Old Aegean palaeoevents driving the diversification of an endemic isopod species (Oniscidea, Trachelipodidae)

The Greek endemic isopod species Trachelipus aegaeus is distributed in Aegean islands and the adjacent coastal parts of the Greek mainland. Major palaeogeographic events of the Aegean archipelago, such as the formation of the mid-Aegean trench and the Messinian Salinity Crisis, have been often employed as major causal factors of evolutionary events and phylogeographic patterns exhibited by several taxa. Herein, we infer phylogenetic relationships among T. aegaeus populations using partial cytochrome oxidase subunit I (COI) and 16S rRNA sequences. Due to the poor preservation of the specimens, we propose a modified DNA extraction protocol, which returned highly positive results in terms of the quality of the total extracted DNA. We implement a calibrated molecular clock and path sampling analysis, using alternative palaeogeographic events and rates of substitution, to evaluate the biogeographic history of the species and to estimate the chronology of diversification events among its populations. Our results are clearly in favour of the scenario of the MAT triggering vicariance among most T. aegaus populations. Moreover, the large intraspecific genetic divergence (0–19% for COI and 0–20.3% for the 16S rRNA) and the overall phylogeographic patterns depicted herein seem not to have been obscured by more recent palaeogeological events. A role of dispersal, probably human-aided, is assumed for certain ‘deviant’ cases.