A multi-layered approach uncovers overlooked taxonomic and physiological diversity in Alpine subterranean spiders (Araneae: Linyphiidae: Troglohyphantes)

Abstract

The integration of multiple lines of evidence in the delimitation of taxa is becoming the gold standard in modern taxonomy and systematics. However, multi-layered taxonomy is still incipient when it comes to species description within a mega-diverse group of organisms (e.g. arthropods), especially those inhabiting secluded environments such as caves. This may represent a significant shortcoming, because species in subterranean habitats generally show deep convergence in their somatic traits, perplexing our ability to delimit species by traditional approaches. The genus Troglohyphantes Joseph, 1882 (Araneae: Linyphiidae) is presently known to include 129 species and 5 subspecies, all of which are primarily distributed in subterranean habitats of the European mountain ranges. Recent studies on Italian alpine species covered taxonomy and faunistic, biogeography and ecology. However, our knowledge about the actual species diversity of Troglohyphantes spiders is far from complete, and it is expected that significant levels of overlooked diversity might exist within the genus. In this work, we combined morphological data with target gene molecular data, functional trait analysis and thermal physiology to explore overlooked diversity in Troglohyphantes vignai auct., a species of subterranean spider in the Western Italian Alps with an apparently broader distribution than its congeners. Our approach proved effective in uncovering overlooked diversity and further supporting the split of T. vignai auct. into three distinct species whose distribution ranges how striking resemblances with that of other subterranean spiders. We here describe the new species and discuss their origins in light of their geographical vicariance, niche convergence, thermal ecology and divergence time.