Abstracts

Thirty-Second Annual Meeting of the American Arachnological Society

Hosted by:

Rosemary Gillespie & Charles Griswold

Final Version June 17, 2008

at the

The University of California at Berkeley

Spider silk as a novel humidity-driven biomimetic muscle

Department of Biology
Integrated Bioscience Program
University of Akron
Akron, Ohio USA

Ali Dhinojwala

Department of Polymer Science
Integrated Bioscience Program
University of Akron
Akron, Ohio USA

Abstract: The abrupt halt of a bumble bee’s flight when it impacts the almost invisible threads of an orb web provides an elegant example of spider silk’s amazing strength and toughness.  Spiders depend upon these properties for survival, yet silk’s impressive performance isn’t limited solely to tensile mechanics. For instance, spider dragline silk ‘supercontracts’ in high humidity. During supercontraction, unrestrained dragline silk contracts up to 50% of its original length while restrained fibers generate substantial stress. Here we discuss novel findings which demonstrate that dragline silk exhibits two qualitatively different responses to humidity. We show that supercontraction is a permanent, rate dependent, tensioning of restrained silk in response to high humidity, and that post-supercontracted silk differs in some mechnical properties from virgin silk. However, silk also undergoes a previously unknown cyclic relaxation-contraction response to wetting and drying, which involves cyclic intake and loss of water. These powerful cyclic contractions give silk the potential to act as a high performance, water-controlled, mimic of biological muscles, repeatedly generating work 50x greater than that of human muscle. Silk may emerge as a new and powerful model for biomimetic muscle with possibilities in designing light weight and compact actuators for various applications.  posted 2 June 2008

Revision of the genus Padilla Peckham and Peckham, 1894 (Araneae - Salticidae) — convergent evolution of secondary sexual characters due to sexual selection and rates of molecular evolution in jumping spiders

Daniela Andriamalala

Department of Biological Sciences
The George Washington University
Washington DC 20052, USA.
Email: dand@gwu.edu

Abstract: The horned jumping spider genus Padilla restricted to Madagascar is revised. The genus comprises 15 species, which are diagnosed, described, and illustrated in detail. Three synapomorphies of the genus are proposed. Twelve species are new. A phylogenetic analysis of 38 morphological characters and two genes (COI and 28S) exhibit a conflict between the morphological and molecular hypotheses due to convergent evolution of the secondary sex traits such as horn shape, which appears to be due to sexual selection. The monophyly of the genus was confirmed both by the Ballinae morphological analysis (Benjamin, 2004) and the Salticidae 28S analysis (Hedin and Maddison, 2003). Within Ballinae, Padilla is the sister group of Phylates. Within Salticidae, Padilla is the sister group of two balline genera: Pachyballus and Ballus with which it forms a monophyletic group that is sister group to a clade including marpissoids, heliophanines, freyines, euophryines and plexipoids. Penalized likelihood was used to assess the average rates of molecular evolution of the 28S gene and the ages of the genus and members of the family Salticidae for the first time. Padilla diverged from the other ballines around 13.06Mya and the Ballinae sub-family from other salticids around 23.17Mya. Those ages are too recent for Gondwanan vicariance hypotheses, the “stepping stone” hypotheses offers a better explanation. posted 28 May 2008

Phylogenetic relationships of the spider family Tetragnathidae (Araneae) based on morphological and DNA sequence data

Department of Entomology
California Academy of Sciences
San Francisco, CA USA

Gustavo Hormiga

Department of Biological Sciences
The George Washington University
Washington DC, USA

Abstract: The limits, phylogenetic relationships and placement of tetragnathid spiders have been controversial for more than a century. Classifications prior to numerical phylogenetic analyses either recognized Tetragnathidae as a separate family, as a lineage of Araneidae, or placed some of its members in both families. There are three central problems regarding the higher level systematics of tetragnathids: the placement of Tetragnathidae in Araneoidea, the exact limits of the family and the monophyly and phylogenetic relationships of the various tetragnathid groups. Despite recent advances, some of these questions remain unsatisfactorily answered and robust cladistic support for several of these groups remains elusive.  We have collected morphological, behavioral and DNA sequence data with the main goal of addressing the last two questions.  To a lesser extent, our data also are relevant to the first question, since these three problems are hierarchically linked.  In this presentation we will discuss our progress in the combined analysis of these data. Our morphological and behavioral phylogenetic analysis includes 48 terminal taxa scored for a total of 213 characters.  In addition, we collected an approximate total of 6300 nucleotides positions form the 12S, 16S, 18S and 28S ribosomal subunits and for the protein coding genes cytochrome c oxidase subunit I and histone H3. We analyzed these data with dynamic and static homology criteria and we explored clade sensitivity to different data partitions. We also studied the sensitivity of the resulting clades to different phylogenetic inference methods (parsimony and Bayesian phylogenetics) and quantified clade support. posted 7 June 2008

Evolution of male genitalia in the trapdoor spider genus Myrmekiaphila (Araneae: Mygalomorphae: Cyrtaucheniidae: Euctenizinae)

Ashley L. Bailey

Department of Biology
East Carolina University
Greenville, N.C. USA

Abstract: The euctenizine trapdoor spider genus Myrmekiaphila comprises 11 species and is widely distributed throughout the southeastern United States.  This group is probably best known for their interesting burrow architecture – they are the only mygalomorph spiders in North America that conceal their subterranean side chambers with a secondary trapdoor.  These spiders were recently revised and placed into three informal species groups based upon differences in male genitalia, but a phylogenetic hypothesis has never been performed to assess monophyly of these groups.  We present the first phylogeny for Myrmekiaphila based on DNA sequence data obtained from three mitochondrial and nuclear gene loci (12S, 16S, and 28S).  We use this phylogeny as the evolutionary framework to examine the monophyly of these species groups, to test hypothesized species boundaries, and to comment on the evolution of male genitalia.  Our phylogeny demonstrates that species groups (and some species) are paraphyletic, and results from ancestral character state reconstruction analyses show that the distinct forms of genitalia – particularly the absence of a secondary prong – have evolved in parallel (i.e., they do not form clades).  These data suggest that characters ordinarily given heavy weight for delineating taxa in Myrmekiaphila need to be reconsidered and interpreted in light of this new phylogenetic evidence. posted 6 June 2008

Reevaluation of the canonical model of spider gastrulation

Department of Biology
Reed College
Portland, Oregon USA

Crystal Chaw

Department of Integrative Biology
U. C. Berkeley
Berkeley, California USA

Abstract: Gastrulation is a physical process in embryonic development that converts the simple polarities of the egg into the more complex organization of the later embryo.  The main body axes arise during gastrulation as a consequence of the organized movements of cells into the interior. The historical literature on spider development reports that gastrulation occurs in one continuous phase with two cell types involved.  First, cells internalize at a central blastopore to form the primitive plate, an early two-layered region.  Then a group of these deep cells, the cumulus, detaches and migrates to the edge of the germ disc; the direction of migration determines the dorsal-ventral axis.  We have studied gastrulation in four species using high-resolution video microscopy and improved histology.  We find that only Cheiracanthium mildei develops according to the model.  In contrast, gastrulation in Zygiella x-notata and Latrodectus mactans involves precocious internalization of cumulus cells.  In Z. x-notata additional cells internalize at a novel structure called the caudal bud.  Primitive plate formation in Loxosceles laeta is preceded by widespread internalization of a unique population of cells we call cell islands; their fate is unknown. posted 28 May 2008

Phylogenetic placement of the jumping spiders (Salticidae) of Gabon-  implications for biogeographic patterns in body forms

Melissa R. Bodner

Department of Zoology
University of British Columbia
Vancouver, British Columbia CANADA

Abstract: Jumping spiders (Salticidae) constitute the most species rich family of spiders, with 5000 known species worldwide. Prior to this study, molecular phylogenetic sampling has emphasized New World taxa with some inclusion of groups from Australasia. Little work has been done to understand the diversity from tropical forests in Africa.  Here we present a phylogenetic tree with expanded sampling and discuss the evolutionary placement of species from Gabonese tropical forests. We also present a novel primer set for amplifying Actin 5C, a nuclear gene that may prove useful for spider phylogeny.
  Analyses based on 28S, Actin 5C, CO1 and 16SND1 data suggest there is a previously unrecognized, independent radiation of jumping spiders unique to Central Africa.  Our findings are concordant with previous studies that suggest that many large salticid clades are endemic to a continental region, or nearly so. Isolated radiations on different continents show a similar spectrum of body forms, which may reflect a corresponding diversity of ecological niches occupied. This suggests that body form convergence is widespread in Salticidae and that whole, independently evolving communities may be converging in ecomorphological make-up. posted 7 June 2008

Taxonomy and phylogeny of the Tegenaria-Malthonica complex (Araneae, Agelenidae) using morphological and molecular data – preliminary results

Angelo Bolzern

Naturhistorisches Museum Basel
Department Life Sciences, Basel, SWITZERLAND

Naturhistorisches Museum Basel
Department Life Sciences, Basel, SWITZERLAND

Abstract: Malthonica Simon and Tegenaria Latreille represent two species-rich genera of the family Agelenidae. They are predominantly Palaearctic in distribution. Currently 41 species and one subspecies are described in Malthonica and 101 species in Tegenaria, respectively. The group is notorious for its taxonomic problems: lack of diagnoses of the two genera, arbitrary generic assignment of species, availability of information for only one sex in many species, unknown internal phylogenetic relationships and presence in collections of additional undescribed species. Recently, several Tegenaria species were transferred to Malthonica, based on the embolus length, a character which is on its own not sufficient for phylogenetic reconstructions. An additional problem: Tegenaria agrestis, a species native to Europe and introduced into the USA, where it is blamed for biting humans and causing serious wounds followed by necrosis. In Europe, no such case is known. The question of conspecifity of the American and European populations can be answered as a by-product of the revision of the European Tegenaria-Malthonica complex. The phylogenetic relationships within the complex will be analysed using morphological and molecular methods. The following aspects are presented: 1) potentially useful morphological characters for delimiting the genera, 2) some taxonomical results and 3) preliminary molecular analyses. posted 30 April 2008

Quality not quantity: Sperm viability not number determines male fertility in the harlequin beetle riding pseudoscorpion

Melvin M. Bonilla

Department of Biology
Program in Ecology, Evolution and Conservation Biology
University of Nevada, Reno
Reno, NV USA

Abstract: Despite decades of research since G.A. Parker's seminal papers on sperm competition, the factors responsible for variation in sperm competitive ability remain poorly understood. While numerous investigations have focused on total number of sperm per ejaculate, our findings on the harlequin beetle riding pseudoscorpion, Cordylochernes scorpioides, suggest that sperm viability may be the most important factor contributing to variation in male fertilization success. Because C. scorpioides males transfer easily quantified sperm in discrete packets, this pseudoscorpion provides a model system for determining the impact of ejaculate characteristics on male fitness. In a study employing live/dead fluorescent staining of sperm, we assessed sperm number and proportion of viable sperm in the first two spermatophores produced by 140 males. This study revealed that proportion of viable sperm is more variable between males and more repeatable within males than total sperm number. The two traits are, in fact, significantly negatively correlated, suggesting a trade-off between number and quality of sperm. Moreover, selection gradient analysis indicates that proportion of viable sperm is a better predictor of male fertility than either total sperm number or the total number of viable sperm. Given the importance of sperm viability to male fertility, the extreme variability in this character (coefficient of variation of 87%) seems paradoxical. Constraints on the capacity of selection to hone maternally-inherited mitochondria for sperm function may provide at least a partial resolution of this paradox. Preliminary data indicating high variation in proportion of viable sperm across C. scorpioides matrilines are consistent with this hypothesis. posted 6 June 2008

Effects of temperature on activity and movement in a web-building spider (Araneidae)

Lisa Borowski

Department of Biology
Eastern Michigan University
Ypsilanti, Michigan U.S.A

Abstract: As ectotherms, spiders obtain their heat from the external environment and rates of activity are strongly influenced by temperatures differences.   Thermoregulation includes movement to specific areas where temperatures match an organism’s preferred body temperatures allowing for optimal efficiency and activity.  We compared movement of web-building spiders (Araneidae) maintained at two different temperatures; 12°C and 20°C.  Animals in the 12 °C environmental chambers were provided with temperature gradient using a heating pad placed at one end of the arena.  Arenas from both groups were rotated 180° after two weeks.  Observations and measurements were taken three times a day for four weeks to record daily movement and activities.  We hypothesized that spiders in the 12°C environmental chambers would be less active than the spiders in the 20°C environmental chambers and would return to the warm area for their daytime refuge.   Initially, there was no significant difference in movement between the two groups, however, after the arenas were rotated, the 12 °C group was more active.  In addition, the majority of spiders maintained their original retreat site regardless of the temperature gradient. posted 5 June 2008

Mechanical and material properties of silk from Achaearanea tepidariorum (Araneae: Theridiidae) differ within the web

Cecilia Boutry

Department of Biology and Program in Integrated Bioscience
University of Akron
Akron, Ohio USA

Abstract: Spiders have up to seven different silk glands that yield different types of silk with distinct composition and properties. Moreover, the same type of silk can be used for many different functions. Major ampullate silk is used in web construction, as a safety line and as a way for spiders to mark their path. In Theridiidae, major ampullate silk is used to spin different components of the cobweb. The cobweb of the theridiid Achaearanea tepidariorum includes two components: a network of supporting threads and a series of vertical sticky gumfooted threads directly involved in prey capture. These two components function differently in ways that may require distinct material properties. Supporting threads were thicker and able to bear higher loads before breaking and before deforming permanently compared to sticky gumfooted threads. This could be needed to support spiders and prey. In contrast, sticky gumfooted threads were stretchier and tougher, which allowed them to better absorb kinetic energy during prey capture. Thus, threads formed of the same silk, despite having the same composition, can present different material properties depending on the conditions under which they are spun. posted 7 June 2008

Has passive re-colonization successfully replaced the spider assemblage on a restored tall grass prairie in Ohio?

Department of Evolution, Ecology and Organismal Biology
The Ohio State University
Marion, Ohio, USA

Shauna Price

Department of Ecology and Evolutionary Biology
University of California at Los Angeles
Los Angeles, California, USA

Abstract: The reconstructed prairie on the campus of the Marion Campus of Ohio State University has been in existence since 1977.  Restoration efforts have focused on plants.  The animals present on the site have re-colonized without active management.  Spider assemblages were sampled after 23 years at this restored prairie and compared to those sampled on two remnant prairies, and two old fields.  Sampling methods included pitfall traps and sweeps.  A total of 1,541 identifiable spiders representing 94 species were captured, about 91% of these with the pitfall traps. There is some evidence that the restored Marion Campus Prairie is inhabited by an assemblage of spiders resembling those present on remnant prairies. posted 19 May 2008

Association of spider abundance with El Nino events: 15 years of data from 3 elevations in the Jemez Mountains, New Mexico

Sandra L. Brantley

Museum of Southwestern Biology
University of New Mexico
Albuquerque, New Mexico USA

Abstract: The El Nino weather pattern strongly affects precipitation in the southwestern US, generally producing more precipitation than average (El Nino) or less precipitation than average (La Nina) from October to May. In the Jemez Mountains of north-central New Mexico I use pitfall traps to monitor ground-dwelling arthropods at three elevation zones: pinon-juniper woodland (1948 m), ponderosa pine forest (2454 m), and mixed conifer forest (2717 m), and ask how the fauna in each zone are affected by these events. Here I report on richness and abundance data for 7 families of spiders from 1993-2007. Results showed that single wet or dry years did not produce significant changes in spider abundance, but a series of wet or dry years had a strong impact. The mostly dry years 1995-1997 and 1999-2004 greatly reduced abundance at all sites, with the pinon-juniper habitat affected most strongly. Abundance during the wet years 1991-1994 and 2005-2007 was more variable across taxa and elevation zone. Cluster analysis based on spider abundance showed that dry years clustered together, but the two extended wet periods did not. Species tended to remain in their elevations zones rather than move during the extended wet or dry periods. Dominant species remained dominant throughout the 15 years, while rarer species reached very low numbers or were not collected at all during dry years. posted 2 June 2008

Little things mean a lot: proposed project for Linyphiidae of the arid southwestern United States

Museum of Southwestern Biology
University of New Mexico
Albuquerque, New Mexico USA

Department of Natural and Applied Science
University of Wisconsin
Green Bay, Wisconsin USA

Department of Entomology, Plant Pathology and Weed Science
New Mexico State University
Las Cruces, New Mexico USA

Linda F. Wiener

St. John’s College
Santa Fe, New Mexico USA

Abstract: Linyphiids are strongly associated with mesic habitats; in the Western Hemisphere they are actively studied in Canada and the northern US, and Central and South America. However, linyphiids also occur in the arid southwestern US but are not well studied, although the region represents great variation in topography, including high elevations, isolated mountains, isolated springs and wetlands, river corridors, and grasslands. We plan to survey linyphiids from Arizona, New Mexico, and West Texas, building on the records from Richman et al. (114 taxa), adding specimens from our own collections and regional museums, and collecting fresh specimens that can be preserved for morphological or molecular research techniques. From this work we can better address ecological questions, including distribution patterns of species on isolated mountains and microhabitats, and along river corridors. We expect to discover new species and range extensions for some known species; our inventory will also form a base list of species expected from northern Mexico, whose desert systems also contain mountain and basin habitats. The list will serve as a partial foundation for future more geographically inclusive taxonomic revisions. New species and distribution information will be reported in the Richman et al. checklist and the Nearctic Spider Database. We will deposit material in our regional museums (the University of New Mexico houses type specimens and frozen tissues), where it will be available for systematics or ecological researchers. posted 2 June 2008

The maritime life of Peruvian coastal solifuges

Integrative Biology
University of California Berkeley
Berkeley, CA USA

Department of Zoology
Denver Museum of Nature and Science
Denver, CO USA

Paula E. Cushing

Abstract: The coastal Peruvian desert is one of the driest ecosystems in the world, much of it appearing as barren land devoid of vegetation. Despite its scant primary productivity, this moonscape is inhabited by an abundant arachnid fauna, including large populations of seabird ticks, terrestrial pseudoscorpions, spiders, scorpions and solifuges. How can these animals succeed in such harsh environment? Here we present data supporting the hypothesis that marine productivity is subsidizing populations of two species of solifuges, Chinchippus peruvianus and a new Chinchippus sp. from Isla La Vieja, Paracas National Reserve. In the first species, individuals feed on intertidal crustaceans, and reach densities of up to 6 solifuges/sq m (mean 1.19 ± 0.14 solifuges/sq) m in the intertidal zone. The number of solifuges decreases with distance from shore. At La Vieja, Chinchippus sp. was found in seabird colonies, and likely feed on seabird ectoparasites and arthropod scavengers. Carbon and nitrogen stable isotope analysis indicates the marine source of energy and nutrients for these solifuges. An analysis of stomach contents of one predator of both species, the gecko Phyllodactylus angustidigitus, suggests that solifuges are more frequent in insular habitats and the desert adjacent to bays than they are in the desert away from shore or along the cliff-bound shoreline. This study shows how solifuges, by extending their niche to intertidal and insular habitats, can successfully colonize a hyper-arid coastal desert. posted 28 May 2008

Microhabitat types influence soil mite diversity in Northwest forests

Department of Biology
Lewis and Clark College
Portland, Oregon USA

Andrew Moldenke

Deptartment of Botany & Plant Pathology
Oregon State University
Corvallis, Oregon USA

Abstract: Acari are an extraordinarily diverse order of arachnid, and the most abundant taxon of soil arthropods. Although Acari make up a significant portion of the soil food web, we know little about their abundance, diversity, and factors that influence their micro-distribution. Because Acari are so abundant and are environmentally sensitive, they can be used as indicators of the greater soil arthropod community.  Our goal was to compare soil mite diversity between soils with different nitrogen inputs. Alnus rubra (Red Alder) has a symbiosis with Frankia, an actinomycete that forms nitrogen-fixing nodules on the tree’s roots.  A significant portion of this nitrogen is directly incorporated into A. rubra’s biomass, and the decomposition of its tissues causes soil in A. rubra stands to be rich in nitrogen. If an increase in nitrogen in A. rubra soils significantly affects soil arthropod communities, one would expect to see a difference between mite communities present in A. rubra stands and those present in other forests. In this study, we compared the composition and structure of mite communities in two forest types; A. rubra stands and Acer macrophyllum stands.  We found that mean Shannon-Weiner diversity index values were higher in A. rubra stands, though variation in the A. macrophyllum stands made the difference statistically insignificant.  An analysis of similarity (ANOSIM) showed that mite communities are distinct between two A. rubra and two A. macrophyllum stands. These findings suggest that nitrogen inputs to soil by A. rubra in the form of litter create differences in soil microarthropod communities. posted 3 June 2008

Are Pardosa sierra Banks, 1898 epigynia morphs belong to the same species?

Francisco J. García de León

Conservation Genetics Laboratory
Centro de Investigaciones Biológicas del Noroeste
La Paz, B.C.S., MEXICO

Abstract: Pardosa sierra was described by Banks in 1898 from Sierra de la Laguna (epyginum morph A herein) and Barnes (1959) made a revision of the lapidicina species group of Pardosa, where he illustrated another epigynum morph (B) from Sierra City, California. It is not clear if these two morphs are the same species. This uncertainty is due the distribution of the morphs is not complete known. In this study we collected morph (A) in nine oases of Baja California Sur and morph (B) in Chihuahua. A preliminary genetic distance (Kimura 2-parameter) analysis of the sequence fragment COI mDNA from each morph and other species of lapidicina and milvina groups, along with seven sequences of Pardosa from the Gen Bank, was conducted. This analysis reveled grater genetic distances between haplotypes of P. sierra morphs (genetic distance GD = 0.057) than other species of the lapidicina group. Moreover, morph (A) was closest to P. vadosa (GD = 0.055), and morph (B) was closest to P. steva (GD = 0.031). Overall, morphological and genetic differences and disjunct distribution suggest that P. sierra morphs might be different species so far. Further collect efforts are needed to support this hypothesis. posted 7 June 2008 and revised 10 June 2008

Patterns of evolution in Caribbean Selenops

Sarah C. Crews

ESPM – Organisms and Environment
University of California, Berkeley
Berkeley, CA USA

Abstract: In the Caribbean, biodiversity has been shaped by fragmentation of islands from larger landmasses coupled with intermittent submergence, as well as formation of new land in the form of volcanic islands. Thus, the relationship between vicariance, dispersal, and in situ evolution in shaping island biota has long been a subject of debate. Although general patterns can be detected within lineages, there are fewer between lineages, and biogeography is often treated on a taxon by taxon basis. Only once the basis for the differences between disparate taxa are understood will we be able to make generalities in terms of underlying mechanisms of diversification, allowing greater insights into evolution, ecology and speciation on islands. The current study focuses on the genus Selenops (Selenopidae), which is extremely diverse in the Caribbean region. We use molecular (multi-gene sequence data) and morphological data from a broad geographic sample to examine whether observed patterns of evolution mirror those of geology. In general, colonization is limited and subsequent diversification is dictated by island age, size and isolation. Specific patterns revealed thus far include 1) Species from southern Caribbean islands generally cluster outside other Caribbean species; 2) Selenops in the southern Lesser Antilles are distantly related to those in the northern Lesser Antilles, a pattern mirroring that of similarly diverse Anolis lizards; 3) Islands with a greater diversity of habitat types and surface area have more species than smaller islands. posted 6 June 2008

Vampire spiders: the advantage of being smelly

School of Biological Sciences
University of Canterbury
Christchurch, NEW ZEALAND

Simon D Pollard

Canterbury Museum
Rolleston Avenue
Christchurch, NEW ZEALAND

Abstract: Jumping spiders (Salticidae) have unique, complex eyes, and vision based on spatial acuity that is unrivalled by other animals in their size range. They also have elaborate vision-based predatory strategies and often spectacular vision-based courtship displays. However, chemical cues are also known to play important roles in these spiders’ predatory and mating strategies. Evarcha culicivora is a salticid from the Lake Victoria region of East Africa. This is a spider that indirectly feeds on vertebrate blood by actively choosing as prey female mosquitoes that have had recent blood meals, and this unusual diet appears to be driven in part by sexual selection. Males and females of this species are both active in courtship, both have distinctive mate-choice behaviour and both appear to use blood as perfume. By feeding on blood-filled mosquitoes, E. culicivora males acquire an odour that makes them more attractive to conspecific females and E. culicivora females acquire an odour that makes them more attractive to conspecific males. posted 5 June 2008

Structure of papillae on the pedipalps of solifuges -- revisited

Lorenzo Prendini

Division of Invertebrate Zoology
American Museum of Natural History
New York, NY USA

Abstract: Some male solifugids in the families Eremobatidae, Karshiidae and Solpugidae (Arachnida, Solifugae) have clusters of conical to hairlike projections on the ventral surface of the metatarsus of the palpal papillae. Previous work indicated that the ultrastructure of the papillae were consistent within families but varied between families. We present microstructural evidence from histogical examination (Transmission Electron Microscopy) that these papillae function as contact chemoreceptors and may be involved in perceiving chemical signals released by females. posted 5 June 2008

Colorado Spider Survey and Denver Museum of Nature & Science arachnology collection – ten years later

Paula E. Cushing

Department of Zoology
Denver Museum of Nature & Science
Denver, CO USA

Abstract: The arachnid collection at the Denver Museum of Nature & Science (DMNS) was established in 1998 and the Colorado Spider Survey (CSS) was initiated the next year. Here we present a summary of the holdings of this relatively young collection, an update on the findings of the CSS, publications and presentations that have resulted from the collection and the project. We also present information on the effective citizen science aspects of this project including the number of people trained, the number of volunteers that have remained active with the project, and some of the programs and projects these volunteers have spearheaded. posted 7 June 2008

Systematics and evolution of the Sclerobuninae (Opiliones, Travunioidea)

Shahan Derkarabetian

Department of Biology
San Diego State University
San Diego, California USA

Abstract: The subfamily Sclerobuninae is a group of laniatorean opilions found in western North America, currently classified into the genera Zuma, Sclerobunus, and Cyptobunus. Sclerobunus species are typically found in forested habitats, and range from Arizona north into Idaho and west to Washington and Oregon. Described Cyptobunus taxa are restricted to cave habitats in Montana, Nevada, and Utah. Currently these genera are hypothesized to be sister genera. Using CO1 mtDNA and 28S nuclear DNA, we present a phylogenetic analysis of all sclerobunines. The genus Zuma is not obviously a sclerobunine, and neither Cyptobunus nor Sclerobunus are recovered as monophyletic.  Within Sclerobunus, S. r. robustus is split into 5 genetically distinct, geographically concordant clades, which may represent cryptic species. Sclerobunus r. idahoensis is found to be more closely related to S. nondimorphicus than to S. robustus. Specimens morphologically identified as Cyptobunus are nested within Sclerobunus, with at least three independent origins suggesting repeated convergence to a cave-dependent morphology. Of particular interest are Cyptobunus specimens found near Taos, New Mexico. These particular Cyptobunus specimens were found deep in a rockpile, and are genetically closely-related to a syntopic population of S. r. glorietus. This suggests a recent, local transition to a “troglobitic” morphology in a non-cave environment.posted 30 May 2008

A new genus of tetragnathid spiders from Australia with an expanded phylogenetic hypothesis for the generic relationships of Tetragnathidae

Department of Biological Sciences
The George Washington University
Washington, DC, USA

Gustavo Hormiga

Abstract: We present a newly discovered genus of tetragnathid spiders from Western Australia and discuss its phylogenetic placement using comparative data for a wide range of tetragnathids and outgroup taxa. The new genus is highly autapomorphic and has an unusual mixture of morphological characters, both genitalic and somatic. The phylogenetic study is based on a combination of morphological and molecular characters. We have also studied and sequenced several tetragnathid taxa whose phylogenetic position has been very poorly understood. The data have been analyzed using parsimony (both under direct optimization and static homology) and model based phylogenetic methods. We also explored the contribution of various data partitions to the phylogenetic pattern. The new genus forms part of a lineage that so far seems endemic to Australia and Tasmania. The addition of new taxa and the availability of data for some poorly studied genera provide new insights on tetragnathid phylogeny and evolution. posted 28 May 2008

Molecular markers reveal deep divergence in the Loxoscelesrufescens species group (Aranea: Sicariidae)

Greta J. Binford

Lewis & Clark College
Department of Biology
Portland, OR USA

Abstract: Loxosceles rufescens is a widespread species of Loxosceles with a putative native range stretching from North Africa and Mediterranean Europe to the Middle East and Asia. Delineation of this species has been challenged by a combination of low inter-population variation in genital morphology, human-mediated dispersal confounding boundaries of their native range, and limited understanding of related species in Northern and Central Africa. We used molecular phylogenetic and network analyses of L. rufescens populations from around the world to (1) distinguish between native and human-mediated ranges,  (2) identify populations divergent enough to warrant new species status within the L. rufescens species complex, and  (3) gain insight into their divergence from other Loxosceles in the context of the Gondwanan split and North African biogeography. Analyses showed strong support for a monophyletic group containing Brazilian L. amazonica, West African Loxosceles and all L. rufescens, corroborating previous evidence that the common ancestor of L. rufescens and L. amazonica predates the Gondwanan split.  A basal placement of some Moroccan and Canarian individuals within the L. rufescens clade and high percent divergences between some populations in this region and European, Asian and introduced populations suggest that L. rufescens’ presence in Northwest Africa predates humans and there is more diversity in this group than would be expected for a single species.  Morphological assessments of unidentified Central, Northern and Eastern African Loxosceles from various museum collections are underway and will help us better understand the extent of the range the L. rufescens species complex in Africa. posted 7 June 2008

Phylogenetic analysis of embryonic development in eleven species of spiders

Allison Edgar

Department of Biology
Reed College
Portland, Oregon USA

Abstract: The modes of embryonic development are potential characters for phylogenetic analyses. The development of two species, Cheiracanthium mildei and Latrodectus mactans, was investigated with time-lapse videography and histology; additional data on development in nine other species in eight families were coded from the literature.Several prominent heterochronies were detected, and these, along with time-independent morphological characters, were used to create a partial cladogram of the Araneae. This process recovered an accepted, although relatively poorly resolved, phylogeny, bearing a similarity to the tree proposed in Coddington (2005, in Ubick et al [eds.] Spiders of North America). Developmental character evolution was traced on a version of the Coddington tree, and suggested several developmental synapomorphies in the orb weavers + cobweb weavers, including the mode of gastrulation and sites of cell internalization. Moreover, a heterochronic shift in legbud appearance relative to the division of the left and right halves of the germ band mapped exclusively to the Entgelegynae. Developmental data, including the timing of events, may be a rich source of phylogenetic characters. posted 4 June 2008

Exotic spiders established in Florida: a threat to native species?

G. B. Edwards

Florida State Collection of Arthropods
Fla. Dept. Agric., Div. Plant Industry
Gainesville, FL USA

Abstract: At least 50 species of exotic spiders have been confirmed as established in Florida, and about half that many different species have been intercepted but have not become established.  The established exotic species are examined by origin, potential source of infestation, and habitat preference (feral or synanthropic).  Nearly half of the introduced species are primarily synanthropic or both synanthropic and feral, whereas most of the primarily feral species occur in disturbed habitats.  Nevertheless, reduced frequency of occurrence in collections in recent years suggests that populations of some native species may have been negatively affected by related or guild-similar invasive species. posted 6 June 2008

Character evolution in the genus Synsphyronus (Arachnida: Pseudoscorpiones: Garypidae)

M.S. Harvey

Western Australian Museum
Department of Terrestrial Invertebrates
Welshpool, Western Australia, AUSTRALIA

Abstract: Systematic biologists ask questions about character evolution in order to better understand the evolutionary history of organisms. I investigated the evolution of ecological and morphological characters in the pseudoscorpion genus Synsphyronus (Arachnida: Pseudoscorpiones: Garypidae).Synsphyronus are found throughout Australia in semi-arid and arid habitats including the granite outcrops of southwestern Australia, where at least four lineages have been recovered. Trichobothrial pattern and number of tarsi show exceptional patterns of variation in Synsphyronus, and these characters were heavily weighed in forming hypotheses of evolutionary relationships in the genus. Trichobothrial pattern is usually fixed at the genus level while the number of pedal tarsi is typically fixed at the family level in most pseudoscorpions. I first inferred a species level phylogeny using molecular data from mitochondrial (cytochrome oxidase) and nuclear (internal transcribed spacer region) genes.Parsimony and maximum likelihood methods were employed to reconstruct the evolutionary history of the characters on the estimated molecular phylogeny. I specifically tested whether trichobothria are lost but never gained, as predicted by the hypothesis that this character evolves by neoteny. Further, I tested the hypothesis that monotarsate taxa are monophyletic as outgroup comparison suggests. Finally, I investigated the ancestral habitat of Synsphyronus and the number of outcrop colonization events.Preliminary analyses suggest that trichobothria have been lost multiple times with no evidence of reversals and that the monotarsate species are not monophyletic. Ancestral state reconstruction analyses suggest that outcrops have been colonized several times. posted 7 June 2008

New molecular and morphological insights into the systematics of New World buthid scorpions

Scorpion Systematics Research Group
Division of Invertebrate Zoology
American Museum of Natural History
Central Park West at 79th Street
New York, NY U.S.A.

E.S. Volschenk

Department of Terrestrial Zoology
Western Australian Museum
Locked Bag 49
Welshpool DC, WA 6986, AUSTRALIA

Abstract: Scorpions in the New World buthid genera Centruroides Marx, 1890, Rhopalurus Thorell, 1876 and Tityus Koch, 1836 contain many of the world's most dangerously venomous species. Envenomation by these scorpions is a significant cause of morbidity and, in some cases, mortality in Mexico and the southwestern U.S.A., Central America, northern South America, and the Caribbean. Despite their medical importance, these genera are poorly defined and their relationships the subject of much speculation. New species continue to be discovered throughout their distribution and many putative widespread polymorphic species (according the biological species concept) turn out to be complexes of phylogenetic species upon reinvestigation. A morphological data matrix and DNA sequences from six loci in the nuclear (28S rDNA, 18S rDNA, Histone H3) and mitochondrial genomes (Cytochrome Oxidase I, 16S rDNA, 12S rDNA) were combined to produce a phylogeny with important implications for the evolutionary relationships among these genera. The diagnoses and current taxonomic status of some of the genera are discussed in light of the phylogeny. posted 28 May 2008, modified 17 June 2008

Spatial resolving power of peg sensilla on scorpion pectines

Douglas D. Gaffin

Department of Zoology
University of Oklahoma
Norman, OK USA

Abstract: Pectines are mid-ventral, comb-like, chemosensory organs on all scorpions. Scorpions lower their pectines to the ground in quick intermittent ‘taps’ that last fewer than 100 ms and use them to detect substrate-borne chemical cues. The distal, ground-facing surfaces of the pectinal ‘teeth’ have thousands of peg sensilla, the fundamental units of taste reception on these organs. Some sand scorpions have up to 10,000 pegs per mm² or hundreds of pegs in an area the size of a sand grain; biologists have wondered why scorpions have so many sensilla. I hypothesize that the pegs are functionally redundant and serve as parallel samplers for fast, across-tooth averaging of stimulant intensity. To learn more about why scorpions have so many units for taste reception, we measured the chemosensory response of peg sensilla moved within chemical gradients generated by static clouds of volatile compounds. Though instantaneous spiking frequency could not resolve stimulant intensity, it is possible to derive accurate, real-time information of stimulant concentration by parallel averaging of information from several pegs. By merging the electrophysiological data with the time constraints of a pectinal sniff and the density of pegs on a pectinal tooth, chemical concentration cannot be resolved with fewer than seven pegs. Taken together with previous morphological studies that show topographical maintenance of neural projections from pectinal teeth to the scorpion subesophageal ganglion, and the size relationship of scorpion teeth to substrate particles, it appears that the pectinal tooth is the basic unit of information relay to the scorpion brain. posted 7 June 2008

Molecular evolution and diversity of venom neurotoxins from black widow spiders

Department of Neurobiology
University of Arizona
Tucson, AZ USA

Cheryl Y. Hayashi

Department of Biology
University of California Riverside
Riverside, CA USA

Abstract: The venom of black widow spiders (genus Latrodectus) contains α-latrotoxin, a powerful neurotoxin that causes mass release of transmitters from vertebrate neurosecretory cells and severe envenomation in humans.  In addition to α-latrotoxin, Latrodectus venom contains other neurotoxins with similar molecular features but which selectively affect invertebrates. Collectively, these toxins are considered functionally distinct products of a single gene family (latrotoxins).  At the molecular level latrotoxins have been well characterized in a single Eurasian species (L. tredecimguttatus).  While latrotoxins are virtually unknown outside of L. tredecimguttatus, biochemical and clinical data suggest that these toxins occur in other Latrodectus species and related genera.  To further investigate latrotoxin diversity, we have determined sequences of the α-latrotoxin gene from multiple Latrodectus species.  Polypeptide sequences inferred from these data differ by many non-conservative amino acid substitutions, suggesting they may also exhibit significant functional differences in vertebrate toxicity.  We interpret this interspecific genetic variation in light of reported variation in vertebrate toxicity across Latrodectus and related species and consider its evolutionary significance. posted 19 May 2008

Seismic communication in Schizocosa ocreata (Hentz) wolf spiders:  Influence of substratum on mating success and behavioral compensation for environmental constraints

Shira D. Gordon

Department of Biological Sciences
University of Cincinnati
Cincinnati, OH

Abstract: Courtship displays of male Schizocosa ocreata (Hentz) wolf spiders are multimodal, and consist of visual signals (e.g. leg tapping, waving and arching) as well as seismic signals (e.g., stridulation, percussion).  In the complex forest floor habitat of S. ocreata, signals in one channel or another may be lost due to background noise or transmission properties of the environment, necessitating increased reliance on a single mode.  As the microhabitat consists primarily of leaf litter, with patches of wood/bark, bare soil and rock, each with different seismic transmission properties, we tested whether the efficacy of these substrata affected the courtship displays of male wolf spiders and male mating success.  In a habitat choice experiment, males and females visited each substratum with equal frequency, but spent longer periods of time on leaf litter. Use of seismic vs. visual signals varied significantly between substrata, and the frequency of certain visual displays (.e.g., leg waving and arching) was greater on rock and soil. Male courtship latency did not vary between substrata, but mating success was significantly greater on leaf litter. Our results indicate that males may compensate for limited transmission properties of certain substrata (e.g., rock, soil) by increasing time spent on others (leaf litter) and/or adding more visual courtship signaling behaviors.  These results indicate that while males may prefer a leaf litter substratum, they may be able to change their courtship behaviors depending on the substratum. posted 6 June 2008

Cytochrome oxidase I variation in agroecosystem linyphiids and lycosids

Matthew H. Greenstone

Invasive Insect Biocontrol & Behavior Laboratory
Agricultural Research Service, Beltsville, Maryland, USA

Department of Biology, University of Mississippi
Oxford, Mississippi, USA

Smithsonian Institution
National Museum of Natural History, Washington, District of Columbia, USA

Department of Entomology, University of Maryland
College Park, Maryland, USA

Abstract: Cytochrome Oxidase I (COI) is the most-used DNA barcoding sequence for animals, but little is known about its intra-specific variability in spiders. We present haplotype frequency data for five common agroecosystem linyphiids and lycosids. Variation is high in Florinda coccinea, Meioneta unimaculata, and Tennesseellum formicum, low in Pardosa milvina, and intermediate in Rabidosa rabida. Considering spider phylogenetic constraints and population size, crop physiognomy, and agronomic practices, we present hypotheses to explain these differences. The levels of variation observed are not likely to diminish the usefulness of COI for barcoding spiders; comparisons with congeners are needed to resolve this question. posted 17 April 2008

Pitfall trap designs to maximize spider richness and minimize amphibian by-catch

Clarisse Hart

Harvard University: Harvard Forest
Petersham, Massachusetts USA

Abstract: Pitfall trapping is the most common collection method in arachnological research. The pitfall trap’s ability to provide accurate richness estimates has been scrutinized, but little work has addressed the traps’ significant problem of capturing non-target amphibians and small mammals. Common modifications to the basic spider trap design (e.g., funnels and raised lids) serve directly to protect the trap from rain and debris, while indirectly minimizing by-catch of large and medium-sized animals. But these methods do not prevent capture of smaller amphibians, and furthermore are not systematically employed by all practitioners. I investigated the effects of four pitfall trap modifications on spider richness and small amphibian capture in a mixed hardwood/conifer forest in central Massachusetts. Five randomized replicates of eleven trap designs (raised lids, interior funnels, mesh collars, and solid collars) were set in rows spaced 20 meters apart over two spring weeks—the first week dry (4mm of rain) and the second wet (33mm of rain). Analysis showed that total spider richness at the family level was unaffected (p=0.07) by the trap modifications. Salamander capture (n=29 from 110 traps) was affected by the trap modifications (p=0.004), with unlidded traps across designs more likely (p=0.02) to result in salamander mortality. Between the two collection weeks, there were also differences in spider richness (p=0.003) and salamander capture rates (p=0.005), suggesting that precipitation may be an important factor to consider when analyzing richness data collected from pitfall traps. posted 7 June 2008

Uncovering old cryptic species in a dynamic Californian landscape:  Studies of the Antrodiaetus (Atypoides) riversi species complex

Department of Biology
San Diego State University
San Diego, CA USA

Graduate Program in Genetics, Genomics and Bioinformatics
University of California
Riverside, CA USA

Cheryl Hayashi

Department of Biology
University of California
Riverside, CA USA

Abstract: The antrodiaetid mygalomorph taxon Antrodiaetus (Atypoides) riversi is currently classified as a single species, following the taxonomy of Coyle (1968).  Both Ramirez & Chi (2004) and Starrett & Hedin (2007) used genetic data to argue for cryptic speciation within this taxon, the latter authors suggesting that perhaps five species exist under the current umbrella of A. riversi.  Here we extend our prior studies of this species complex with a specimen sample that includes spiders from over 100 populations; DNA sequence data from 4 different genes (one mitochondrial, 3 nuclear) are used to study phylogenetic divergence in this population sample.  Our analyses of these data support the following general conclusions: 1) the A. riversi complex likely includes eight separate species, all with relatively small allopatric and/or parapatric distributions, 2) phylogeographic structuring within species suggests extremely low levels of gene flow, for both female (mitochondrial) and bisexual (nuclear) genetic systems, 3) studies of genetic divergence where cryptic species come into contact provide no evidence for gene flow (i.e., genetic barriers seem complete where we’ve studied them), 4) two different species have geographic distributions that span the Central Valley in a similar fashion; this replicated “trans-Valley” event may have resulted from log rafting on ancient rivers.  In sum, studies of the A. riversi complex are providing a detailed glimpse into the biogeographic history of California, and invite many interesting questions regarding species delimitation and speciation mechanism in a highly genetically-structured system. posted 19 May 2008

Differences in male and female foraging:  Giant females play the lottery

Linden Higgins

Department of Biology, University of Vermont
Burlington, Vermont USA

Abstract: Spiders in the orb-weaving genus Nephila  are famous for their extreme sexual size dimorphism, which is due primarily to differences in the number of juvenile instars.   In addition, female N. clavipes show large amounts of variation in size and timing at maturity that is believed due primarily to differences in the number of juvenile instars.  To test this hypothesis, I reared spiders from eggs laid by females collected in several Mexican populations and one Texan population.  Spiderlings were randomly assigned to one of three different diets spanning the range observed in the field and reared to sexual maturity.  The rearing experiment showed several unexpected patterns.  First, there were sexual differences presumably related to small male size:  males from all populations were capable of reaching maturity on any diet, but only females from Texas could regularly reach maturity on the low or medium diets.  Second, female nutritional needs increased dramatically following the sixth molt.  Third, even on the highest diet, developmental rates slowed dramatically in the seventh and eighth instars.  I hypothesize that this may reflect the existence of a lottery-style life-history, where females are dependent upon the rare capture of large packages of resources in order to successfully reach maturity. posted 24 April 2008

Effects of thinning on spider diversity of a high elevation plantation forest in Taiwan

Pao Shen Huang

Dept of Entomology
National Chung-Hsing Univ.
Taichung 402, TAIWAN

Abstract: Spiders are one of the most dominant arthropods in forest ecosystems and are very sensitive to changes of the habitat. Studies about the effects of forest management on biodiversity in Asia are few and are mostly conducted in temperate areas such as Japan. How management affects biodiversity of tropical/subtropical forests in Asia is still not clear. In this study, the effects of management on biodiversity of a subtropical forest in Asia were assessed by comparing the community structure and guild composition of spiders in plantation forests receiving different degrees of thinning. The study site was located in a high elevation Chamaecyparis formosensis plantation in central Taiwan. Nine 10 m × 10 m sampling plots were established in C. formosensis plantations receiving no thinning, moderate thinning and heavy thinning. Another nine sampling plots were set up in a broadleaf forest nearby. From four collection trips conducted in 2005 and 2006, a total of 3484 spiders (141 species and 22 families) were obtained. Both abundance and species richness of primary and heavy thinning plantation forests were higher than the other forest types. Spider diversities differed significantly among four forest types, no matter estimated by species or family compositions. Spider guild composition did not differ significantly between no- thinning plantation and broadleaf forests, although all the other pair-wise comparisons were significant. While orb weavers were the dominant guild of plantation forests, space weavers were the most dominant in primary forests. Among various environmental factors measured, understory vegetation density and temperature were best correlated with the observed spider diversity variations. Such results indicated that in the high elevation C. formosensis plantation in Taiwan thinning practices altered spider diversities mainly through changes in understory vegetation structures. posted 7 June 2008

Assessing diversity of jumping spider’s spectral sensitivity