Revisiting European and Asian Diamesa species (Diptera: Chironomidae: Diamesinae): morphological and molecular insights

Diamesa is a cold-adapted genus of Diptera: Chironomidae colonizing cold freshwaters of the Northern Hemisphere and East Africa. Global warming and glacier shrinkage are threatening their survival. In this work, we aimed to provide new insights into taxonomical gaps and phylogeny of Diamesa species from the Pyrenees, Alps, and Karakorum mountains to understand the colonization processes better and have a more accurate count of the number of endangered species. An incongruence between morphological identification and DNA barcoding (COI) was highlighted, suggesting the need for other approaches combined to estimate genetic distance. We reconstructed the phylogeny of the Palaearctic, using molecular data from two nuclear (CADI and CADIV) and three mitochondrial (COI and COII and 16S) genes. We emphasized that: (i) the Diamesa steinboecki group shares with the common ancestor of the other Diamesa species a strong cold adaptation; (ii) the European and Asian species belonging to the steinboecki group separated from each other during the Miocene (~15 Mya); and (iii) the major diversification of species in the Alps occurred during the Plio-Pleistocene epochs, mainly during the alternation of glacial and interglacial periods. This confirms the strong relationship between species evolution and climate change.