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ABSTRACT The family Dysderidae is a highly diverse group of nocturnal ground‐dwelling and active‐hunter spiders. Dysderids are mostly restricted to the Western Palearctic, and particularly rich and abundant around the Mediterranean region. Interestingly, the distribution of species richness among its 24 genera and three subfamilies is highly biased—80% of its 644 documented species belong to just two genera, Dysdera (326) and Harpactea (211). Dysderidae provides an excellent study case for evolutionary and ecological research. It includes cases of trophic specialization, which are uncommon among spiders, and exhibit other remarkable biological (e.g. holocentric chromosomes), behavioural (e.g. cryptic female choice), evolutionary (e.g. adaptive radiation) and ecological features (e.g. recurrent colonization of the subterranean environment). The lack of a quantitative hypothesis on its phylogenetic structure has hampered its potential as a testing ground for evolutionary, biogeographical and ecological hypotheses. Here, we present the results of a target, multi‐locus phylogenetic analysis, using mitochondrial (cox1, 16s and 12s) and nuclear genes (h3, 28s and 18s), of the most exhaustive taxonomic sample within Dysderidae (104 spp.) to date and across related families (Synspermiata) (83 spp.). We estimate divergence times using a combination of fossil and biogeographic node calibrations and use this timeline to identify shifts in diversification rates. Our results support the monophyly of the Dysderidae subfamilies Rhodinae and Dysderinae but reject Harpacteinae as currently defined. Moreover, the clades recovered within Harpacteinae do not support its current taxonomy. The origin of the family most likely post‐dated the break‐up of Pangea, and cave colonization may be older than previously considered. After correcting for the taxonomic artefacts, we identified a significant shift in diversification rates at the base of the genus Dysdera. Although the unique coexistence of specialist and generalist diets within the lineage could be suggested as the potential driver for the rate acceleration, further quantitative analyses would be necessary to test this hypothesis. [ABSTRACT FROM AUTHOR]

Aim: Quantifying the relative contribution of environmental filtering versus limiting similarity in shaping communities is challenging because these processes often act simultaneously and their effect is scale‐dependent. Focusing on caves, island‐like natural laboratories with limited environmental variability and species diversity, we tested: (i) the relative contribution of environmental filtering and limiting similarity in determining community assembly in caves; (ii) how the relative contribution of these driving forces changes along environmental gradients. Location: Europe. Time period: Present. Major taxa studied: Subterranean spiders. Methods: We used data on distribution and traits for European cave spiders (n = 475 communities). We estimated the trait space of each community using probabilistic hypervolumes, and obtained estimations of functional richness independent of the species richness of each community via null modelling. We model functional diversity change along environmental gradients using generalized dissimilarity modelling. Results: Sixty‐three percent of subterranean spider communities exhibited a prevalence of trait underdispersion. However, most communities displayed trait dispersion that did not depart significantly from random, suggesting that environmental filtering and limiting similarity were both exerting equally weak or strong, yet opposing influences. Overdispersed communities were primarily concentrated in southern latitudes, particularly in the Dinaric karst, where there is greater subterranean habitat availability. Pairwise comparisons of functional richness across caves revealed these effects to be strongly scale‐dependent, largely varying across gradients of cave development, elevation, precipitation, entrance size and annual temperature range. Conversely, geographical distance weakly affected trait composition, suggesting convergence in traits among communities that are far apart. Main conclusions: Even systems with stringent environmental conditions maintain the potential for trait differentiation, especially in areas of greater habitat availability. Yet, the relative influence of environmental filtering and limiting similarity change with scale, along clear environmental gradients. The interplay of these processes may explain the assembly of species‐poor subterranean communities displaying high functional specialization. [ABSTRACT FROM AUTHOR]

This study presents the first molecular phylogenetic analysis of the Clinocerinae, challenging the traditionally accepted monophyly of this subfamily. DNA was extracted from fresh and museum specimens representing all biogeographical regions. Maximum likelihood (ML) and Bayesian inference (BI) phylogenetic analyses were performed based on sequences from two mitochondrial genes, cytochrome c oxidase subunit I (COI) and cytochrome β, and three nuclear genes, carbomoylphosphate synthase domain of rudimentary, elongation factor‐1α and isocitrate dehydrogenase. Through molecular data and morphological examination, our results reveal a division within Clinocerinae, distinguishing ‘typical’ or Clinocerinae (s.s.) from several genera, specifically Afroclinocera Sinclair, Asymphyloptera Collin and Proagomyia Collin, possibly lending support for a reclassification of these genera outside Clinocerinae. Bergenstammia Mik is proposed as a junior synonym of Phaeobalia Mik, syn. n., and the following new combinations are recognized: Phaeobalia albanica (Wagner) comb. n., Phaeobalia aurinae (Pusch & Wagner) comb. n., Phaeobalia carniolica (Horvat) comb. n., Phaeobalia frigida (Vaillant) comb. n., Phaeobalia glacialis (Palaczyk & Słowińska) comb. n., Phaeobalia multiseta (Strobl) comb. n., Phaeobalia nudimana (Vaillant) comb. n., Phaeobalia nudipes (Loew) comb. n., Phaeobalia pulla (Vaillant & Wagner) comb. n., Phaeobalia pyrenaica (Vaillant & Vinçon) comb. n., Phaeobalia slovaca (Wagner) comb. n. and Phaeobalia thomasi (Vaillant & Vinçon) comb. n. Re‐evaluation of the genus Roederiodes resulted in the following new combinations: Clinocerella macedonicus (Wagner & Horvat) comb. n. and Clinocerella montenegrinus (Wagner & Horvat) comb. n. The origins of Clinocerinae (s.s.) are traced back to the Holarctic region, Laurasian origin, with a likely complex history of dispersal events into the Southern Hemisphere. Based on current knowledge, the greatest generic and species richness is confined to the Palaearctic Region. These findings provide valuable insights into the evolutionary relationships and distribution patterns of Clinocerinae (s.s.), challenging existing taxonomic classifications and shedding light on their historical biogeography. [ABSTRACT FROM AUTHOR]

Geometric regularity of spider webs has been intensively studied in orb‐weaving spiders, although it is not exclusive of orb weavers. Here, we document the geometrically regular, repetitive elements in the webs of the non‐orb‐weaving groups Leptonetidae and Telemidae for the first time. Similar to orb weavers, we found areas with regularly spaced parallel lines in the webs of Calileptoneta helferi, Sulcia sp., and cf. Pinelema sp. Furthermore, we provide a detailed account of the regular webs of Ochyrocera (Ochyroceratidae). The sections of the web with regularly disposed parallel lines are built as U‐shaped modules reminiscent of orb webs. It has been suggested that the regularly spaced parallel lines in the webs of Ochyroceratidae and Psilodercidae may be produced in a single sweep of their posterior lateral spinnerets, which have regularly spaced aciniform gland spigots, perhaps involving expansion of the spinnerets. To test this hypothesis, we compared the spacing between parallel lines with the spacing between spigots, searched for expansible membranes in the spinnerets, and examined the junctions of regularly spaced lines. The distance between parallel lines was 10–20 times the distance between spigots, and we found no expansible membranes, and the intersection of parallel lines are cemented, which opposes the single sweep hypothesis. Furthermore, we found cues of viscid silk in the parallel lines of the psilodercid Althepus and broadened piriform gland spigots that may be responsible of its production. Finally, we evaluated the presence or absence of geometrically regular web elements across the spider tree of life. We found reports of regular webs in 31 spider families, including 20 families that are not orb weavers and hypothesize that the two basic aspects of regularity (parallel lines spaced at regular intervals, and radial lines spaced at regular angles) probably appeared many times in the evolution of spiders. [ABSTRACT FROM AUTHOR]

Aim: To disentangle the role of evolutionary history, competition and environmental filtering in driving the niche evolution of four closely related subterranean spiders, with the overarching goal of obtaining a mechanistic description of the factors that determine species' realized distribution in simplified ecological settings. Location: Dinaric karst, Balkans, Europe. Taxon: Dysderidae spiders (Stalita taenaria, S. pretneri, S. hadzii and Parastalita stygia). Methods: We resolved phylogenetic relationships among species and modelled each species' distribution using a set of climatic and habitat variables. We explored the climatic niche differentiation among species with n‐dimensional hypervolumes and shifts in their trophic niche using morphological traits related to feeding specialization. Results: Climate was the primary abiotic factor explaining our species' distributions, while karstic and soil features were less important. Generally, there was a high niche overlap among species, reflecting their phylogenetic relatedness, but on a finer scale, niche shifts explained the realized distribution patterns. Trophic interaction was another important factor influencing species distributions – the non‐overlapping distributions of three morphologically indistinguishable Stalita species is seemingly the outcome of competitive exclusion dynamics. The distribution of the fourth species, Parastalita stygia, overlaps with that of the other species, with several instances of coexistence within caves. As inferred from the morphology of the mouthparts, the mechanism that minimizes interspecific competition is the shift in the trophic niche of P. stygia towards a more specialized diet. Main conclusions: We showed that similarity in niches only partly correlated with the phylogenetic distance among species, and that overlaps in species distributions are possible only when a parallel shift in diet occurs. Our work emphasized how even simplified environments still maintain the potential for diversification via niche differentiation. Ultimately, we provide an ecological explanation for the diversification of life in an important hotspot of subterranean diversity. [ABSTRACT FROM AUTHOR]

One of the most striking features of obligate subterranean species is their narrow distribution ranges. These prevail not only at specific, but often also at generic level. However, some subterranean genera have continental scale and disjunct distribution, which challenges their monophyly and questions the scenarios of their origin and colonization. In our study, we investigated the subterranean collembolan genus Verhoeffiella, currently known from five remote karst regions of Europe. Four nuclear and one mitochondrial genes were assembled to reveal the evolutionary history of the genus. We tested the monophyly of the genus, explored its relationship with putative surface relatives, and its temporal patterns of molecular diversification. The phylogeny revealed a complex relationship of Verhoeffiella with surface species Heteromurus nitidus and partially disentangled the biogeographical question of its disjunct distribution. Further on, several lineages of Verhoeffiella were recognized in the Dinarides, showing highly underestimated diversity and, compared with the number of described species, a sevenfold increase in the number of MOTUs. The radiation is relatively recent, with the events triggering the diversification linked to the Messinian salinity crisis and Pleistocene climatic shifts. The combination of this extensive subterranean radiation and close evolutionary links with epigean relatives makes Verhoeffiella an exceptional case within the subterranean fauna of temperate areas, which significantly contributes to our understanding of subterranean colonization and diversification patterns. [ABSTRACT FROM AUTHOR]