Limited long-distance dispersal success in a Western European fairy shrimp evidenced by nuclear and mitochondrial lineage structuring

nostraca are known by their ability for long-distance dispersal, but the existence in several spe-cies of deep, geographically structured mtDNA lineages suggests their populations are subjectedto allopatric differentiation, isolation, and prevalence of local scale dispersion.Tanymastix stagna-lisis one of the most widespread species of Anostraca and previous studies revealed an uncleargeographical pattern of mtDNA genetic diversity. Here, we analyze populations from the Iberianand Italian Peninsulas, Central Europe, and Scandinavia, with the aim to characterize the patternsof genetic diversity in a spatio-temporal framework using mtDNA and nuclear markers to test geneflow among close populations. For these aims we built a time-calibrated phylogeny and carried outBayesian phylogeographic analyses using a continuous diffusion model. Our results indicated thatT. stagnalispresents a deeply structured genetic diversity, including 7 ancient lineages, some ofthem even predating the Pleistocene. The Iberian Peninsula harbors high diversity of lineages, withstrong isolation and recent absence of gene flow between populations. Dispersal at local scaleseems to be the prevailing dispersal mode ofT. stagnalis, which exhibits a pattern of isolation-by-distance in the Iberian Peninsula. We remark the vulnerability of most of these lineages, giventhe limited known geographic distribution of some of them, and the high risk of losing importantevolutionary potential for the species.This work was supported by the Project Grant CGL2015-66571-P (MINECO/FEDER) of Spain