Abstract
Population fragmentation is one of the most concerning consequences of habitat fragmentation, as small and isolated populations suffer increased genetic drift and inbreeding. However, the extent to which habitat fragmentation leads to population fragmentation depends not only on the landscape structure, but also on the response of organisms to it. This behavioral component makes it difficult to detect population fragmentation even if the habitat is fragmented, unless appropriate tools are used. In this study, we used a molecular approach to evaluate if Dahl’s toad-headed turtle (Mesoclemmys dahli) population was fragmented, given that it occurs in a very restricted area within the most degraded biome of Colombia, the tropical dry forest. We developed a panel of 15 microsatellite loci in order to perform the first genetic assessment of M. dahli across its complete geographic range. We found that M. dahli has significant genetic structure with at least four subpopulations, with surprisingly moderate to high levels of genetic diversity. Despite high levels of genetic diversity, subpopulations are very small (effective population sizes < 50) and isolated, with little to no contemporary gene flow among them. As a consequence, mating among related individuals has been occurring, and all four populations are showing high degrees of inbreeding. To counteract this threat, we recommend an urgent genetic rescue strategy accompanied by habitat restoration, and advocate for a new conservation status assessment, not based on geographic range, but on adult population size and level of fragmentation.
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Photograph: M. Vargas-Ramírez
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Acknowledgements
We thank field researchers Luis Eduardo Rojas, Jhon Fredy Gaitán and Oscar Díaz for their invaluable help in sample collection. We thank the laboratory technicians Sonia Quintanilla and Mauricio Buitrago. This project was funded by Ecopetrol S.A. as part of their Tropical Dry Forest Initiative in Colombia. We thank the Wildlife Conservation Society, Turtle Survival Alliance, Fundación Mario Santo Domingo, and Universidad de los Andes for technical and financial support. Sampling and access to genetic resources allowed by “Contrato de acceso a recursos genéticos para investigación científica sin interés comercial No. 65, signed between the Ministerio de Ambiente y Desarrollo Sostenible de Colombia and Mario Vargas-Ramírez.
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Gallego-García, N., Vargas-Ramírez, M., Forero-Medina, G. et al. Genetic evidence of fragmented populations and inbreeding in the Colombian endemic Dahl’s toad-headed turtle (Mesoclemmys dahli). Conserv Genet 19, 221–233 (2018). https://doi.org/10.1007/s10592-017-1021-z
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DOI: https://doi.org/10.1007/s10592-017-1021-z