Project description:BackgroundMygalomorph spiders represent a diverse, yet understudied lineage for which genomic level data has only recently become accessible through high-throughput genomic and transcriptomic sequencing methods. The Aptostichus atomarius species complex (family Euctenizidae) includes two coastal dune endemic members, each with inland sister species - affording exploration of dune adaptation associated patterns at the transcriptomic level. We apply an RNAseq approach to examine gene family conservation across the species complex and test for patterns of positive selection along branches leading to dune endemic species.ResultsAn average of ~ 44,000 contigs were assembled for eight spiders representing dune (n = 2), inland (n = 4), and atomarius species complex outgroup taxa (n = 2). Transcriptomes were estimated to be 64% complete on average with 77 spider reference orthologs missing from all taxa. Over 18,000 orthologous gene clusters were identified within the atomarius complex members, > 5000 were detected in all species, and ~ 4700 were shared between species complex members and outgroup Aptostichus species. Gene family analysis with the FUSTr pipeline identified 47 gene families appearing to be under selection in the atomarius ingroup; four of the five top clusters include sequences strongly resembling other arthropod venom peptides. The COATS pipeline identified six gene clusters under positive selection on branches leading to dune species, three of which reflected the preferred species tree. Genes under selection were identified as Cytochrome P450 2c15 (also recovered in the FUSTr analysis), Niemann 2 Pick C1-like, and Kainate 2 isoform X1.ConclusionsWe have generated eight draft transcriptomes for a closely related and ecologically diverse group of trapdoor spiders, identifying venom gene families potentially under selection across the Aptostichus atomarius complex and chemosensory-associated gene families under selection in dune endemic lineages.

Project description:This systematic study documents the taxonomy, diversity, and distribution of 40 species of the predominately Californian trapdoor spider genus Aptostichus Simon, 1891. Thirty-three of these species are newly described: Aptostichus dantrippi, Aptostichus cabrillo, Aptostichus pennjillettei, Aptostichus asmodaeus, Aptostichus nateevansi, Aptostichus chiricahua, Aptostichus icenoglei, Aptostichus isabella, Aptostichus muiri, Aptostichus barackobamai, Aptostichus sinnombre, Aptostichus hedinorum, Aptostichus aguacaliente, Aptostichus chemehuevi, Aptostichus sarlacc, Aptostichus derhamgiulianii, Aptostichus anzaborrego, Aptostichus serrano, Aptostichus mikeradtkei, Aptostichus edwardabbeyi, Aptostichus killerdana, Aptostichus cahuilla, Aptostichus satleri, Aptostichus elisabethae, Aptostichus fornax, Aptostichus lucerne, Aptostichus fisheri, Aptostichus bonoi, Aptostichus cajalco, Aptostichus sierra, Aptostichus huntington, Aptostichus dorothealangeae, and Aptostichus chavezi. Most of these species are restricted to the California Floristic Province, a known biodiversity hotspot. Of the 40 recognized species, over half are considered to be imperiled or vulnerable and two have likely gone extinct over the past half-century; the conservation status of only 11 species is considered to be secure. Using 73 quantitative and qualitative morphological characters I propose a preliminary phylogeny for the genus that recognizes four major lineages: the Atomarius, Simus, Hesperus, and Sierra species groups. Additionally, the phylogenetic analysis indicates that adaptations favoring the invasion of the arid desert habitats of southern California have evolved multiple times across the group. The existence of both desert and non - desert species in three of the four species groups makes this genus an ideal candidate for the study of the evolutionary ecology of desert arthropods. A set of molecular characters based on the contiguous mitochondrial DNA genes 16S-tRNA valine-12S is used in an independent analysis to assist in placement of specimens into species. The taxonomy section explicitly identifies the concept employed in species delimitation. Niche based distribution models are constructed to predict the ranges of species for which an adequate number of sampling sites were known.

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Aptostichus stephencolberti

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