Glacial and postglacial species divergence and dispersal of European trickle midges (Diptera: Thaumaleidae)

Pleistocene glaciations have greatly influenced the current distribution and diversity of aquatic and terrestrial species in Europe. We studied the phylogeography and the genetic structure of European trickle midges (Diptera: Thaumaleidae). This family is restricted to hygropetric zones with the genera Thaumalea, Protothaumalea and Androposopa occuring in Europe, including both microendemisms and species widely distributed across the continent. A 658-bp fragment of the mitochondrial CO1 and a 563-bp fragment of the nuclear Wingless-gene from 56 individuals belonging to 14 species were sequenced and analysed. Androposopa is monophyletic and sister group to a broad Thaumalea clade which includes Protothaumalea. All species for which multiple populations were available are monophyletic, while the previously suggested hypothesis of species groups within Thaumalea is not supported. To understand the influence of glacial dynamics on Thaumaleidae evolution, we investigate four different scenarios for species divergences, testing different periods for within-species population splits. The results suggest different evolutionary histories for different species. For Thaumalea testacea, we found evidence for survival in multiple Alpine refugia throughout the glacial maxima. On the other hand, T. bezzii seems to have dispersed into Central Europe from the East Mediterranean area after the last glaciation. For the Faroe Islands populations of T. Veralli, dispersal could have happened by air currents from Europe rather than by anthropogenic transport. Overall, our results show a wide range of dispersal patterns within an otherwise uniform group of organisms, opening new avenues for further studies in phylogeography and speciation.