Population admixture and high larval viability among urban toads
Article first published online: 2 MAY 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 3, Issue 6, pages 1677–1691, June 2013
How to Cite
Ecology and Evolution 2013; 3(6): 1677–1691
- Issue published online: 12 JUN 2013
- Article first published online: 2 MAY 2013
- Manuscript Accepted: 25 MAR 2013
- Manuscript Revised: 22 MAR 2013
- Manuscript Received: 12 MAR 2013
- University of Tokyo
- Genetic disturbance;
- introgressive hybridization;
- population admixture;
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.