School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.
Evolution. 2011 Apr;65(4):1203-11. doi: 10.1111/j.1558-5646.2010.01195.x. Epub 2010 Dec 22.
The role of environment as a selective agent is well-established. Environment might also influence evolution by altering the expression of genetic variation associated with phenotypes under selection. Far less is known about this phenomenon, particularly its contribution to evolution in novel environments. We investigated how environment affected the evolvability of body size in the threespine stickleback (Gasterosteus aculeatus). Gasterosteus aculeatus is well suited to addressing this question due to the rapid evolution of smaller size in the numerous freshwater populations established following the colonization of new freshwater habitats by an oceanic ancestor. The repeated, rapid evolution of size following colonization contrasts with the general observation of low phenotypic variation in oceanic stickleback. We reared an oceanic population of stickleback under high and low salinity conditions, mimicking a key component of the ancestral environment, and freshwater colonization, respectively. There was low genetic variation for body size under high salinity, but this variance increased significantly when fish were reared under low salinity. We therefore conclude that oceanic populations harbor the standing genetic variation necessary for the evolution of body size, but that this variation only becomes available to selection upon colonization of a new habitat.
环境作为一种选择代理人的作用是众所周知的。环境也可能通过改变与选择下的表型相关的遗传变异的表达来影响进化。关于这种现象，人们知之甚少，尤其是它对新环境中进化的贡献。我们调查了环境如何影响三刺鱼（Gasterosteus aculeatus）的体型可进化性。由于海洋祖先殖民新淡水栖息地后，大量淡水种群的体型迅速进化，三刺鱼非常适合解决这个问题。大小的反复快速进化与海洋刺鱼中普遍观察到的低表型变异形成鲜明对比。我们在高盐度和低盐度条件下饲养海洋刺鱼种群，分别模拟了祖先环境和淡水殖民的一个关键组成部分。在高盐度下，体型的遗传变异很低，但当鱼在低盐度下饲养时，这种变异显著增加。因此，我们得出结论，海洋种群拥有体型进化所需的遗传变异，但这种变异只有在殖民新栖息地时才会被选择利用。
