Huntsman spider phylogeny informs evolution of life history, egg sacs, and morphology.

Huntsman spiders (Araneae: Sparassidae) are among the most speciose spider families, with a near-worldwide distribution, diverse habitats, equally diverse life histories, and five prolonged subsocial species. Previous molecular phylogenies have focused on individual subfamilies or clades. Here, we provide a phylogenetic inference with broadened sampling from 37 genera and eight of the eleven sparassid subfamilies. We increased taxon sampling by including species not previously sequenced and most available data on GenBank of two mitochondrial (COI, 16S rRNA) and two nuclear (H3, 28S rRNA) genes for a total of 262 ingroup taxa and nine outgroup taxa. Divergence dates were estimated using outgroup fossil taxa suggesting the sparassids evolved âˆ¼ 100 mya (stem age), while the clade containing all subfamilies except Sparianthinae evolved âˆ¼ 90 mya (stem age). Using a stochastic map approach with 40 species, this is the first sparassid phylogeny to incorporate extensive biology and life history data. Correlations of life history traits with solitary, subsocial, and prolonged subsocial behavior are examined using the D-test. Sparassid sociality is associated with life history traits that allow developing spiders to remain in their natal retreat longer (e.g., larger permanent retreats, plastered egg sacs, and ontogenetically delayed foraging), but is unrelated to body size or lifespan. Detailed morphological scoring of the endemic Australian subfamily Deleninae contextualizes existing molecular data, including in the Isopeda-Holconia-Isopedella complex. This study supports the monophyly of many major lineages, including for the first time, the Sparianthinae, but indicates multiple clades (Sparassinae and Eusparassinae) are paraphyletic and need further revision.

Effects on running speed of changes in sexual size dimorphism at maturity on in the cursorial huntsman spider, Delena cancerides (Sparassidae).

Running speed is a measure of whole-organism performance reflecting relative fitness. For spiders, increased speed translates into enhanced prey capture, mating success and reduced predation risk. In male spiders, leg length increases dramatically with the molt to sexual maturity. To determine how changes in leg length and body mass with sexual maturity influence running performance, we compared allometric and kinematic changes in a species without extreme size sexual dimorphism (SSD): male and female Delena cancerides (Sparassidae) during their penultimate and adult instars. Spiders in each age-sex class were filmed running in the lab, and body morphometrics, maximum velocity, body lengths per second, acceleration, stride length and stride frequency were compared. At maturity, females increase in overall size, whereas male's leg length increases over 30% with little associated increase in body mass or overall size. Adult male legs are similar in length to those of the adult females and maximum velocity did not differ between age-sex classes. However, both male age-classes have higher velocity scaled as body lengths per second than females, due to their lighter mass. Thus, for sparassids spiders without large SSD, lower mass and longer legs translate into lower energetic costs of running distances for males.

A molecular phylogeny of the Australian huntsman spiders (Sparassidae, Deleninae): implications for taxonomy and social behaviour.

Huntsman spiders (Sparassidae) are a diverse group with a worldwide distribution, yet are poorly known both taxonomically and phylogenetically. They are particularly diverse in Australia where an endemic lineage, Deleninae, has diversified to form nearly 100 species. One unusual species, Delena cancerides, has been believed to be the sole group-living sparassid. Unlike all of the other subsocial and social spiders which are capture-web based or live in silken tunnels, D. cancerides are non-web building spiders that live in large matrilineal colonies of a single adult female and her offspring from multiple clutches of under the bark of dead trees. Here we report the discovery of two additional prolonged subsocial sparassid species, currently in Eodelena but here formally proposed as a synonomy of Delena (new synonoymy), Delena (Eodelena) lapidicola and D. (E.) melanochelis. We briefly describe their social demographics, behavior, and habitat use. In order to understand the evolutionary relationships among these species, and thus origin of sociality and other traits in this group, we also offer the first molecular phylogeny of Deleninae and relatives. We employ model based phylogenetic analyses on two mtDNA and three nuDNA loci using maximum likelihood and Bayesian methods, including both 'classical' concatenation approach as well as coalescent-based analysis of species trees from gene trees. Our results support the hypothesis that the delenine huntsman spiders are a monophyletic Australian radiation, approximately 23 million year old, and indicate that the current ten genera should be merged to six genera in four clades. Our findings are inconsistent with some relatively recent changes in the taxonomy of Deleninae. The three known group-living delenine species are related and likely represent a single origin of sociality with a single reversal to solitary life-styles. Our results provide strong support for the classical Isopeda, but not for the recent splitting of that taxon into Isopeda, Isopedella, and Holconia. Another moderately supported clade within Deleninae unites three genera (Pediana, Beregama, Typostola) that, while morphologically diverse, all share extraordinary locomotory speed. A fourth clade is comprised of the speciose Neosparassus, containing Zachria. In sum, our study results in a robust phylogeny of Deleninae, casting light on the origin of sociality in the group, and facilitating future work on these unusual spiders.

Molecular, morphological, and life history data to support research of huntsman spiders (Araneae: Sparassidae).

This article on biodiversity and life history data in huntsman spiders (Araneae: Sparassidae) includes the following: molecular data deposited on GenBank for 72 individuals representing 27 species in seven subfamilies, life history and behavioral data on 40 huntsman species from over two decades of observations, and morphological data for 26 species in the subfamily Deleninae as well as an undescribed representative of the genus Damastes. Molecular data include the nuclear genes histone H3 (H3) and 28S ribosomal RNA (28S rRNA), mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) were sequenced via Sanger sequencing by J.A. Gorneau. Life history data were collected in the field and in the lab by L.S. Rayor and include data on age at sexual maturity, lifespan, social classification, egg sac shape, how the egg sac is attached or carried, retreat location, retreat modification, retreat size relative to adult female body size, approximate mean body mass, and mean cephalothorax width. Morphological data on Deleninae and one Damastes sp. were scored by C.A. Rheims and includes information on the following characters: prosoma (fovea, posterior eye row shape (PER), anterior median eye (AME) diameter, AME-AME and PME-PME interdistances), male palp (embolic sclerite (PS), conductor sclerotized base (SB), tegular apophysis (TA), flange (f)) and female epigyne and vulva (epigynal sclerite (ES), spermathecal sacs (SS)). These data were used to clarify relationships among the Australian endemic Deleninae, as well as global patterns in sparassid evolution. The data demonstrate phylogenetic patterns in life history, social evolution, and natural history among the sparassids. These data contribute to future comparative research on sparassid systematics, evolution, and behavior. This data article complements a research article published in Molecular Phylogenetics and Evolution [1].

Genomic signatures of recent convergent transitions to social life in spiders.

The transition from solitary to social life is a major phenotypic innovation, but its genetic underpinnings are largely unknown. To identify genomic changes associated with this transition, we compare the genomes of 22 spider species representing eight recent and independent origins of sociality. Hundreds of genes tend to experience shifts in selection during the repeated transition to social life. These genes are associated with several key functions, such as neurogenesis, behavior, and metabolism, and include genes that previously have been implicated in animal social behavior and human behavioral disorders. In addition, social species have elevated genome-wide rates of molecular evolution associated with relaxed selection caused by reduced effective population size. Altogether, our study provides unprecedented insights into the genomic signatures of social evolution and the specific genetic changes that repeatedly underpin the evolution of sociality. Our study also highlights the heretofore unappreciated potential of transcriptomics using ethanol-preserved specimens for comparative genomics and phylotranscriptomics.

Ontogenetic shifts within the selfish herd: predation risk and foraging trade-offs change with age in colonial web-building spiders.

We examine costs and benefits associated with spatial position relative to spider age (size) in colonial web-building spiders. Predator attack and capture rates vary with position in the colony, and suggest that risk is higher for the smallest and the largest spiders on the periphery, and lower in the central core of the colony. Foraging success is greater on the periphery for small and medium spiders but does not differ significantly with position for larger spiders. Decreased predation risk may be the reason why larger spiders aggressively seek and defend positions in the colony core, demonstrating a "selfish herd effect" (Rayor and Uetz, 1990). Smaller (immature) spiders, unable to compete for protected web positions in the core, must trade-off potentially higher risk of predation to take advantage of higher prey availability on the periphery. Increased foraging success on the periphery may allow juvenile spiders to achieve the larger size necessary to compete successfully for protected core positions as adults. Spatial variation in size-related fitness trade-offs between predation risk and foraging success may explain why colonies are dynamic entities - with individual spiders exhibiting ontogenetic shifts in web location as they grow larger and mature-accounting for the characteristic age (size) structure ofMetepeira incrassata colonies.

Maternal care and subsocial behaviour in spiders.

While most spiders are solitary and opportunistically cannibalistic, a variety of social organisations has evolved in a minority of spider species. One form of social organisation is subsociality, in which siblings remain together with their parent for some period of time but disperse prior to independent reproduction. We review the literature on subsocial and maternal behaviour in spiders to highlight areas in which subsocial spiders have informed our understanding of social evolution and to identify promising areas of future research. We show that subsocial behaviour has evolved independently at least 18 times in spiders, across a wide phylogenetic distribution. Subsocial behaviour is diverse in terms of the form of care provided by the mother, the duration of care and sibling association, the degree of interaction and cooperation among siblings, and the use of vibratory and chemical communication. Subsocial spiders are useful model organisms to study various topics in ecology, such as kin recognition and the evolution of cheating and its impact on societies. Further, why social behaviour evolved in some lineages and not others is currently a topic of debate in behavioural ecology, and we argue that spiders offer an opportunity to untangle the ecological causes of parental care, which forms the basis of many other animal societies.

Predatory behavior of Polistes dominulus wasps in response to cardenolides and glucosinolates in Pieris napi caterpillars.

To examine how plant allelochemicals in prey affect foraging choices made by generalist predator paper wasps, Polistes dominulus (Vespidae), we compared predation on Pieris napi (Pieridae) caterpillars reared on host plants with different allelochemicals. In naturalistic behavioral choice experiments, free-flying wasps chose between living pierids reared on cabbage (Brassica oleracea), which lacks deterrent allelochemicals, or alternate host plants with potentially deterrent allelochemicals. The alternative host plants were: wormwood mustard, (Erysimum cheiranthoides: Brassicaceae), which contains cardenolides; nasturtium (Tropaeolum majus: Tropaeolaceae) with high concentrations of chlorogenic acid; and black mustard (Brassica nigra: Brassicaceae) with high concentrations of the aliphatic glucosinolate, sinigrin. Although wasps captured equal numbers of caterpillars reared on cabbage and each alternate host plant, they spent significantly longer handling prey from the alternate host plants as they selectively removed the caterpillar's gut, which contained the plant material. This was true even if the caterpillar did not sequester toxins in its tissues, as revealed by high performance liquid chromatography (HPLC) analysis of Erysimum-reared pierids. Because handling time is longer, predators that capture pierids containing non-sequestered allelochemicals experience an overall reduction in foraging rate that may translate into a fitness cost.