Genetic diversity and mixed reproduction in Eucypris virens (Crustacea: Ostracoda)

Abstract

We report data on the coexistence of apomictic and amphimictic lineages of Eucypris virens within the same pond and discuss the role of intraspecific hybridation as a source of genetic variability. We describe the genetic structure of 36 populations of E. virens from Europe. Most (28) populations were made up of putative parthenogenetic females, in 8 populations from Spain and Sicily we found males. Using three polymorphic allozyme markers (MPI, PGM and GPI) we described at least 214 different multilocus genotypes (clones) in a total of 1151 analysed specimens and confirmed that parthenogenetic reproduction is apomictic. Most multilocus genotypes, 74 %, were limited to a single population indicating the absence of a single widespread 'clone'. In E. virens, genetic diversity was not affected by latitudinal dine or reproductive mode and was probably the result of several processes. Apomictic lineages were the likely result of at least two independent transitions from different sexual ancestors located in Southern Europe, in Central Spain and in Sicily. Transitions probably happened after the last glaciation. We found sympatric amphimictic and apomictic females in Extremadura (Western Spain) and reported evidence of gene flow between different lineages (intraspecific hybridation). Further genetic differentiation within and among populations reflects time of divergence and mutation accumulation. We found putative polyploid multilocus genotypes in all populations with males, further support for the coexistence of lineages with different reproductive modes. The presence of polyploid genotypes (14 %) is probably underestimated and this limits our ability to assess the role of hybridisation as a major route to parthenogenesis.