacrimans, A. tarascana, Macromia magnifica and Dythemis maya, among others, establish Cajon Bonito as being among the most important Odonata centers in Sonora and arguably in northern Mexico. Since dragonflies serve as indicators of the good health of ecosystems, your own efforts are clearly having a major effect. Thank you again!"
Order Coleoptera – Beetles
The order Coleoptera is one of the three largest insect orders, with global species estimates ranging into the tens of millions. At this point in time, beetle species lists for the Peloncillo region would be exceedingly long, woefully incomplete, and largely uninformative. A few anecdotes and general comments, however, may help set the stage for future examination of the area’s beetle fauna. In addition, one relatively tractable and more thoroughly studied group, tiger beetles, is reviewed in detail below.
Two nearby sources of data may give a sense of the magnitude of beetle diversity present across this region. Collections at the University of Arizona catalog some 400 beetle genera from the Willcox Playa. Over 100 of these were collected by one researcher during a single season of sampling. Most of these could also occur in the Lordsburg Playas area. The family Cerambycidae (longhorn beetles) is one of the largest groups in many forested regions. Linsley et al. report 132 species from the Chiricahuas (including San Simon Valley localities), including photographs and natural history information for many of these. The University of Arizona collections list some additional 30 species. The authors consider almost half of these to be more - or-less endemic to the Sky Island region, and most seem to be on more than one range (e.g., species reported most from the Huachuca Mountains have also been found in the Chiricahuas). Most of the Chiricahua species could occur in our focal area, although the high-elevation species would likely be relegated to the Animas and Sierra San Luis peaks.
Several suites of beetle species from various families—including Cerambycidae (longhorn beetles) and Elateridae (click beetles)—are adapted to fire. Many of these species reproduce only in burned forests of various ages, some only in trees that are still warm from the smolder and others in a successional series as the burnt trees age. Many of these species are rare in collections because of their ephemeral presence. This has raised concern that some may be vulnerable to extinction, although the fact that they must be very good dispersers to track their ephemeral habitats may buffer them from extinction. The return to a semi-natural fire regime is likely be very beneficial to these beetles, as well as to other fire-adapted insects.
The UA collection reports 60 native bark beetle species (Scolytidae, though many scolytids do not attack trees) from the Chiricahuas, many of which must also occur in the Peloncillos. Some, but not all, bark beetle species naturally experience large population fluctuations that are termed “outbreaks.” Outbreaks of bark beetles have raised concern throughout the West. Most of the outbreaks are resolved as the beetles’ natural predators (primarily parasitoid wasps but also birds and other insectivores) bring the populations back down to a level at which humans fail to notice their continuing effects. These beetles can cause large local die-offs of certain tree species, which can harm other wildlife that depend on forests. Tree die-offs are also visually alarming to people, and may increase fire risk, which is viewed very negatively when there are human habitations nearby. While such population fluctuations are a natural part of the dynamics of both beetles and forests, there is considerable evidence that some of these fluctuations have become more severe and/or more widespread than they have been in the past (i.e., are outside the normal range of variation). Much of this change is attributed to drought, tree overcrowding, fire suppression, and/or global warming. Carefully thinning overcrowded trees in particular areas may reduce beetle kill in future outbreaks by giving remaining trees more resources to defend themselves, but harvesting infested trees has limited effectiveness in stopping or slowing spread or intensity of an outbreak. Returning to natural fire regimes is probably the most effective and economical means to reduce severity of bark beetle outbreaks in regions such as this.
Another noteworthy event is the apparently recent invasion of the area by the introduced dung beetle Onthophagus gazella. This beetle was first noticed in southern New Mexico several years ago, and has been gradually reported from a broader and broader area since then. David Richman at New Mexico State University states that he had not seen many in the Peloncillos until this year, although they may have been here somewhat longer. The UA collection lists 15 species of native dung beetle from the Peloncillos and 24 from the Chiricahuas (many of which probably also occur in the Peloncillo region). This introduced species has the potential to out-compete some natives, particularly congeners with similar habits and body sizes. The process of community change with invasion would be fascinating to document, although there seems little hope of altering its course since there are no known methods for controlling dung beetles (which are beneficial to nutrient cycling and therefore not generally considered pests, even as non- natives).
Tiger Beetles
Some 111 tiger beetle species are found in North America. Most are restricted to environments with access to open ground, including stream edges, saline flats, seashores, and sand dunes. Although mostly small in size, tiger beetles are important predators of the insect world. Their beauty, diversity, and wariness make them a favorite among collectors worldwide. Besides their appeal to collectors, researchers find tiger beetles to be excellent models to study community ecology, biology, morphology, thermoregulation, predator-prey interactions, biogeography, and physiology. Because of these factors, tiger beetles are one of the best studied non-pest insects. Tiger beetles are also easily studied bioindicators of environmental quality. The presence or absence of certain species can provide information on the quality of the habitat, successional stage of the habitat, and/or alterations to the habitat. Because of their restricted habitat requirements, tiger beetles are sensitive to environmental degradation, and several species and subspecies are state or federally protected.
Adult tiger beetles are active pursuit predators that hunt on open substrates where can they use their excellent eyesight to locate small arthropod prey, then chase down prey on foot or on the wing. They are legendary for their speed and agility; because of these abilities, catching tiger beetles is considered a great challenge for amateur and professional entomologists alike. Many species are brilliantly colored. Others are well -camouflaged; populations of cryptic species may vary in color according to the soil colors in particular areas. About three-fourths of the tiger beetles in North America belong to the genus Cicindela. Species can be distinguished by differences in size, coloration, and markings on their wing covers.
Tiger beetle larvae typically occur in the same location as adults. The adult female selects a spot to lay her eggs, excavates a small hole up to a centimeter deep, deposits a single egg, then covers the hole. Females are extremely selective in choosing oviposition sites, with each species following its own set of preferences. Preferences are so narrow that one rarely finds more than one species of larva in the same site, even where adults of several species are present. After hatching, the larva digs a cylindrical burrow at the site of oviposition. Larvae are also predators, but rely on ambushing their prey from the mouths of these burrows. How quickly larvae develop depends on climate and food availability, and most take two to three years to reach adulthood. The prolonged and sedentary life cycle exposes the larvae to environmental stresses including flooding, drought, and ground disturbance.
Biogeography: Of the tiger beetle species in the U.S., almost half (48 species) live in Arizona and/or New Mexico (32 of these occur in both states). Several of these are divided into multiple subspecies; including these subspecies, New Mexico has a total of 64 taxa, more than any other state in the nation. At the species level, 15 are known to occur in the Peloncillo area, with six to eight more considered likely to be found with more collecting. This high diversity can be attributed to the intersection of faunal provinces and to the amount and diversity of arid, open habitats in the region.
Tiger beetle diversity across this region is fairly well documented, though locality information can be spotty. Within New Mexico, however, the southwestern corner of this state remains under-represented. Southeastern Arizona has hosted some excellent studies on tiger beetle biology. The Sulphur Spings Valley (one valley west of the focal area), is considered a “hotspot” for tiger beetle diversity, with documented richness of up to 17 species in and around the salt flats of the Willcox Playa. However, claims about diversity and distributions sometimes conflict with one another. One agency document reports there being 40 species of tiger beetles there (with no supporting documentation or taxon lists), more than are otherwise reported from the entire state. This appears to refer, in reality, to total taxa, including more than one subspecies for several species.
Edges of ranges and neotropical representatives: As with many other taxa, the Peloncillo region is near the edges of ranges for several tiger beetle species. Cicindela wickhami, for example, is predominantly a Sonoran Desert species, nearing its eastern edge here. The range of C. debilis tracks that of the Chihuahuan Desert, which brings it near its northern and western edge here. The Peloncillos lie at the south end of the ranges for C. willistoni and C. oregona, and the north end of the ranges of C. viridistica, C. wickhami, and C. fera. Several of the region’s tiger beetles are predominantly neotropical, reaching their northern limits in this area. These include C. viridistica, C. fera, and C. debilis. The genus Tetracha (sometimes included under Megacephala) is a primarily tropical genus, with 10 species and six additional subspecies in the tropics and subtropics of Central America and the Caribbean, and two species in the United states, including T. carolina in the Peloncillo region.
Endemism and taxa with limited ranges: There are no tiger beetle species that are known to be strictly endemic to the Peloncillo region (the geographic area as defined in this report), although Cicindella pimariana comes close, being known only from the far southeast corner of Arizona and far southwest corner of New Mexico. For several other species this region makes up a large portion of the species’ known range. These include Amblychela baroni, Cicindela fera, C. horni, and C. viridistica. Saline species, including C. willistoni and C. nevadica thought to occur here, exhibit a tendency to form restricted-range subspecies. However, southwestern New Mexico has not been well enough studied to reveal the local diversification patterns in these species.
Special management concerns – tiger beetles: Fire supression, development, invasion by non- native weeds, livestock grazing, altered hydrologic cycles, and off-road driving are the activities with the greatest potential to affect tiger beetle species in this area. However, because most tiger beetles need open ground, some moderate-intensity ground-disturbance activities may be positive, at least in certain circumstances.
Direct effects of fire on tiger beetle individuals is not well known, although fire suppression has been implicated in the decline of rare species. Numerous studies report tiger beetles becoming more abundant in an area following fires that open up ground vegetation.
For salt-pan and water-edge species, any activity that changes hydrologic patterns is highly likely to affect the species. Impact to dune-dependent tiger beetles caused by stabilization or destabilization of dunes is well documented. No dune species are currently known from the Peloncillo region, but appropriate habitats have not yet been well surveyed.
Off-road driving has been implicated in the decline or local extirpation of some tiger beetle species. However, because such driving destroys vegetation and leaves bare soils, it has boosted populations of some tiger beetles in heavily vegetated areas. In cases where fire supression or invasive weeds have allowed vegetation to exceed natural levels, off-road driving and other ground-disturbing activities appear to have helped certain tiger beetle species by opening up more bare ground. Such positive effects are not expected in this arid environment. Grazing does not tend to harm adult tiger beetles, but can trample larvae in their burrows if use is heavy in prime beetle habitat. However, moderate grazing can also maintain open ground that may benefit particular species. Effects on species with restricted ranges and/or narrow habitat preferences should be examined on a case-by-case basis.
Appendix G lists species known to or strongly suspected to occur within the Peloncillo region, along with typical habitat characteristics. Two of these (Amblycheila baroni and Cicindela horni) are tracked by the Arizona Game & Fish Heritage Management Database as species of interest, presumably because of their restricted ranges (although the choice of these two and omission of species such as C. pimeriana, which has an even more restricted range, seems rather arbitrary). None are officially species of concern by any entity catalogued in the New Mexico or Arizona heritage databases.
Special management concerns - Coleoptera: With the magnitude of diversity in question, few specific concerns can be addressed, apart from recognizing the special value of riparian areas, and the value of fire to both certain beetle groups and to forest dynamics influenced by bark beetles.
A few species of beetle in the region are considered sensitive or species of concern by various entities. The only one documented from this region is the Animas minute moss beetle (Limnebius aridus), listed as a species of concern by the state of New Mexico, New Mexico BLM, and U.S. Fish and Wildlife Service. The Center for Biological Diversity lists it as having gone extinct. Little is known about this species apart from its original taxonomic description.
Beetles of this genus often hide in moss or algae at the edges of springs, marshes, or streams. Because of their small size and secretive nature, they are easy to miss in collecting.
Order Lepidoptera – Butterflies and Moths
Butterflies
Their bright colors, large fan base, and importance as pollinators make butterflies a flagship group for invertebrate conservation. More is known about butterfly ranges and habitat needs than about the needs of any other large invertebrate group. Still, the fauna is so rich that much remains to be discovered.
Unusually high diversity: The Sky Island region’s remarkable butterfly diversity attracts enthusiasts from around the world to southeastern Arizona and southwestern New Mexico. Although few published lists exist for specific localities in this focal area, regional butterfly diversity patterns can help fill in the gaps, even where we lack data for particular localities. With just one small formal study published, more than 133 species of butterflies have already been reported from the U.S.-portion of the Peloncillo region, plus an additional 87 species reported from the Rancho San Bernardino immediately adjacent to San Bernardino NWR on the Mexican border.76 Since the species list for Cochise County exceeds 240 species, and the Gray Ranch list already includes eight species not on the Cochise County list, local butterfly experts predict that more study could easily bring the official U.S. portion’s total past 200. If the Sierra San Luis and its riparian drainages were included, the area’s butterfly list could exceed 300 species.
Neotropical representatives: Southern affinities of the range are strong, especially at the south end of the Peloncillo Mountains, with species like the tropical checkered skipper (Pyrgus oileus) and Erichson's white-skipper (Heliopyrgus domicella). Guadalupe Canyon has been a favorite butterfly-watching site for decades. Because this wet canyon opens to the south into Mexico’s large Río Yaqui drainage, it is an excellent place to find wandering tropical butterflies. In formal terms, “this canyon is one of the very best influx traps in the region and has a variety of strays rivaled only by Sycamore Canyon” (in Santa Cruz County, Arizona; the most famous butterfly site in Arizona, and one of the best in the nation). Butterflies of Arizona notes of Sycamore Canyon: “It is here that one can feel the breath of the Neotropics from mid-June to September, when the land turns green and the sun angels in their countless thousands dance and glide though the air, bringing us dreams of those magical lands to the south.”
Migratory species: Many butterfly species make at least short-distance movements at particular times of the year. Individuals will travel to find mates, to find adult foods (puddles, flowers, etc.), to find fresh host plants for their larvae, and, in some species, to overwinter in warmer or more sheltered habitats. Only these last are considered fully migratory.
The Peloncillos are tropical enough to host year-round populations of several species that are migratory in other parts of the U.S. The painted lady (Vanessa cardui ), for example, summers throughout the Americas. In winter, these lovely butterflies retreat to the south where they will not freeze. The Peloncillos lie in the very northern edge of the painted lady’s wintering grounds; it is from these wintering grounds that they spread each spring to repopulate the rest of North America.
Other species require even milder winters, so are found here only in the warmer months. The large orange sulphur (Phoebus agarithe), for example, winters in coastal and central Mexico (and south Florida), and graces this area with its bright tangerine wings only during summer monsoons. Another special migratory member of this fauna is the southern snout butterfly (Libytheana carinenta larvata). This species winters in Mexico, and each spring its northbound flights fill the San Bernardino Valley with thousands upon thousands of fluttering bodies.
The monarch (Danaus plexippus), most famous of all migratory butterflies, meet each winter in two main areas: the mountains of Michoacan, Mexico, and the central Pacific coast of California. It was long thought that all monarchs raised east of the Rockies wintered in Michoacan, and those west of the Rockies wintered in California. It is now clear that this “great divide” is a myth, and that at least some individuals cross back and forth between eastern and western populations. The details of these exchanges, however, are not well understood. The Peloncillo region—sitting at the low spot of the Continental Divide—seems a likely place to find monarchs crossing between populations, and would be a valuable place to include in the ongoing efforts to track movements of individual butterflies. Guadalupe Canyon is thought by many to be an important migration route,84 and anecdotal evidence already suggests that at least some monarchs in this region may be headed towards Michoacan rather than California.85 If the area is a significant crossover-zone, it may be important to the genetic exchange and metapopulation structure of these eastern and western monarch populations.
Special management concerns: Because a fair amount of information remains to be learned about butterfly populations and ecology, management will continue to be a challenge. Caterpillar ecology and host plant use are poorly understood for many species. As mentioned above, migration patterns are also poorly understood. No inventories have been conducted in the higher elevations of this area. The boreal fauna is therefore unknown. This should be a priority, since high-elevation butterflies are thought to be particularly vulnerable to forces such as climate change because of their lower tolerance for warming and the disproportionate loss of high- elevation habitats in isolated mountains such as these. None of the butterflies known to occur in this region is federally or state listed as endangered or threatened. However, several species are considered vulnerable by one entity or another, and a number of general recommendations can be drawn for the fauna as a whole. The Prittwitz’s skipper (Adopaeodes prittwitzi) is a cienega specialist known from springs in southeastern Arizona and southwestern New Mexico, including the Gray Ranch. A. prittwitzi caterpillars are only known to feed on knotgrass ( Paspalum distichum). The species has no formal concern status, but is nevertheless of conservation interest to the Arizona Game & Fish Department, which recognizes how vulnerable the species is to continued degradation of spring systems.
The U.S. Forest Service recognizes a number of sensitive butterfly species in Region 3. These include several Agathymus skippers, the larvae of which bore into the leaves and stems of agaves. Agathymus aryxna is known from the focal area, with A. polingi reported but unconfirmed. These species have narrow distributions, but appear to maintain healthy populations wherever their agave hosts occur. The blue silverspot butterfly ( Speyeria nokomis coerulescens) is a high -elevation butterfly that appears to be extirpated from the U.S. It or other subspecies could occur in the Sierra San Luis, but the range has not been adequately surveyed.
The viceroy butterfly (Limenitis archippus obsoleta) depends on willow thickets for its larval growth, and has been reported from the San Bernardino springs and the Gray Ranch. Although widespread, this butterfly is considered to be at risk of extinction because so much of its riparian habitat has been lost or degraded. Across its range, some of this habitat loss has come at the hands of the invasive tamarisk tree, which has replaced many cottonwood and willow stands across the West; some has come at the hands of water diversion, overgrazing of riparian areas, and development. Keeping tamarisk out of this area and otherwise maintaining willow thickets will be a boon to the species.
Just one species known from the area has a Heritage Ranking of G2 (Rare/Imperiled) on the global and state (Arizona) scale: the Arizona metalmark butterfly (Calephelis rawsoni arizonensis), a resident of low mountains including parts of the Gray Ranch. Global G3 (Uncommon or Restricted) species reported from this area are Chiricahua pine white butterfly (Neophasia terlootii ), a mid-elevation species well-known in the Chiricahua Mountains with unconfirmed reports from the Animas Mountains; and the Pima orangetip butterfly (Anthocharis pima), a desert and foothill species known throughout the Sky Islands, including Cochise and Hidalgo Counties. The cyna blue butterfly (Zizula cyna) and the definite patch butterfly (Chlosyne definita) are known from nearby counties and may also occur here.
In more general terms, all herbivorous insects depend on finding adequate populations of their host plants. Maintaining ecological processes that sustain plant diversity therefore helps protect insect diversity across the spectrum. Conversion of botanically diverse communities such as open savannas, prairies, grasslands, and woodlands to less-diverse stands dominated by shrubs, trees, or invasive weeds tends to reduce butterfly diversity, sometimes dramatically so. Unless species have been extirpated from a large area, butterfly diversity often rebounds when natural stand structure is restored via fire or other methods.
While restoration of natural plant community structure is generally beneficial to butterfly assemblages as a whole, one must keep in mind that restoration methods (e.g., fire and mechanical thinning) can affect individual species differently in the short term. Species whose habitats are highly fragmented (naturally or as a result of habitat loss) can be vulnerable to direct mortality and short-term loss of food plants from fire. Butterflies are sensitive to changes in microclimate, so thinning of trees or shrubs can affect them directly (positively or negatively). Declining numbers of particular plants can doom butterfly populations that depend on them, as in the case of the Viceroy above. Any effort to maintain a rare plant species or plant assemblage has the potential to rescue its associated butterflies (and other insects) from decline as well.
Nectar-producing flowers are a resource used by many, many species. Any areas with especially abundant and diverse flowering plants, e.g., riparian areas, are therefore of particular value for butterflies. Migratory species are especially dependent on such “nectar corridors” to fuel their long-distance flights. Any factor that degrades or interrupts these flower swaths, or makes them hazardous to insects, will harm butterfly populations. Activities such as dewatering of streams and widespread application of pesticides in riparian areas or along flowering roadsides should obviously be avoided.
Extensive use of pesticides—and transgenic crops that produce their own pesticides—has caused problems for butterflies in some areas. Peloncillo-region agriculture is now fairly limited, so the area’s isolated pesticide use in small patches of cropland is probably not a major threat to butterfly species in general. Nevertheless, some species whose host plants occur in or at the edges of fields may be affected. Some studies have found that monarch caterpillars are poisoned by toxic pollen from transgenic corn when the wind-borne pollen falls on their milkweed host plants (though other studies debate how significant these effects are in natural settings). It is not known whether corn crops here are transgenic, though these varieties have become very widely used. This area harbors several milkweed species, including both field species and others that grow in natural areas away from croplands; caterpillars feeding on the latter should not be affected by agricultural activities.
Global climate change has already begun to affect butterfly distributions and life histories.94 Maintaining north-south movement corridors and connections between natural habitats at all elevations will help taxa like butterflies to adjust their ranges as conditions shift. Because of this region’s elevational gradients and its location at the edge of many species’ current ranges, it would likely be a very informative place to study such range shifts. In time, this region may well lose some of its northern and upper-elevation species, but it may also provide refuge for tropical species that do not yet occur here. Climate change may also alter migration patterns of some species.
Moths
No data have yet been compiled on moths, but entomologists expect, as a rule of thumb, that the number of moths in an area will be ten times that of the butterflies. This brings a staggering prediction of 2,000-3,000 moth species in the Peloncillo region. Management concerns would be similar to those for butterflies. In addition, large continuously run lights (such as are used in some border surveillance operations, typically in densely populated areas) could be a significant population sink for rare species that are strong fliers.
Order Orthoptera – Grasshoppers, Katydids, Crickets, and Mantids Grasshoppers are very diverse in this region, and are ecologically interesting because of their roles as herbivores of grasses, shrubs, and forbs. No formal inventories have been done for the region, although the grasshopper fauna is fairly well known. The New Mexico Natural Heritage species list for Hidalgo County includes 86 species, almost all of which could occur in the Peloncillo region. Most are not thought to be significant pests, and several that eat common plants unpalatable to livestock are considered beneficial to rangelands, including the snakeweed grasshopper (Hesperotettix viridis) and the creosotebush grasshopper (Bootettix argentatus).
Crickets and katydids are less well studied; no regional species lists are available. Other orthopterans of interest include several species of praying mantis. Most but not all mantids are widespread species with broad habitat requirements. Some entomologists in the region consider the unicorn mantis (Pseudovates arizonae) a species of concern due to its rarity and localized distribution; this species has been found in the southern Peloncillos. This rare, local endemic is known only from local and geographically separated populations. Restricted to dense riparian vegetation habitats, P. arizonae is potentially threatened by domestic livestock grazing and water developments, as well as competition from exotic mantids intentionally released for garden pest control. These include the Chinese and European mantids, which are becoming naturalized throughout the United States.
Another rare, regionally endemic mantid may occur in the higher elevation grasslands. Stagmomantis gracilipes is known from south-central Arizona (including the Baboquivari, Patagonia, and Santa Rita Mountains, and near Benson and Tucson), and probably also occurs in northeastern Sonora. S. gracilis appears to be restricted to high-quality native upland grasslands, which have declined drastically in the Southwestern US. Its main threats appear to be habitat degradation and loss, and potentially competition from exotic mantids.
Nearby ranges (Santa Rita and Santa Catalina Mountains) harbor an endemic high-elevation walking stick, Timema ritensis. Collectors working in the high forests of the Animas and Sierra San Luis should be on the lookout for this and related species.
Biogeography: As with other invertebrate groups, several grasshoppers near their northern limits here. One of the most handsome examples is the panther grasshopper (Poecilotettix pantherina), which ranges through Sonora and southern Arizona grasslands eating shrubs and forbs in the sunflower family. The aptly named toothpick grasshopper (Achurum sumichrasti) a nd the huge horse lubber (Taeniopoda eques) range all the way to Costa Rica. The slender range grasshopper (Acantherus piperatus) is predominantly a species of western Mexico.
Endemics and restricted range species: No strict endemics are known from this region. However, the lichen grasshopper (Leuronotina ritensis) is known from just a few localities in the U.S., including the Animas and Peloncillo Mountains. This rarely seen species has also been found in the Santa Rita Mountains, and two sites in Mexico (Sierra de los Ajos, Sonora, and Basaseachi National Park, Chihuahua). L. ritensis eats Xanthoparmeli lichens on rocky outcrops in mountains above some 6,000 feet elevation.
The Apache bush katydid (Insara apache) is another possible restricted-range resident, known now only from perennial bunchgrasses in the mid-elevation slopes of the Santa Catalina, Santa Rita, and Huachuca mountains. The pinyon pine monkey grasshopper (Eumorsea balli), known only from the Huachuca, Pinaleño, and Santa Rita mountains, may also occur here. Several endemic grasshoppers are known from nearby ranges, suggesting that additional survey work may turn up endemic species within this focal area as well. These include Melanoplus chiricahuae known only from the nearby Chiricahua Mountains, M. pinaleño and Eumorsea pinaleño from the Pinaleño range, and Aztecacris gloriosus from the Atascosa Mountains.
Cave-dwelling camel crickets also tend to have high rates of endemism. The genus Ceuthophilus has several species (C. chiricahuae, C. tinkhami, C. baboquivariae, C. papago, and C. wheeleri) known from just one or two Sky Island ranges; these first two live in the Chiricahua Mountains. Suitable habitats within Peloncillo region have not been surveyed.
Special management concerns: Because some grasshoppers can consume significant amounts of crops and range forage, they may become targets of control efforts using pesticides and/or biological control agents such as fungi and protozoan parasites. Most pesticides used for grasshoppers also kill a wide spectrum of other arthropods, including beneficial insects such as the parasitic and predaceous flies that attack grasshoppers and help keep outbreaks from occurring in the first place. Biological control agents are more targeted, but still kill innocuous and beneficial orthoptera along with the pest grasshoppers. This area is host to a large number of species that are rarely, if ever, significant pests to range or crops, and that may help maintain plant diversity across the landscape. Populations of all these species fluctuate naturally, though some more widely than others. In assessing possible “grasshopper outbreaks,” care should be taken to avoid confusing population surges of beneficial or innocuous species with “infestations” of pests.
ARACHNIDS
Order Scorpiones: Scorpions
High diversity: For scorpions, the general area presents an "interdigitation effect" of the Chihuahuan and Sonoran Deserts. In the flats, there is a tendency for Chihuahuan species to predominate; in the outcrops, the Sonoran species predominate. These divisions, however, are not absolute. One exception is the tiny chocolate-colored Sonoran desert scorpion Superstitionia donensis, which has been taken in the San Bernidino Valley. Extensive survey work in the "bootheel" area of New Mexico, conducted by Sissom and colleagues, has turned up 13 scorpion species. At a single sampling site with diverse habitat, one can find up to nine of these. This is very high diversity for North American scorpions. Big Bend National Park lists about 15 and the Anza Borrego Desert reportedly has around 20 or so. Average sites across western North America list between four and six species.
Endemism and evolutionary radiations: Two endemic scorpions are known from the Peloncillo Mountains proper. One, an undescribed Vaejovis species (descriptions by W. D. Sissom are in manuscript form) is known only from Granite Gap. The unusually handsome Diplocentrus peloncillensis is also endemic to the range.
Perhaps most striking examples of regional diversification are the members of the Vaejovis vorhiesi “complex.” These small scorpions are found at higher elevations in the Sky Islands throughout central and southern Arizona and western New Mexico. They are all very similar, but there is at least some differentiation in the different mountain systems.
Order Araneae: Spiders
Very little spider research has been done in the mountains of the Peloncillo region. One major exception to this is David Richman’s ongoing spider inventory on the Gray Ranch, including the east slopes of the Peloncillos, the Animas Valley, and the west slopes of the Animas Mountains. So far, this work has revealed over 100 species, with no indication that the list is nearing completion; indeed, new species still turn up in every collecting trip.
The spider fauna of the Chiricahua Mountains, however, is better studied than almost anywhere else in the West. As of 1977, this fauna was known to contain a minimum of 363 species in 36 families—including most of the families present in North America. Among these were at least 45 species that were clearly new to science and another 36 that could not be placed to species. About 30 of these species have since been described or assigned to known species, mostly based on Vince Roth’s collections and those of a few people who have followed him in Chiricahua spider studies. By 1996, Roth had found another 40 species in the range, but unfortunately did not live to publish an update to the Chiricahua list. He did, however, leave a legacy of spider research that continues to this day, with dozens of researchers having studied spider ecology and behavior in the Chiricahuas and the San Simon Valley.
Endemism and evolutionary radiations: An Aphoenopelma tarantula species that appears to be new to science has recently been discovered in the Peloncillos proper. While new species are common in other spider groups, tarantulas have received enough attention in the past that a new species in the U.S. is quite a remarkable find.
Specimens of the Sky Island jumping spider Habronattus pugillus have also been found in the Peloncillos proper, in a side canyon off of Clanton Draw. This oak woodland spider has isolated populations on at least 18 Sky Island ranges. Each population is adorned with its own distinct set of courtship ornaments, and males on each range perform their population’s own unique dance for their females. The Peloncillos form, discovered in 1998, differs from all other population most strikingly in having shiny butterscotch-colored p edipalps, which males wave prominently during their courtship displays.
Other Arachnid orders
This area is home to some of the strangest-looking arachnids in the nation. The vinegar-shooting whip scorpion (Arachnida: Uropygi, Mastigoproctus giganteus, aptly called the vinegaroon) is fairly common in the valleys and foothills, where it can exceed five inches in length, plus tail. Windscorpions (Arachnida: Solifugae) are also common, with several species across various habitats and elevations. Tailess whipscorpions (Arachnida: Amblypygi) likely occur here as well. Mites and ticks (Arachnida: Acari) occur virtually everywhere on the planet. This area’s most conspicuous members are velvet mites––plush, dimpled red animals that can reach over a centimeter in length. Velvet mites become active after the first summer rains, when they can be seen wandering across the ground in search of termite prey.
MYRIAPODS
This area is home to some of the continent’s most conspicuous centipedes and millipedes. Centipedes can be recognized by having just one pair of legs per segment, and despite their name (“100 legs”), most have only about 30. Four superfamilies of these predaceous animals live in the Peloncillo region: Scolopendromorphs are the largest and best-known. Spec ies recorded from this area include Scolopendra heros, S. polymorpha, and S. viridis. S. heros, sometimes called the giant redheaded or giant desert centipede, can reach almost 20 cm in length, and can inflict a painful but not dangerous bite. S. heros comes in several color forms across its range; the Peloncillo Scolopendra heros is orange with black head and hind end.
Scutigeramorphs such as Scutigera coleoptera, the American house centipede, have much longer, more delicate legs, with a maximum of 15 pairs. The eyeless Geophilomorphs tend to live in leaf litter and humus and have more legs than other centipedes—as many as 177 pairs. Lastly, the Lithobiomorphs tend to be found among rocks at high elevations. These orange- brown centipedes resemble small versions of Scolopendromorphs.
Millipedes, with two pairs of legs per segment, are detritivores. The giant desert millipede (Orthoporus ornatus ) can grow to more than 10 cm. O. ornatus and similar species are sometimes kept as pets (as is S. heros) and are offered for sale by several collectors. Orthoporus millipedes can be quite abundant in this area and may cover the ground by the thousands after good summer rains. The area undoubtedly harbors many other kinds of millipede, but little information exists about this globally under-studied group.
CRUSTACEA
Branchiopod Crustaceans
When one thinks of crustaceans, dry mountains and grasslands are hardly what comes to mind. But within days of a filling rain, this area’s alkaline playas, stock ponds, seasonal washes, rock holes, and other puddle-forming sites begin to fill with small crustaceans. When a pool dries, these animals return to a state of suspended animation until their pool refills—perhaps many years in the future.
Branchiopod crustaceans, including fairy shrimp (Anostraca), tadpole shrimp (Notostraca), clam shrimp (Diplostraca), and cladocerans (Diplostraca) make up a large fraction of the animal life that depends on such temporary waters. When conditions deteriorate (e.g., when a pool dries, predators appear, or competition increases), most have the ability to dry up into tiny, dust-like cysts that remain in the soil. Cysts can remain viable under extreme cold and heat (including fire) for up to several decades, forming a “cyst bank” very similar to the long-lasting seed banks of desert annual plants. When pools fill again and conditions are right, these cysts hatch, instantly filling the new pools with a complex suite of swimming animal species.
Individual pools usually have just a few dominant species at any given moment, presumably because coexistence is limited by competition and predation among species, and by the fact that each species emerges only under a limited range of conditions. However, sampling a single pond across time or a set of nearby ponds at one time can yield a dozen or more species representing several different crustacean orders. This is much more diverse than a comparable permanent pool or stream, perhaps because the ephemeral crustaceans, like desert annual plants, become segregated in time as well as space.
Branchiopod biogeography is rather complex. Arid western North America is considered a global hotspot for fairy shrimp diversity. Of some 300 species in the world, 30 are found in western North America; half of these are endemic to this part of the continent. Within the West, many species are endemic to very small areas, and even widespread species can show a high degree of genetic structure (e.g., residents of one pool may be genetically distinct from those in a pool just a hundred meters away). This differentiation is presumably due to the patchy nature of the habitat, abiotic habitat differences such as soil mineral content, and restricted gene flow because of low mobility.
No site-specific crustacean inventories have been published on this region. However, locality data embedded in the scientific literature, recent agency reports, and communications with experts who have collected here reveal records of at least 17 species of branchiopod crustacean within our study area. An additional 31 species are known from other parts of New Mexico, Arizona, and/or Mexico. Note that Cladocerans in ephemeral pools have received much less attention than fairy shrimp, tadpole shrimp, or clam shrimp, and are therefore discussed here only in passing.
Patterns of branchiopod distribution in the Peloncillo region can be complex and seem to be affected by temperatures, pool form, and salinity and other soil characteristics. Winter rains often bring out a different fauna from summer rains. In the Lordsburg Playas, for example, the winter fauna is dominated by Brachinecta mackini, Lepidus lemmoni, and Cysticus mexicanus. Summer composition switches to predominantly Thamnocephalus platyuris, Streptocephalus n. sp. 1, and Leptestheria setosa. Different habitats tend to harbor different species. Many species show up in stock tanks and other man-made impoundments; the stock tank fauna overlaps quite a bit with species found in natural tinajas. Species in the large playas, however, tend not to show up in tinajas or stock tanks—unless these stock tanks are built into playa soils. One undescribed species (Streptocephalus n. sp. 1) has been found only in the large playas. A second (Streptocephalus n. sp. 2) has been found in small pools at playa edges and away from playas.
Across the West, branchiopods tend to be segregated by elevation, yet so far the Sky Island faunas look to be very similar from valleys to peaks. Because branchiopods are so opportunistic, however, further studies are likely to find exceptions to many of these trends.
Numerous studies on genetics, natural history, and evolution of branchiopods use pools in the San Simon Valley near Portal, Arizona, as the source of several branchiopod species. These species include Triops longicaudatus and Triops newberryi , Eulimnadia texana, and Eulimnadia diversa. These studies have brought insights into themes as broad as how animals can survive in such extreme environments115, how habitat differences affect life history traits, how populations can maintain harmful genes at a high frequency, and how males and hermaphrodites can coexist in the same population through time. Further studies of Triops species in the U.S. and Mexico have revealed complex genetic differentiation and cast doubt on current species limits. For example, T. newberryi may not be a valid species, and T. longicaudata probably includes more than 15 cryptic species across its range. T. longicaudata also comes in several forms that are reproductively isolated from one another by sexual system; a single pool can harbor a sexual form with “normal” males and females, a parthenogenic form, an androdioecious form in which males cannot contribute to the next generation (being functionally sterile products of genetic accidents), and other strange forms.
Special management concerns: Chemical alteration of playa systems has occurred in other parts of the region (e.g., dumping of oil wastes in southeastern New Mexico and polluted irrigation wastewater in Texas and Kansas). This type of use would likely be very harmful to playa invertebrates here as well, although more inventory and monitoring would be required to assess precisely what species would be affected how. Effects of chemical poisons such as Rotenone (used for eradicating non-native aquatic vertebrates) or chemical brush-control agents should also be investigated before being applied on a large scale or in pools that may harbor rare species. Because ephemeral pools fill with runoff, chemicals applied on surrounding lands do make their way into pools and can concentrate there.
Many ephemeral pools are kept open and habitable to branchiopods by disturbance of one sort or another. Disturbance should therefore not be viewed as necessarily detrimental, although effects of specific disturbances on rare species should be evaluated on a case-by-case basis. There is no evidence, for example, that grazing harms most branchiopod species in this region. Man-made stock ponds provide excellent habitat for some branchiopod species. It is not clear where these species would have occurred naturally, although many stock ponds simply impound extra water in sites that accumulated ephemeral pools before impoundment. When stock tanks need to be dug out or recontoured, some branchiopod researchers recommend that the top few centimeters of soil (which contain most of the branchiopod cysts) be removed first, set aside, and replaced after recontouring is complete. Drying of stock ponds to eradicate non-native fishes and frogs will not harm branchiopods.
Branchiopod researchers have suggested that “ . . . conservation efforts for playa invertebrates should be implemented on the landscape-level and focus on playas with intact watersheds, because these playas have relatively undisturbed hydroperiods.” The playas in this focal area fit this bill exceptionally well.
Some habitat managers have experimented with “moist soil management,” keeping temporary wetlands wet for longer periods of the year in order to benefit waterfowl and other wildlife. Moist soil management can increase the densities of wetland arthropods. However, the effects of altering hydrologic cycles in this way on branchiopod abundance, diversity, and genetic population structuring are not clear. Any proposed hydrologic alterations should be viewed as potentially disruptive, and scrutinized in detail.
Other Crustaceans
Amphipods: There are no published records of amphipods in this area, but they are almost certain to exist in at least some springs and cienegas. Hyalella azteca is common throughout North American wetlands. Other sites in the Southwestern US and Northwestern Mexico have endemic isopods in the genus Gammara, including several species in the Gammarrus pecos species complex throughout the northern Chihuahuan Desert. Wetlands should be examined for presence of amphipods. It may take genetic analysis to determine correct species and population placement of some specimens encountered. One non-native, Gammarus lacustris, is reportedly introduced into Arizona, but may only occur at higher elevations. Thus far nothing published has been found on the effects this species might have on natives.
Isopods: Two species of terrestrial isopods (Armadillidium vulgare and Venezillo arizonicus), commonly known as pill bugs or rolly-pollies, are known from the Chiricahua Mountains. Both are likely also present in the Peloncillo region.
Crayfish: There are no native crayfish in this part of Western North America, but a species from eastern North America (Oronectes virilis) has invaded some streams in the region and causes problems for native fish, amphibians, and aquatic plants where it occurs.127 Care should be taken to avoid introducing this invasive species into permanent wetlands in the focal area. Luckily, this species does not persist in ephemeral waters.
Knowledge Gaps
There are two main ways to increase our knowledge of the area’s invertebrate fauna. The first is to conduct and/or facilitate new inventory projects. The second is to compile existing information into a useable format.
New inventory efforts can be done in intensive or diffuse ways depending on available resources and project goals. An intensive inventory would involve bringing in experts on numerous taxonomic groups along with their sampling teams, setting up high-throughput specimen processing systems, and running all information immediately into a centralized database. This would collect a large amount of baseline data in a short amount of time. Similar rapid assessment inventories have been successful in many places across the globe, and experience from these ventures has led to development of many efficient techniques for specimen and data management. Longer-term, more thorough versions of such inventories are also being undertaken, with the goal of fully documenting the extraordinary richness of invertebrate faunas (or at least getting far enough to produce reliable estimates of total richness).
Diffuse inventories take advantage of work already going on in the region, can be done on a smaller scale, and can more practically be continued or repeated over time. The main expenses of this strategy would be defraying field costs for interested parties and providing an assistant to compile information into a database as it comes in. Small grants ($500 - $3,000) are often enough to cover fieldwork expenses for individual groups (e.g., a team of 3 - 4 experts spending one to two weeks inventorying dragonflies and damselflies in all the springs and streams throughout the planning area). Fieldwork here could be piggy-backed on other research projects, (e.g., invertebrate taxonomy courses run at the SWRS). For example, at the end of the annual week-long bee taxonomy course, students and researchers could be brought into this planning area for an additional three workshop days, likely for the cost of providing them with room and board. The existing butterfly-watching tours of Guadalupe Canyon could be turned into meaningful inventory sessions by providing these experts with a data-recording assistant.
Cooperation by agencies and private landowners will be key to encouraging these diffuse inventory efforts. The detailed area descriptions present in this plan and its appendices will greatly improve the efficiency and effectiveness of future inventory work of all sorts by helping researchers sample the breadth of the habitats present and target the sites likely to harbor the richest assemblages of their particular group. Another possibility would be to start a long-term volunteer count associated with the North American Butterfly Association (NMBA) 4th of July Butterfly Counts; New Mexico’s Organ Mountain Count now has about 13 years of data which is helpful in tracking butterfly populations as well as species found in a given area.
Much more collecting has been done in the area than has been documented in any formal way. For over 100 years, the Sky Island region had drawn entomologists with the lure of exotic finds. The American Museum of Natural History’s Southwestern Research Station, just nine miles from the greater Peloncillo region, was originally founded for its tremendous insect diversity and has attracted hundreds of invertebrate researchers over the last 50 years. Many of these researchers will have collected in the nearby valleys and ranges, but information from these collections has never been compiled.
Compiling results of these informal collections would represent a huge advance in the knowledge of the area’s invert fauna. The centipede Theatops posticus, for example, was thought for many decades to be rare in the Southwestern US, known from just one locality in Utah and one in Arizona. But when an expert examined collections in several museums, he found specimens of T. posticus (previously unidentified) from nearly 100 sites across the southwestern U.S. and northern Mexico, including the Peloncillo Mountains.
Specimens in existing collections also represent a long time scale, some exceeding 150 years in this borderland area. These collections may include species that no longer exist in their original localities, or ones that occur there only periodically. This information can help identify habitat changes and potentials. If, for example, old collections include a caddisfly that lives only in permanent running streams, this may indicate that a now-ephemeral stream once ran year-round and might do so again with restoration work.
Compiling knowledge from existing collections would require contacting a large number of entomologist and amateur collectors, recording and standardizing collection data from each, and making sense of these data. Because many invertebrate groups are very difficult to identify accurately, data quality will vary from collector to collector and from taxon to taxon. Having one expert in each group review and verify identification of specimens would improve the reliability of these data immensely, though it could be time consuming and expensive. To be practical, compiling existing knowledge would require hiring someone to coordinate the outreach process and to manage the resulting database. Because most invertebrate museum collections are not yet digitized, the coordinator would likely also have to travel to major collections to extract data from collection labels directly. Most professional entomologists are already busy with their existing projects, so providing someone to facilitate their compiling of their information would likely make the difference between having project participants limited to a few retirees and having a large set of collaborators that includes many active researchers.
Public recognition of the value of an area, this report being an excellent example, facilitates increase in knowledge of poorly studied groups in several ways. First, it calls researchers’ attention to an area they might otherwise overlook. Second, it focuses funders’ attention on the same area, and greatly improves the chances that a researcher who wants to work in the area can get funds to do so. Third, for people have already done work in the area, public recognition adds a level of prestige to this work that causes completion and publication of this work to rise on people’s priority lists.
Conservation Targets
Quite a few species are endemic, or nearly endemic, to the Peloncillo region. These should all be considered conservation targets, if only to prevent accidental, avoidable damage to their survival. Riparian areas are critically important to many invertebrates and disproportionately valuable to many more. This includes riparian bosques as well as the watercourses themselves.
Playas host huge numbers of species when they fill with water. Many of these species are not found outside of these playa areas, or would not survive without access to them. Isolated springs host at least one and possibly more endemic species. They are a valuable resource to non-endemics as well. Other watersources, including man-made pools, also provide valuable resources for any invertebrates.
Patches of unusual soil types can also be considered conservation targets because of the high diversity of ground-nesting invertebrates known from the region. Not all of them have been identified, although the patch of stabilized dune in the Animas Valley has been suggested as one such type.
Overall, maintaining natural disturbance regimes, including fire, is likely to benefit some invertebrates directly. By supporting continued high plant diversity and natural hydrologic flows, these processes benefit even more invertebrates indirectly.
General landscape protections established for wide-ranging “umbrella species” such as jaguars or wolves will preserve habitats needed by most invertebrates. However, some species with very small ranges or very specific habitat requirements may need additional targeted management.
Endemic talus snails or springsnails, for example, may live on just one hillside or in one isolated cienega. Negative impacts to such small areas can usually be avoided easily—if the need to do so is recognized. On the flip side of the coin, protection or restoration of an area too small to sustain larger animals may be very valuable to invertebrates.
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Section Authors:
INVERTEBRATES - Gitanjali Bodner, Ph.D. Biologist and Conservation Planner, Sky Island Alliance. Trained in systematics and biodiversity assessment of hyperdiverse invertebrate groups, Gita applies a range of research approaches to compiling place-based knowledge and filling data gaps.
