Gates Katie, Sandoval-Castillo Jonathan, Beaman Julian E, da Silva Karen Burke, Saltré Frédérik, Belov Katherine, Hogg Carolyn J, Bradshaw Corey J A, Beheregaray Luciano B
Molecular Ecology Laboratory, College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia.
Global Ecology Partuyarta Ngadluku Wardli Kuu, College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia.
Mol Ecol. 2025 Oct;34(20):e70097. doi: 10.1111/mec.70097. Epub 2025 Sep 13.
The persistence of many threatened species depends on isolated habitat patches such as conservation parks, fenced reserves, and islands. While these 'conservation arks' provide refuge from many contemporary threats, they can also pose risks of genetic diversity loss and inbreeding depression, further exacerbating extinction risk. A pertinent example is the Kangaroo Island koala population in South Australia that originated from a few translocated founding individuals in the 1920s but now sustains a large population with a low prevalence of infectious disease. We investigated the extent and consequences of founder effects on genomic diversity, inbreeding, and adaptive potential in Kangaroo Island koalas by comparing them with mainland Australian populations using high-coverage whole genomes. Our findings support sharp, recent declines in effective population sizes (N) in both mainland and Kangaroo Island populations. However, Kangaroo Island koalas had much lower individual and population-level diversity. Together with longer and more numerous runs of homozygosity and an increased proportion of homozygous genetic load, these results support the hypothesis that a severe bottleneck has contributed to inbreeding and maladaptation in Kangaroo Island koalas. While Kangaroo Island has the potential to conserve a viable population of koalas, we recommend genetic rescue to restore diversity and mitigate inbreeding depression in this isolated population. Our results emphasise the need for longitudinal genomic monitoring and genetic management to maintain long-term viability and resilience in potential conservation arks. Understanding the demographic history of such populations will help inform future conservation aimed at preventing genetic erosion and preserving biodiversity.
许多濒危物种的存续依赖于孤立的栖息地斑块，如自然保护公园、围栏保护区和岛屿。虽然这些“保护方舟”为它们提供了躲避诸多当代威胁的庇护所，但也可能带来遗传多样性丧失和近交衰退的风险，进一步加剧灭绝风险。一个相关的例子是南澳大利亚袋鼠岛的考拉种群，该种群起源于20世纪20年代少数几只被迁移过去的奠基个体，如今维持着数量众多且传染病患病率较低的种群。我们通过使用高覆盖度全基因组将袋鼠岛考拉与澳大利亚大陆种群进行比较，研究了奠基者效应对袋鼠岛考拉基因组多样性、近交和适应潜力的影响程度及后果。我们的研究结果支持了近期澳大利亚大陆和袋鼠岛种群的有效种群大小（N）都急剧下降的观点。然而，袋鼠岛考拉的个体和种群水平多样性要低得多。再加上更长、更多的纯合子片段以及纯合遗传负荷比例的增加，这些结果支持了这样一种假设，即严重的瓶颈效应导致了袋鼠岛考拉的近交和适应不良。虽然袋鼠岛有潜力保护一个可行的考拉种群，但我们建议进行基因拯救，以恢复该孤立种群的多样性并减轻近交衰退。我们的研究结果强调了进行纵向基因组监测和遗传管理以维持潜在保护方舟中种群的长期生存能力和恢复力的必要性。了解这些种群的种群历史将有助于为未来旨在防止遗传侵蚀和保护生物多样性的保护工作提供信息。
