Molecular taxonomy, phylogeny and biogeography of the Niphargus tatrensis species complex (Amphipoda, Niphargidae) in Austria

Abstract

The Niphargus tatrensis species complex, entirely subterranean, has a wide distribution range extending from Southern Poland to Austria and Slovenia. Because of its large and confusing morphological variability, it was subdivided into several ‘forms’, four of which described from Austrian caves. To shed light on this chaotic situation, we sampled the type localities of all described species and forms in the complex, as well as additional sites in Austria, and used nuclear (28S, ITS) and mtDNA (COI) sequences to revise its taxonomy. Phylogenetic analysis confirmed that the Niphargus tatrensis species complex is monophyletic. Applying four species delimitation methods to the COI dataset converged on the presence of four species in Austria; by contrast, the same methods applied to ITS concurred with a haploweb analysis of this marker in distinguishing only three species in the country. Reconstruction of ancestral ranges suggested that the Austrian clade originated in Eastern Europe. Bayesian biogeographical analyses revealed a complex history of lineage divergence and secondary contact during the Pleistocene climatic fluctuations, possibly responsible for the higher variability of COI in comparison with ITS. Based on the above, we conclude that only three valid species are present in Austria: considering all described forms as subspecies, two of them are elevated to species rank whereas one new species is formally described and illustrated.