Data from: Density-dependent unidirectional hybridization between the Japanese pond turtle, Mauremys japonica and the exotic Reeves’ pond turtle, Mauremys reevesii in Japan, inferred from molecular and morphological analyses

Hybridisation between the indigenous Japanese pond turtle, Mauremys
japonica, and the exotic Reeves’ pond turtle, Mauremys reevesii, is
widespread in Japan. In this study, we examined this hybridisation using
an analysis of mtDNA and 11 microsatellite markers (MS) combined with
morphometry. In a Bayesian clustering analysis of MS, the admixture of two
clusters equivalent to the two species was detected in the Seto Inland Sea
and Ise Bay regions. While mtDNA showed reciprocal hybridisation between
the two species, their hybrids tended to possess the mtDNA of the rarer
species at each locality. Contrary to preceding studies, F2/later
generations outnumbered F1 generations. In addition, the admixture of two
mtDNA lineages (Chinese and Korean) of M. reevesii was widely observed in
all regions, together with the range expansion of the recently introduced
Chinese lineage. A significant correlation was observed between plastron
morph and assignment probability of MS, showing that plastron morphology
reflects the degree of introgression by M. reevesii in M. japonica. This
finding means that the reproductive interference of the dominant species
on a rarer species is a major factor driving the hybridisation of the two
Mauremys species. In addition, the range expansion of the Chinese lineage
of M. reevesii appears to enhance the introgression by M. reevesii in M.
japonica.