Tisthammer Kaho H, Forsman Zac H, Toonen Robert J, Richmond Robert H
Kewalo Marine Laboratory, University of Hawaii at Manoa, Honolulu, HI, United States of America.
Department of Biology, San Francisco State University, San Francisco, CA, United States of America.
PeerJ. 2020 Feb 18;8:e8550. doi: 10.7717/peerj.8550. eCollection 2020.
We examined genetic structure in the lobe coral among pairs of highly variable and high-stress nearshore sites and adjacent less variable and less impacted offshore sites on the islands of Oahu and Maui, Hawaii. Using an analysis of molecular variance framework, we tested whether populations were more structured by geographic distance or environmental extremes. The genetic patterns we observed followed isolation by environment, where nearshore and adjacent offshore populations showed significant genetic structure at both locations (AMOVA = 0.04∼0.19, < 0.001), but no significant isolation by distance between islands. Strikingly, corals from the two nearshore sites with higher levels of environmental stressors on different islands over 100 km apart with similar environmentally stressful conditions were genetically closer ( = 0.0, = 0.73) than those within a single location less than 2 km apart ( = 0.04∼0.08, < 0.01). In contrast, a third site with a less impacted nearshore site (i.e., less pronounced environmental gradient) showed no significant structure from the offshore comparison. Our results show much stronger support for environment than distance separating these populations. Our finding suggests that ecological boundaries from human impacts may play a role in forming genetic structure in the coastal environment, and that genetic divergence in the absence of geographical barriers to gene flow might be explained by selective pressure across contrasting habitats.
我们研究了夏威夷瓦胡岛和毛伊岛上海岸附近高度可变且压力较大的地点与相邻的变化较小且受影响较小的近海地点之间的叶状珊瑚的遗传结构。使用分子方差分析框架，我们测试了种群结构是否更多地由地理距离或极端环境因素决定。我们观察到的遗传模式遵循环境隔离，即近岸和相邻近海种群在两个地点均表现出显著的遗传结构（分子方差分析F值=0.04∼0.19，P<0.001），但岛屿之间不存在显著的距离隔离。引人注目的是，来自相距100多公里的不同岛屿上环境压力水平较高且环境压力条件相似的两个近岸地点的珊瑚，其遗传关系比相距不到2公里的单个地点内的珊瑚更为密切（F值=0.0，P=0.73），而后者的F值为0.04∼0.08，P<0.01。相比之下，第三个近岸地点受影响较小（即环境梯度不太明显），与近海比较时未显示出显著的结构差异。我们的结果表明，与距离相比，环境对这些种群的分隔作用更强。我们的发现表明，人类影响造成的生态边界可能在沿海环境中遗传结构的形成中发挥作用，并且在没有基因流动地理障碍的情况下，遗传分化可能是由不同生境间的选择压力导致的。
