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Phylogeography of Dinaric Drusus (Trichoptera, Limnephilidae) endemics: identification of the processes underlying high diversity and endemism in the Balkans

The impact of Pleistocene climatic changes on the biogeography of the European freshwater fauna is still far less understood than for terrestrial taxa. Similarly, the processes in the refugial regions, especially in the Balkans, seem to be more complex than originally recognized. The Balkans is renowned for its high biodiversity and endemism, but data on the age and origin of its fauna, especially endemics, are limited. Caddisflies are one of the groups particularly rich in endemics in this area. Mitochondrial sequence data (COI and 16S genes) were used to study the population structure and phylogeography of the caddisfly Drusus croaticus and divergence of seven other Drusus species, mostly range restricted endemics of the Dinaric region of the Balkan Peninsula. Furthermore, phylogeography and population structure of D. croaticus were compared with those of Drusus discolor, a widespread European species with insular distribution. The divergence of D. croaticus populations in Croatia and allopatric Drusus species in Bosnia dated to the Pleistocene, showing the importance of this time period for the origin and diversification of Balkan endemic taxa. The divergence of more distantly related species dated to the late Miocene/early Pliocene. Very high population structure and genetic differentiation on a small geographical scale was recorded, suggesting that these species are very poor dispersers. The existence of allopatrically fragmented lineages in D. croaticus and the endemic Bosnian species is most likely the result of long-term isolation in multiple microrefugia, probably due to the specific habitat requirements and life history traits of Drusinae coupled with the topographic complexity and historical changes in geomorphology of the region.

allopatric fragmentation; caddisflies; glacial refugia; mitochondrial DNA; speciation

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