Francesco Ballarin (1, 2) & Shuqiang Li (1)
(1) Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing 100101, P. R. China
(2) Sezione di Zoologia, Museo Civico di Storia Naturale di Verona, Lungadige Porta Vittoria, 9, I-37129 – Verona, Italy
Nesticidae is a relatively small family of troglophilic spiders widely distributed along temperate, subtropical and tropical areas of the world and currently including 15 genera and 278 species (World Spider Catalog, 2018). Traditionally the family has been considered rather uniform since its establishment by Simon in 1894, with the wide majority of the North American, European and Asian species previously included in the genus Nesticus. Only recently, new studies carried out using both morphological characters and molecular analysis have revealed a much wider diversity of genera and species, allowing a consistent revision of the family. Here we illustrate the current phylogenetic status of Nesticidae inferred on the base of new molecular studies and we discuss the primary role of ancient climatic events in shaping the evolutionary history of these spiders. To accomplish this goal we analyzed the sequences of more than 120 nesticid species, mostly from Europe and Asia. We selected two mitochondrial (COI & 16S) and four nuclear gene fragments (18S, 28S, H3 & Actin5c) for a total of more than 6000bp to reconstruct, and subsequently time-calibrate, a robust phylogenetic tree of nesticid spiders. Our preliminary results show that the family Nesticidae, as intended so far, could be polyphyletic with the genera Gaucelmus, Hamus and Nescina possibly belonging to different spider families. We confirm the ancient age of the family dating its origin in Upper Cretaceous and we identify three main evolutionary lineages within the Nesticidae sensu stricto. Accordingly to our preliminary analysis, the climatic and geological events occurred in Eurasia along the second half of the Eocene Epoch (~41–34 Ma) deeply shaped the phylogeny and distribution of Nesticidae, causing extinctions and promoting allopatric speciation between the close-related European and Asian clades. More recently, during the last 15 Ma, a faster diversification rate can be recorded involving a possibly explosive radiation in the taxa distributed in the Carpathian Mountains and in Japan.
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Francesco Ballarin & Shuqiang Li