Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
Evolution. 2009 Nov;63(11):2831-7. doi: 10.1111/j.1558-5646.2009.00762.x. Epub 2009 Jun 22.
Adaptive radiation occurs when divergent natural selection in different environments leads to phenotypic differentiation. The pleiotropic effects of underlying genes can either promote or constrain this diversification. Identifying the pleiotropic effects of genes responsible for divergent traits, and testing how the environment influences these effects, can therefore help to provide an understanding of how ecology drives evolutionary change between populations. Positive selection on low-armor alleles at the Ectodysplasin (Eda) locus in threespine stickleback has led to the repeated evolution of reduced armor in populations following freshwater colonization by fully armored marine sticklebacks. Here, we demonstrate that Eda has environmentally determined pleiotropic effects on armor and growth. When raised in freshwater, reduced armor sticklebacks carrying "low" alleles at Eda had increased growth rate relative to fully armored sticklebacks carrying "complete" alleles. In saltwater treatments this growth advantage was present during juvenile growth but lost during adult growth, suggesting that in this environment stickleback are able to develop full armor plates without sacrificing overall growth rate. The environment specific pleiotropic effects of Eda demonstrate that ecological factors can mediate the influence of genetic architecture in driving phenotypic evolution. Furthermore, because size is important for mate choice in stickleback, the growth rate differences influenced by Eda may have effects on reproductive isolation between marine and freshwater populations.
当不同环境中的分歧性自然选择导致表型分化时，就会发生适应性辐射。基础基因的多效性效应可以促进或限制这种多样化。因此，确定导致分歧特征的基因的多效性效应，并测试环境如何影响这些效应，有助于了解生态如何在种群之间推动进化变化。在三种棘鱼的 Ectodysplasin（Eda）基因座上，低盔甲等位基因的正选择导致了完全有盔甲的海洋棘鱼淡水殖民后，种群中盔甲的重复进化。在这里，我们证明 Eda 对盔甲和生长具有环境决定的多效性效应。当在淡水中饲养时，携带“低”Eda 等位基因的减少盔甲棘鱼相对于携带“完整”等位基因的完全盔甲棘鱼具有更高的生长速度。在盐水处理中，这种生长优势存在于幼体生长期间，但在成体生长期间丧失，这表明在这种环境中，棘鱼能够发育出完整的盔甲板而不会牺牲整体生长速度。Eda 的环境特定多效性效应表明，生态因素可以调节遗传结构对表型进化的影响。此外，因为大小在棘鱼的配偶选择中很重要，所以 Eda 影响的生长速度差异可能对海洋和淡水种群之间的生殖隔离产生影响。
