PDF(Pubmed)
Abstract：
Many endangered species live in fragmented and isolated populations with low genetic variability, signs of inbreeding, and small effective population sizes - all features elevating their extinction risk. The flat-headed loach (Oreonectes platycephalus), a small noemacheilid fish, is widely across southern China, but only in the headwaters of hillstreams; as a result, they are spatially isolated from conspecific populations. We surveyed single nucleotide polymorphisms in 16 Hong Kong populations of O. platycephalus to determine whether loach populations from different streams were genetically isolated from each other, showed low levels of genetic diversity, signs of inbreeding, and had small contemporary effective population sizes. Estimates of average observed heterozygosity (HO = 0.0473), average weighted nucleotide diversity (πw = 0.0546) and contemporary effective population sizes (Ne = 10.2 ~ 129.8) were very low, and several populations showed clear signs of inbreeding as judged from relatedness estimates. The degree of genetic differentiation among populations was very high (average FST = 0.668), even over short geographic distances (<1.5 km), with clear patterns of isolation by distance. These results suggest that Hong Kong populations of O. platycephalus have experienced strong genetic drift and loss of genetic variability because sea-level rise after the last glaciation reduced connectedness among paleodrainages, isolating populations in headwaters. All this, together with the fact that the levels of genetic diversity and contemporary effective population sizes within O. platycephalus populations are lower than most other freshwater fishes, suggests that they face high local extinction risk and have limited capacity for future adaptation.
摘要：
许多濒危物种生活在分散和孤立的种群中，遗传变异性低，近亲繁殖的迹象,和小的有效种群规模-所有特征都提高了它们的灭绝风险。平头泥ach（Oreonectesplatyhealus），一条小鱼，遍布中国南方，但只在山坡的源头；结果，它们在空间上与特定种群隔离。我们调查了香港16个白头鱼种群的单核苷酸多态性，以确定来自不同溪流的泥炭种群是否在基因上相互分离，表现出低水平的遗传多样性，近亲繁殖的迹象,当代有效人口规模较小。平均观测杂合度的估计（HO=0.0473），平均加权核苷酸多样性(πw=0.0546)和当代有效种群规模(Ne=10.2~129.8)非常低，根据亲缘关系估计，几个种群显示出明显的近亲繁殖迹象。群体间的遗传分化程度很高(平均FST=0.668),即使在很短的地理距离（<1.5公里），有清晰的距离隔离模式。这些结果表明，香港O.platycalus种群经历了强烈的遗传漂移和遗传变异性丧失，因为最后一次冰川期后海平面上升降低了古排水沟之间的连通性，隔离源头人口。所有这一切,此外，白头翁种群的遗传多样性水平和当代有效种群规模低于大多数其他淡水鱼，表明它们面临很高的局部灭绝风险，并且未来的适应能力有限。
