Lineage distribution of the Gammarus fossarum species complex (Amphipoda) across Bohemian Massif and Western Carpathians

Amphipods are an important component of temperate permanent freshwater macrozoobenthos. They have poor dispersal abilities, lack dormant stages, and their phylogeographies often reflect old historical processes. The genus Gammarus itself includes more than 200 described species spread in the Palearctic region. Many of the taxa previously described are, in fact, diversified species complexes, which is case of our most common Gammarus (G. fossarum). We have studied their diversity on the transect across the Bohemian Massif and the Western Carpathians, which form a significant biogeographical boundary for a number of other organisms. We tested whether the border between these areas is reflected in the phylogeography of G. fossarum as a representative of permanent aquatic fauna. Analysis of two mitochondrial markers revealed the presence of eight divergent G. fossarum lineages, which also differed in the nuclear genome. All eight lineages were found in the Western Carpathians, while the Czech Massif is inhabited only by two. The microendemic areas of some lineages and the occurrence of two apparently basal lineages of this complex, which were not found in southern regions, support the hypothesis that these amphipods survived Pleistocene glacial cycles even in West Carpathian refuges. We assume that..