Abstract
Revealing patterns of genetic diversity and barriers for gene flow are key points for successful conservation in endangered species. Methods based on molecular markers are also often used to delineate conservation units such as evolutionary significant units and management units. Here we combine phylo-geographic analyses (based on mtDNA) with population and landscape genetic analyses (based on microsatellites) for the endangered yellow-bellied toad Bombina variegata over a wide distribution range in Germany. Our analyses show that two genetic clusters are present in the study area, a northern and a southern/central one, but that these clusters are not deeply divergent. The genetic data suggest high fragmentation among toad occurrences and consequently low genetic diversity. Genetic diversity and genetic connectivity showed a negative relationship with road densities and urban areas surrounding toad occurrences, indicating that these landscape features act as barriers to gene flow. To preserve a maximum of genetic diversity, we recommend considering both genetic clusters as management units, and to increase gene flow among toad occurrences with the aim of restoring and protecting functional meta-populations within each of the clusters. Several isolated populations with especially low genetic diversity and signs of inbreeding need particular short-term conservation attention to avoid extinction. We also recommend to allow natural gene flow between both clusters but not to use individuals from one cluster for translocation or reintroduction into the other. Our results underscore the utility of molecular tools for species conservation, highlight outcomes of habitat fragmentation onto the genetic structure of an endangered amphibian and reveal particularly threatened populations in need for urgent conservation efforts.
Highlights
Despite conservation efforts, biodiversity of vertebrates is declining worldwide with more than a fifth of species classified as threatened (Hoffmann et al 2010)
At Cytb three haplotypes were present in 73 sequences from 46 localities with Forbach and Heppenheim showing unique haplotypes (For12, Hes13) besides the main one; at Cytochrome oxidase I (COI) two haplotypes were found in 17 sequences from 17 localities, where Brander Wald presented a unique haplotype (Bra34); nicotinamide adenine dinucleotide dehydrogenase subunit 4 (ND4) exhibited only one haplotype in 20 sequences from 19 localities
When the Cytb haplotypes were compared with other European sequences of B. variagata and B. bombina, phylogenetic analysis (Neighbor joining and maximum likelihood trees) results showed that all analyzed samples belonging to Germany were included into the Balkano-Western clade (Fig. 2)
Summary
Biodiversity of vertebrates is declining worldwide with more than a fifth of species classified as threatened (Hoffmann et al 2010). Factors that can influence population genetics of amphibians include both natural (e.g., slope, vegetative land cover; Mims et al 2015; Winiarski et al 2020) as well as anthropogenic features (e.g., roads, urban areas; Goldberg and Waits 2010; McKee et al 2017). Understanding such landscape impacts on genetic diversity and structure is important for identifying populations facing greatest risks of genetic depletion due to habitat destruction, and for developing optimal conservation strategies
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