The Proasellus (Crustacea, Isopoda) species group, endemic to the Balkan Lake Ohrid: a case of ecological diversification?

Abstract

Phylogenetic relationships and divergence times of the endemic Proasellus species group from the relict Lake Ohrid were examined using mitochondrial COI gene sequences. This group is composed of two divergent, well-supported reciprocally monophyletic clades. The topology of the phylogenetic tree, however, does not reflect the present morphology-based classification, especially in positioning P. remyi f. nudus outside the rest of P. remyi forms and separating P. arnautovici elongatus from P. arnautovici arnautovici. The results of the present study appear to be not fully consistent with the hypothesis of adaptive diversification driven by ecologically different environments. The study provides insight into speed and mode of morphological and molecular evolution in aquatic isopods, and it presents one of the first arguments for rapid diversification in Lake Ohrid.