Genetic structure and new occurrence records of the iconic Tasmanian mountain shrimp Anaspides tasmaniae (Thomson, 1893) (Anaspidesidae : Anaspidacea) reveal relictual distribution in southern Tasmania

Abstract

The iconic ‘mountain shrimps’ of the genus Anaspides Thomson, 1894, are endemic to Tasmania, inhabiting various freshwater habitats such as mountain tarns and creeks, as well as streams inside caves. They are often labelled as ‘living fossils’ because of their close resemblance to their Triassic relatives. Prior to 2015, only two species were recognised but recent studies have uncovered a total of at least seven species. The type species of Anaspides, A. tasmaniae (Thomson, 1893), was previously believed to occur throughout Tasmania, but following a review in 2016, this species was confirmed only from a small range on the east and south-east side of Mt Wellington, with Anaspides from other parts of Tasmania referable to other species. We herein provide a detailed assessment of the distribution and genetic structure of A. tasmaniae based on extensive field surveys throughout the ranges of all species of Anaspides. The distribution of A. tasmaniae is extended to include four separate localities in and around the Mt Field National Park, 50 km north-west of Mt Wellington. The recovered genetic structure of A. tasmaniae based on 48 specimens indicates that the disjunct distribution is unlikely to be the result of artificial translocation but, instead, probably reflects postglacial relictualisation of a formerly continuous range present during Pleistocene glacial maxima. Of particular interest is the record of syntopy in Anaspides, observed at the entrance of Khazad Dum cave, where both A. tasmaniae and A. swaini inhabit the inflow stream.