Extant primitively segmented spiders have recently diversified from an ancient lineage

Seven new species of the segmented spider genus Liphistius (Mesothelae, Liphistiidae) in Thailand and Myanmar

Seven new species of the primitive segmented spider genus Liphistius are described and assigned to species groups based on characters of the male palp and vulva plate. The bristowei group includes L.dawei Sivayyapram & Warrit, sp. nov. (♂♀) from southeastern Myanmar, L.choosaki Sivayyapram & Warrit, sp. nov. (♀) from northwestern Thailand, and L.lansak Sivayyapram & Warrit, sp. nov. (♀) from western Thailand; the trang group (Complex A) contains L.kaengkhoi Sivayyapram & Warrit, sp. nov. (♂♀), L.hintung Sivayyapram & Warrit, sp. nov. (♂♀), L.buyphradi Sivayyapram & Warrit, sp. nov. (♂♀), and L.champakpheaw Sivayyapram & Warrit, sp. nov. (♂♀) from central Thailand.

Eyeless cave-dwelling Leptonetela spiders still rely on light

Subterranean animals living in perpetual darkness may maintain photoresponse. However, the evolutionary processes behind the conflict between eye loss and maintenance of the photoresponse remain largely unknown. We used Leptonetela spiders to investigate the driving forces behind the maintenance of the photoresponse in cave-dwelling spiders. Our behavioral experiments showed that all eyeless/reduced-eyed cave-dwelling species retained photophobic response and that they had substantially decreased survival at cave entrances due to weak drought resistance. The transcriptomic analysis demonstrated that nearly all phototransduction pathway genes were present and that all tested phototransduction pathway genes were subjected to strong functional constraints in cave-dwelling species. Our results suggest that cave-dwelling eyeless spiders still use light and that light detection likely plays a role in avoiding the cave entrance habitat. This study confirms that some eyeless subterranean animals have retained their photosensitivity due to natural selection and provides a case of mismatch between phenotype and genotype or physiological function in a long-term evolutionary process.

Advances in the reconstruction of the spider tree of life: A roadmap for spider systematics and comparative studies

In the last decade and a half, advances in genetic sequencing technologies have revolutionized systematics, transforming the field from studying morphological characters or a few genetic markers, to genomic datasets in the phylogenomic era. A plethora of molecular phylogenetic studies on many taxonomic groups have come about, converging on, or refuting prevailing morphology or legacy-marker-based hypotheses about evolutionary affinities. Spider systematics has been no exception to this transformation and the inter-relationships of several groups have now been studied using genomic data. About 51 500 extant spider species have been described, all with a conservative body plan, but innumerable morphological and behavioural peculiarities. Inferring the spider tree of life using morphological data has been a challenging task. Molecular data have corroborated many hypotheses of higher-level relationships, but also resulted in new groups that refute previous hypotheses. In this review, we discuss recent advances in the reconstruction of the spider tree of life and highlight areas where additional effort is needed with potential solutions. We base this review on the most comprehensive spider phylogeny to date, representing 131 of the 132 spider families. To achieve this sampling, we combined six Sanger-based markers with newly generated and publicly available genome-scale datasets. We find that some inferred relationships between major lineages of spiders (such as Austrochiloidea, Palpimanoidea and Synspermiata) are robust across different classes of data. However, several new hypotheses have emerged with different classes of molecular data. We identify and discuss the robust and controversial hypotheses and compile this blueprint to design future studies targeting systematic revisions of these problematic groups. We offer an evolutionary framework to explore comparative questions such as evolution of venoms, silk, webs, morphological traits and reproductive strategies.

Three new species of the primitively segmented spider genus Songthela (Mesothelae, Liphistiidae, Heptathelinae) from Hunan Province, China

Three new species of the primitively segmented spider genus Songthela Ono, 2000 are identified and described from Hunan Province, China, based on morphological characters of males and females: S. anhua Zhang & Xu, sp. nov. (♂♀), S. longhui Zhang & Xu, sp. nov. (♂♀), and S. zhongpo Zhang & Xu, sp. nov. (♂♀). All the new Songthela species belong to the multidentata-group according to male palp and female genital morphology.

An integrative approach reveals high species diversity in the primitively segmented spider genus

Accurate species delimitation is crucial for our understanding of evolution, biodiversity and conservation. However, morphology-based species delimitation alone appears to be prone to taxonomic errors and ineffective for taxa with high interspecific morphological homogeneity or intraspecific morphological variations, as is the case for mesothele and mygalomorph spiders. Combined molecular–morphology species delimitation has shown great potential to delimit species boundaries in such ancient lineages. In the present study, molecular and morphological evidence were integrated to delimit species of the primitively segmented spider genus Songthela Ono, 2000. The cytochrome c oxidase subunit I gene (COI) was sequenced for 192 novel specimens belonging to 12 putative morphospecies. The evolutionary relationships within Songthela and the 12-morphospecies hypothesis were tested in two steps – species discovery and species validation – using four single-locus species delimitation approaches. All species delimitation analyses supported the 12-species hypothesis. Phylogenetic analyses yielded three major clades in Songthela, which are consistent with morphology. Accordingly, we assigned 19 known and 11 new species (S. aokoulong, sp. nov., S. bispina, sp. nov., S. dapo, sp. nov., S. huayanxi, sp. nov., S. lianhe, sp. nov., S. lingshang, sp. nov., S. multidentata, sp. nov., S. tianmen, sp. nov., S. unispina, sp. nov., S. xiujian, sp. nov., S. zizhu, sp. nov.) of Songthela to three species-groups: the bispina-group, the multidentata-group and the unispina-group. Another new species, S. zimugang, sp. nov., is not included in any species groups, but forms a sister lineage to the bispina- and unispina-groups. These results elucidate a high species diversity of Songthela in a small area and demonstrate that integrating morphology with COI-based species delimitation is fast and cost-effective in delimiting species boundaries. http://zoobank.org/urn:lsid:zoobank.org:pub:AF0F5B31-AFAF-4861-9844-445AE8678B67

Four new species of the primitively segmented spider genus Songthela (Mesothelae, Liphistiidae) from Chongqing Municipality, China

This paper reports four new species of the primitively segmented spider genus Songthela from Chongqing Municipality, China, based on morphological characters of both males and females: S. jinyun sp. nov., S. longbao sp. nov., S. serriformis sp. nov. and S. wangerbao sp. nov. We also provide the GenBank accession codes of mitochondrial DNA barcode gene, cytochrome c oxidase subunit I (COI), for the holotype of four new species for future identification.  

Three new species of the primitively segmented spider genus Songthela (Araneae, Mesothelae) from Guizhou Province, China

We diagnose and describe three new species of the primitively segmented spider genus Songthela from Guizhou Province, China, based on morphological characters and molecular data: S.liuisp. nov. (♂♀), S.tianzhusp. nov. (♂♀), and S.yupingsp. nov. (♂♀). We provide the genetic distances within and among the three new species based on the DNA barcode gene, cytochrome c oxidase subunit I (COI) to support our descriptions. We also provide the COI GenBank accession codes for the three new species for future identification.

A new species of Liphistius from Myanmar and description of the actual male of L. birmanicus Thorell, 1897 (Araneae, Mesothelae, Liphistiidae)

Five Liphistius Schiödte, 1849 species of the primitively segmented spider family Liphistiidae are currently known from Myanmar. Here, we described a new species, Liphistius pyinoolwin sp. nov. (♂♀), which was collected from Pyin Oo Lwin, Mandalay Region, Myanmar, diagnosed based on its genital morphology. The specimens (2♂♂, 5♀♀) collected by Walter C. Sedgwick from Pyin Oo Lwin in 1982 were misidentified as L. birmanicus Thorell, 1897 and are treated here as the newly described species. Accordingly, we described the males of L. birmanicus for the first time, redescribed its female, using newly collected specimens from Yadò, Than Taung and Kalekho Atet townships, Kayin State. We also provided information on the variation in genital morphology of both species, and their relationships within the birmanicus-group of species.

Three new species of the segmented spider genus Qiongthela (Mesothelae, Liphistiidae) from Hainan Island, China

We report three new species of the segmented trapdoor spider genus Qiongthela Xu & Kuntner, 2015 collected from Hainan Island, China based on morphological characters: Q.dongfangsp. nov. (♂♀), Q.nankaisp. nov. (♂♀), Q.yalinsp. nov. (♂♀). We also provide the GenBank accession codes of the DNA barcode gene, cytochrome c oxidase subunit I (COI), of the type specimens of all three new species to aid future identification.

Spider Diversification Through Space and Time

Spiders (Araneae) make up a remarkably diverse lineage of predators that have successfully colonized most terrestrial ecosystems. All spiders produce silk, and many species use it to build capture webs with an extraordinary diversity of forms. Spider diversity is distributed in a highly uneven fashion across lineages. This strong imbalance in species richness has led to several causal hypotheses, such as codiversification with insects, key innovations in silk structure and web architecture, and loss of foraging webs. Recent advances in spider phylogenetics have allowed testing of some of these hypotheses, but results are often contradictory, highlighting the need to consider additional drivers of spider diversification. The spatial and historical patterns of diversity and diversification remain contentious. Comparative analyses of spider diversification will advance only if we continue to make progress with studies of species diversity, distribution, and phenotypic traits, together with finer-scale phylogenies and genomic data.

Phylogenetic Systematics and Evolution of the Spider Infraorder Mygalomorphae Using Genomic Scale Data

The infraorder Mygalomorphae is one of the three main lineages of spiders comprising over 3000 nominal species. This ancient group has a worldwide distribution that includes among its ranks large and charismatic taxa such as tarantulas, trapdoor spiders, and highly venomous funnel-web spiders. Based on past molecular studies using Sanger-sequencing approaches, numerous mygalomorph families (e.g., Hexathelidae, Ctenizidae, Cyrtaucheniidae, Dipluridae, and Nemesiidae) have been identified as non-monophyletic. However, these data were unable to sufficiently resolve the higher-level (intra- and interfamilial) relationships such that the necessary changes in classification could be made with confidence. Here, we present a comprehensive phylogenomic treatment of the spider infraorder Mygalomorphae. We employ 472 loci obtained through anchored hybrid enrichment to reconstruct relationships among all the mygalomorph spider families and estimate the timeframe of their diversification. We sampled nearly all currently recognized families, which has allowed us to assess their status, and as a result, propose a new classification scheme. Our generic-level sampling has also provided an evolutionary framework for revisiting questions regarding silk use in mygalomorph spiders. The first such analysis for the group within a strict phylogenetic framework shows that a sheet web is likely the plesiomorphic condition for mygalomorphs, as well as providing insights to the ancestral foraging behavior for all spiders. Our divergence time estimates, concomitant with detailed biogeographic analysis, suggest that both ancient continental-level vicariance and more recent dispersal events have played an important role in shaping modern day distributional patterns. Based on our results, we relimit the generic composition of the Ctenizidae, Cyrtaucheniidae, Dipluridae, and Nemesiidae. We also elevate five subfamilies to family rank: Anamidae (NEW RANK), Euagridae (NEW RANK), Ischnothelidae (NEW RANK), Pycnothelidae (NEW RANK), and Bemmeridae (NEW RANK). Three families Entypesidae (NEW FAMILY), Microhexuridae (NEW FAMILY), and Stasimopidae (NEW FAMILY), and one subfamily Australothelinae (NEW SUBFAMILY) are newly proposed. Such a major rearrangement in classification, recognizing nine newly established family-level rank taxa, is the largest the group has seen in over three decades. [Biogeography; molecular clocks; phylogenomics; spider web foraging; taxonomy.].

Molecular species delimitation in the primitively segmented spider genus Heptathela endemic to Japanese islands

Determining species boundaries forms an important foundation for biological research. However, the results of molecular species delimitation can vary with the data sets and methods that are used. Here we use a two-step approach to delimit species in the genus Heptathela, a group of primitively segmented trapdoor spiders that are endemic to Japanese islands. Morphological evidence suggests the existence of 19 species in the genus. We tested this initial species hypothesis by using six molecular species-delimitation methods to analyse 180 mitochondrial COI sequences of Heptathela sampled from across the known range of the genus. We then conducted a set of more focused analyses by sampling additional genetic markers from the subset of taxa that were inconsistently delimited by the single-locus analyses of mitochondrial DNA. Multilocus species delimitation was performed using two Bayesian approaches based on the multispecies coalescent. Our approach identified 20 putative species among the 180 sampled individuals of Heptathela. We suggest that our two-step approach provides an efficient strategy for delimiting species while minimizing costs and computational time.

Two new species of the primitively segmented spider genus Songthela from Hunan Province, China (Mesothelae, Liphistiidae)

This study reports two new species of the primitively segmented spider genus Songthela from Hunan Province, China, based on morphological characters: S.huangyangsp. nov. (♂♀), S.xiangnansp. nov. (♂♀). Additional material also facilitates a more accurate description of S.goulouensis (Yin, 2001) with the first description of the male. Nucleotide data for the barcoding gene, cytochrome c oxidase subunit I (COI), is also provided for these three species.

Four new species of the primitively segmented spider genus Qiongthela from Hainan Island, China (Mesothelae, Liphistiidae)

The primitively segmented spider genus Qiongthela Xu & Kuntner, 2015 consists of seven species that are distributed in Hainan Island, China and southern Vietnam. Of the seven species, five are known from Hainan Island. In this study, four more Qiongthela species collected from Hainan Island are diagnosed and described as new to science based on morphological characters: Q. baoting sp. nov. (♂♀), Q. qiongzhong sp. nov. (♂♀), Q. sanya sp. nov. (♂♀), Q. yinggezui sp. nov. (♂♀). To facilitate future identification, the GenBank accession codes of the DNA barcode gene, cytochrome c oxidase subunit I (COI), for all the type specimens are also provided.

The fossil record of spiders revisited: implications for calibrating trees and evidence for a major faunal turnover since the Mesozoic

Studies in evolutionary biology and biogeography increasingly rely on the estimation of dated phylogenetic trees using molecular clocks. In turn, the calibration of such clocks is critically dependent on external evidence (i.e. fossils) anchoring the ages of particular nodes to known absolute ages. In recent years, a plethora of new fossil spiders, especially from the Mesozoic, have been described, while the number of studies presenting dated spider phylogenies based on fossil calibrations increased sharply. We critically evaluate 44 of these studies, which collectively employed 67 unique fossils in 180 calibrations. Approximately 54% of these calibrations are problematic, particularly regarding unsupported assignment of fossils to extant clades (44%) and crown (rather than stem) dating (9%). Most of these cases result from an assumed equivalence between taxonomic placement of fossils and their phylogenetic position. To overcome this limitation, we extensively review the literature on fossil spiders, with a special focus on putative synapomorphies and the phylogenetic placement of fossil species with regard to their importance for calibrating higher taxa (families and above) in the spider tree of life. We provide a curated list including 41 key fossils intended to be a basis for future estimations of dated spider phylogenies. In a second step, we use a revised set of 23 calibrations to estimate a new dated spider tree of life based on transcriptomic data. The revised placement of key fossils and the new calibrated tree are used to resolve a long-standing debate in spider evolution - we tested whether there has been a major turnover in the spider fauna between the Mesozoic and Cenozoic. At least 17 (out of 117) extant families have been recorded from the Cretaceous, implying that at least 41 spider lineages in the family level or above crossed the Cretaeous-Paleogene (K-Pg) boundary. The putative phylogenetic affinities of families known only from the Mesozoic suggest that at least seven Cretaceous families appear to have no close living relatives and might represent extinct lineages. There is no unambiguous fossil evidence of the retrolateral tibial apophysis clade (RTA-clade) in the Mesozoic, although molecular clock analyses estimated the major lineages within this clade to be at least ∼100 million years old. Our review of the fossil record supports a major turnover showing that the spider faunas in the Mesozoic and the Cenozoic are very distinct at high taxonomic levels, with the Mesozoic dominated by Palpimanoidea and Synspermiata, while the Cenozoic is dominated by Araneoidea and RTA-clade spiders.

A taxonomic monograph of the liphistiid spider genus Heptathela, endemic to Japanese islands

Among the eight extant genera of primitively segmented spiders, family Liphistiidae, two are confined to East Asian islands, Heptathela Kishida, 1923 and Ryuthela Haupt, 1983. In this paper, a taxonomic revision of the genus Heptathela (Heptathelinae) from Kyushu and Ryukyu archipelago, Japan is provided. This study follows a multi-tier species delimitation strategy within an integrative taxonomic framework that is presented in a parallel paper, in which diagnosable lineages are considered as valid species. There, the initial hypothesis of species diversity (19) based on classical morphological diagnoses is tested with multiple species delimitation methods aimed at resolving conflict in data. This revision follows those analyses that converge on the species diversity of 20, which includes a pair of cryptic species that would have been undetected with morphology alone. After this revision, eight previously described species remain valid, two junior synonyms are proposed, and 12 new Heptathela species are described based on diagnostic evidence. To ease identification and to hint at putative evolutionary units, Heptathela is divided into three groups. The Kyushu group contains H.higoensis Haupt, 1983, H.kikuyai Ono, 1998, H.kimurai (Kishida, 1920), and H.yakushimaensis Ono, 1998; the Amami group contains H.amamiensis Haupt, 1983, H.kanenoi Ono, 1996, H.kojimasp. nov., H.sumiyosp. nov., and H.ukensp. nov.; and the Okinawa group contains H.yanbaruensis Haupt, 1983, H.ahasp. nov., H.gayozansp. nov., H.kubayamasp. nov., H.maesp. nov., H.otohasp. nov., H.shurisp. nov., H.tokashikisp. nov., H.untensp. nov., and H.cryptasp. nov.Heptathelahelios Tanikawa & Miyashita, 2014 is not assigned to a species group. A combination of diagnostic tools augments the morphological diagnoses that, in isolation, would be prone to error in morphologically challenging groups of organisms.

Two new species of the primitively segmented spider genus Liphistius Schiödte, 1849 (Mesothelae, Liphistiidae) from Myanmar

Two Liphistius species of the primitively segmented spider family Liphistiidae, collected from Loikaw (Kayah State) and Pinlaung (Shan State), Myanmar, are diagnosed and described as new to science based on their genital morphology: Liphistiushprusosp. nov. (♀), Liphistiuspinlaungsp. nov. (♂♀).

Biogeography of the Caribbean Cyrtognatha spiders

Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus Cyrtognatha (Tetragnathidae) from the Caribbean, with the aims to reconstruct its evolutionary history, examine its biogeographic history in the archipelago, and to estimate the timing and route of Caribbean colonization. Specifically, we test if Cyrtognatha biogeographic history is consistent with an ancient vicariant scenario (the GAARlandia landbridge hypothesis) or overwater dispersal. We reconstructed a species level phylogeny based on one mitochondrial (COI) and one nuclear (28S) marker. We then used this topology to constrain a time-calibrated mtDNA phylogeny, for subsequent biogeographical analyses in BioGeoBEARS of over 100 originally sampled Cyrtognatha individuals, using models with and without a founder event parameter. Our results suggest a radiation of Caribbean Cyrtognatha, containing 11 to 14 species that are exclusively single island endemics. Although biogeographic reconstructions cannot refute a vicariant origin of the Caribbean clade, possibly an artifact of sparse outgroup availability, they indicate timing of colonization that is much too recent for GAARlandia to have played a role. Instead, an overwater colonization to the Caribbean in mid-Miocene better explains the data. From Hispaniola, Cyrtognatha subsequently dispersed to, and diversified on, the other islands of the Greater, and Lesser Antilles. Within the constraints of our island system and data, a model that omits the founder event parameter from biogeographic analysis is less suitable than the equivalent model with a founder event.

Two new species of the purse-web spider genus Atypus Latreille, 1804 from Hainan Island, China (Araneae, Atypidae)

Two species of the purse-web spider genus Atypus Latreille, 1804 collected from Hainan Island, China, are diagnosed and described as new to science based on genital morphology, A. baotingensissp. n. (♂♀) and A. jianfengensissp. n. (♀). The DNA barcodes of the two species are also provided for future use.

Four new species of the primitively segmented spider genus Qiongthela from Hainan island, China (Mesothelae, Liphistiidae)

Four species of the primitively segmented spider genus Qiongthela Xu & Kuntner, 2015 collected from Hainan Island, China are diagnosed and described as new to science based on their genital morphology: Q. bawangsp. n. (♀), Q. jianfengsp. n. (♂♀), Q. yinisp. n. (♀), Q. wuzhisp. n. (♂♀). Together with the type species of Qiongthela, Q. baishensis Xu, 2015, five species are found and described from Hainan, China, and seven species are now known in the genus.

A genus-level taxonomic review of primitively segmented spiders (Mesothelae, Liphistiidae)

The spider suborder Mesothelae, containing a single extant family Liphistiidae, represents a species-poor and ancient lineage. These are conspicuous spiders that primitively retain a segmented abdomen and appendage-like spinnerets. While their classification history is nearly devoid of phylogenetic hypotheses, we here revise liphistiid genus level taxonomy based on original sampling throughout their Asian range, and on the evidence from a novel molecular phylogeny. By combining morphological and natural history evidence with phylogenetic relationships in the companion paper, we provide strong support for the monophyly of Liphistiidae, and the two subfamilies Liphistiinae and Heptathelinae. While the former only contains Liphistius Schiödte, 1849, a genus distributed in Indonesia (Sumatra), Laos, Malaysia, Myanmar, Thailand, we recognize and diagnose seven heptatheline genera, all but three removed from the synonymy of Heptathela: i) Ganthela Xu & Kuntner, gen. n. with the type species Ganthelayundingensis Xu, sp. n. is known from Fujian and Jiangxi, China; ii) a rediagnosed Heptathela Kishida, 1923 is confined to the Japanese islands (Kyushu and Okinawa); iii) Qiongthela Xu & Kuntner, gen. n. with the type species Qiongthelabaishensis Xu, sp. n. is distributed disjunctly in Hainan, China and Vietnam; iv) Ryuthela Haupt, 1983 is confined to the Ryukyu archipelago (Japan); v) Sinothela Haupt, 2003 inhabits Chinese areas north of Yangtze; vi) Songthela Ono, 2000 inhabits southwest China and northern Vietnam; and vii) Vinathela Ono, 2000 (Abcathela Ono, 2000, syn. n.; Nanthela Haupt, 2003, syn. n.) is known from southeast China and Vietnam.