Population Genetic Structure Analysis Reveals Decreased but Moderate Diversity for the Oriental Fire-Bellied Toad Introduced to Beijing after 90 Years of Independent Evolution

SIMPLE SUMMARY: Habitat isolation and loss are significant factors that lead to the decline of wildlife populations worldwide, and habitat loss further leads to the shrinkage of populations, which increases the risk of inbreeding and the genetic decline of the populations. To explore the independent evolutionary characteristics of different populations, this study analyzed the genetic disparity of the introduced oriental fire-bellied toad in Beijing from a source population in Shandong Province. The results show that, despite originating from a small artificially introduced population, the toads in the Beijing region have maintained a moderate genetic diversity after 90 years of independent evolution, indicating that this species has a high capacity for survival and adaptation. ABSTRACT: Detailed molecular genetic research on amphibian populations has a significant role in understanding the genetic adaptability to local environments. The oriental fire-bellied toads (Bombina orientalis) were artificially introduced to Beijing from Shandong Province in 1927, and since then, this separated population went through an independent evolution. To explore the differentiation of the introduced population with its original population, this study analyzed the genetic structure of the oriental fire-bellied toad, based on the mitochondrial genome control region and six microsatellite sites. The results showed that the haplotype diversity and nucleotide diversity of the mitochondrial D-loop region partial sequences of the Beijing Botanical Garden population and the Baiwangshan population were lower than those of the Shangdong Kunyushan population. Microsatellite marker analysis also showed that the observed heterozygosity and expected heterozygosity of the Beijing populations were lower than those of the Kunyushan population. The phylogenetic trees and network diagrams of haplotypes indicated that the three populations were not genetically separated. However, the structure analysis showed a genetic differentiation and categorized the sampling individuals into Beijing and Shandong genetic clusters, which indicated a tendency for isolated evolution in the Beijing population. Although the Beijing populations showed a decline in genetic diversity, it was still at a moderate level, which could maintain the survival of the population. Thus, there is no need to reintroduce new individuals from the Kunyushan source population.