Persistence of asexuality through mixed reproduction in Eucypris virens (Crustacea, Ostracoda)

The ostracod species Eucypris virens exhibits geographical parthenogenesis, with rare sexual populations in southern Europe and widespread asexual pop ulations elsewhere. DNA sequence data from the nuclear ITS1 and mitochondri al COI regions have been used to estimate genetic variabilities and reconst ruct phylogenies. The observed divergence was exceptionally high, with intr aspecific maxima of 10.3% (ITS1) and 20.9% (COI) among European lineages, l evels reported for interspecific comparisons of other taxa. Phylogenetic re constructions reveal multiple origins of asexual clones from sexual populat ions. However, we argue that such data can only provide a lower limit on th e number of origins of asexual reproduction, and an upper limit on the age of asexual lineages. Congruence between gene trees for different loci can p rovide support for the inference of long-term apomictic reproduction. Nucle ar and mitochondrial data differ in their placement of some asexual clones, possibly indicating that genetic exchange has taken place between sexual a nd asexual lineages. Such intraspecific hybridization is one route to combi ne the benefits of both reproductive modes, and it might explain how asexua lity managed to persist in E. virens even in long, evolutionary terms.