PDF(Pubmed)
Abstract：
Impact of climate change is expected to be especially noticeable at the edges of a species\' distribution, where they meet suboptimal habitat conditions. In Mauritania and Iberia, two genetically differentiated populations of harbor porpoises (Phocoena phocoena) form an ecotype adapted to local upwelling conditions and distinct from other ecotypes further north on the NE Atlantic continental shelf and in the Black Sea. By analyzing the evolution of mitochondrial genetic variation in the Iberian population between two temporal cohorts (1990-2002 vs. 2012-2015), we report a substantial decrease in genetic diversity. Phylogenetic analyses including neighboring populations identified two porpoises in southern Iberia carrying a divergent haplotype closely related to those from the Mauritanian population, yet forming a distinct lineage. This suggests that Iberian porpoises may not be as isolated as previously thought, indicating possible dispersion from Mauritania or an unknown population in between, but none from the northern ecotype. Demo-genetic scenario testing by approximate Bayesian computation showed that the rapid decline in the Iberian mitochondrial diversity was not simply due to the genetic drift of a small population, but models support instead a substantial decline in effective population size, possibly resulting from environmental stochasticity, prey depletion, or acute fishery bycatches. These results illustrate the value of genetics time series to inform demographic trends and emphasize the urgent need for conservation measures to ensure the viability of this small harbor porpoise population in Iberian waters.
摘要：
预计气候变化的影响在物种分布的边缘尤其明显，它们满足次优的栖息地条件。在毛里塔尼亚和伊比利亚，两个遗传分化的港口海豚种群（Phocoenaphocoena）形成了适应当地上升流条件的生态型，与东北大西洋大陆架和黑海北部的其他生态型不同。通过分析两个时间队列（1990-2002年与2012-2015),我们报告了遗传多样性的大幅下降。包括邻近种群在内的系统发育分析确定了伊比利亚南部的两只海豚，它们带有与毛里塔尼亚种群密切相关的不同单倍型，但形成了一个独特的血统。这表明伊比利亚海豚可能不像以前想象的那样孤立，表明来自毛里塔尼亚或两者之间未知人口的可能分散，但没有北方生态型。通过近似贝叶斯计算进行的演示遗传情景测试表明，伊比利亚线粒体多样性的迅速下降不仅仅是由于小种群的遗传漂移，但是模型支持有效人口规模的大幅下降，可能是由于环境的随机性，猎物耗尽，或急性渔业捕捞。这些结果说明了遗传学时间序列在告知人口趋势方面的价值，并强调迫切需要采取保护措施，以确保这种小港口海豚种群在伊比利亚水域的生存能力。
