Phylogeny and species diversity of Tasmanian mountain shrimps and their relatives (Crustacea, Anaspidesidae)

Anaspidacea is an enigmatic taxon within Malacostraca with uncertain phylogenetic affinities. One of the four families within Anaspidacea, the Anaspidesidae (representing in most respects the plesiomorphic conditions of the entire taxon), is endemic to Tasmania and shows a remarkable geographical and vertical distribution. Eleven species in three genera (Allanaspides, Anaspides and Paranaspides) are recognized to date, occurring in freshwater habitats such as lakes, rivers, streams, tarns and also in caves. We present the most detailed analyses to date of the phylogeny of Anaspidesidae including all eleven species based on molecular data (COI, 16S and 28S). In addition, the genetic differentiation within the morphologically recognized species is studied and a dating of speciation is given using a molecular clock approach (based on mt-DNA only). A special focus is on the multiple instances of immigration into the subterranean habitat. Most of the morphologically delineated species are recognized by molecular data. Significantly, however, in at least two cases, the molecular data suggest more species than so far described, but further molecular sampling from a wider range of localities is required. Our molecular divergence estimates suggest the anaspidesids are younger than previously thought. Rather than having Eocene origins, our results suggest Early Miocene origins with primary diversification in Miocene and Pliocene. Entry into subterranean habitats appears to have occurred in the Pleistocene rather than Tertiary. Thus, rather than being a defensive response to rising temperatures in the Tertiary, entry into caves in the Pleistocene may represent opportunistic expansion into new habitats created by the action of glacial meltwaters on existing karst formations. As a result, environmental changes during the Pleistocene appear to have prompted ecological expansion of Anaspides by “opening” new subterranean habitats leading to increased diversification in the group.