Data from: Population admixture and high larval viability among urban toads

In terms of evolutionary biology, a population admixture of more than two
distinct lineages may lead to strengthened genetic variation through
hybridization. However, a population admixture arising from artificial
secondary contact poses significant problems in conservation biology. In
urban Tokyo, a population admixture has emerged from two lineages of
Japanese common toad: native Bufo japonicus formosus and nonnative B.
japonicus japonicus, of which the latter was introduced in the early 20th
century. To evaluate the degree of genetic disturbance in the admixed
population of these two subspecies, we analyzed genotypes of toads
distributed within and outside Tokyo by assessing mtDNA and seven
microsatellite loci. We found that the introduced B. japonicus japonicus
genotype dominates six local populations in the Tokyo admixture zone and
was clearly derived from past introgressive hybridization between the two
subspecies. These observations were supported by morphological
assessments. Furthermore, the average larval survival rate in Tokyo was
significantly higher than that outside Tokyo, suggesting that the
temporary contribution of introduced toads occurred through introgression.
The fitness of toads in urban Tokyo may thus be increasing with the
assistance of nonnative individuals.