Extra-Mediterranean glacial refugia and range dynamics in a groundwater amphipod species, Niphargus fontanus Spence Bate, 1859, in western Central Europe

Abstract

The biogeography, taxonomy and systematics of ground water organisms is still poorly understood. This is partly due to the difficult accessibility of the habitats and the expert knowledge required for identification. Nevertheless, due to the large distribution range and limited dispersal possibilities of amphipods such as the genus Niphargus, important insights can be gained into biogeographical patterns and evolutionary processes in subterranean ecosystems. Niphargus is the most species-rich genus of freshwater amphipods worldwide and holds great potential for cryptic species whose identification is important for the reconstruction of biogeographic patterns and events. Therefore, we assessed the genetic patterns of Niphargus fontanus Spence Bate, 1859 (Amphipoda: Niphargidae). We sampled the species all over its current distribution and sequenced one mitochondrial and three nuclear gene fragments. We discovered that most records from France were probably misidentifications, and that the species does not occur in central and southern France. Nevertheless, the distribution area extends from Wales to Bavaria, which could make it one of the largest distribution areas within the genus. Compared with other Niphargus, the genetic diversity and differentiation of N. fontanus is low and most likely evolved since the mid-Pleistocene Transition, but reflects a clear phylogeographic pattern with about 13 genetic lineages. These apparently stand for a number of extra-Mediterranean glacial refugia from which postglacial expansion was low to moderate. However, few cases of disjunction within these genetic lineages exist, most likely resulting from rapid expansions along river Rhine which otherwise mostly acted as a dispersal barrier.