PDF(Pubmed)
Abstract：
Landlocking of diadromous fish in freshwater systems can have significant genomic consequences. For instance, the loss of the migratory life stage can dramatically reduce gene flow across populations, leading to increased genetic structuring and stronger effects of local adaptation. These genomic consequences have been well-studied in some mainland systems, but the evolutionary impacts of landlocking in island ecosystems are largely unknown. In this study, we used a genotyping-by-sequencing (GBS) approach to examine the evolutionary history of landlocking in common smelt (Retropinna retropinna) on Chatham Island, a small isolated oceanic island 800 kilometres east of mainland New Zealand. We examined the relationship between Chatham Island and mainland smelt and used coalescent analyses to test the number and timing of landlocking events on Chatham Island. Our genomic analysis, based on 21,135 SNPs across 169 individuals, revealed that the Chatham Island smelt was genomically distinct from the mainland New Zealand fish, consistent with a single ancestral colonisation event of Chatham Island in the Pleistocene. Significant genetic structure was also evident within the Chatham Island smelt, with a diadromous Chatham Island smelt group, along with three geographically structured landlocked groups. Coalescent demographic analysis supported three independent landlocking events, with this loss of diadromy significantly pre-dating human colonisation. Our results illustrate how landlocking of diadromous fish can occur repeatedly across a narrow spatial scale, and highlight a unique system to study the genomic basis of repeated adaptation.
摘要：
在淡水系统中锁定泛鱼可能会产生重大的基因组后果。例如,迁徙生命阶段的丧失可以大大减少种群间的基因流动，导致增加的遗传结构和更强的局部适应效应。这些基因组后果已经在一些大陆系统中得到了很好的研究，但是内陆在岛屿生态系统中的进化影响在很大程度上是未知的。在这项研究中,我们使用基因分型测序（GBS）方法来检查查塔姆岛上普通冶炼（Retropinnaretrobinna）中内陆的进化史，新西兰大陆以东800公里的一个孤立的海洋小岛。我们研究了查塔姆岛与大陆冶炼物之间的关系，并使用合并分析来测试查塔姆岛上岸事件的数量和时间。我们的基因组分析，基于169个人的21,135个SNP，据透露，查塔姆岛的冶炼在基因上不同于新西兰大陆的鱼类，与更新世查塔姆岛的一次祖先殖民事件一致。在查塔姆岛冶炼中，重要的遗传结构也很明显，与查塔姆岛的一个完整的冶炼小组，以及三个地理结构的内陆群体。合并人口统计学分析支持三个独立的陆锁事件，由于这种diadromy的丧失大大早于人类殖民。我们的结果说明了在狭窄的空间范围内，横流鱼类的内陆如何反复发生，并突出了一个独特的系统来研究重复适应的基因组基础。
