Nagy Eric S
Section of Evolution and Ecology, Center for Population Biology, University of California, Davis, California, 95616.
Evolution. 1997 Oct;51(5):1469-1480. doi: 10.1111/j.1558-5646.1997.tb01470.x.
Gene exchange between locally adapted plant populations can have significant evolutionary consequences, including changes in genetic diversity, introduction of adaptive or maladaptive traits, disruptive of coadaptive gene complexes, and the creation of new ecotypes or even species. The potential for introgression between divergent populations will depend on the strength of selection against nonnative characters. Morphologically variable F hybrids of two Gilia capitata subspecies were used to evaluate the strength of phenotypic selection and the response to selection in the home habitats of each subspecies. At both sites, traits diagnostic of the subspecies were subject to significant phenotypic selection, probably mediated by direct selection on unmeasured correlated characters. Phenotypic selection favored native morphologies in all but a single case; leaf shape of one subspecies was favored in both habitats. The strength of selection varied between sites, with one site selecting more strongly against nonnative characters. Offspring of the F hybrids showed a significant evolutionary response to selection when grown in a common environment. Evolution was in the direction of similarity with the subspecies native to the site where selection was imposed. This result reveals that native character states are adaptive and suggests that selection will maintain native morphologies even after a substantial influx of genes from an ecologically and morphologically distinct, and locally adapted subspecies.
本地适应的植物种群之间的基因交换可能会产生重大的进化后果，包括遗传多样性的变化、适应性或非适应性性状的引入、共适应基因复合体的破坏，以及新生态型甚至新物种的产生。不同种群之间基因渗入的可能性将取决于对非本地性状的选择强度。利用两种头花吉莉草亚种形态可变的F1杂种来评估表型选择的强度以及每个亚种原生栖息地中对选择的响应。在两个地点，诊断亚种的性状都受到了显著的表型选择，这可能是由对未测量的相关性状的直接选择介导的。除了一个单一的案例外，表型选择都有利于本地形态；在两个栖息地中，一个亚种的叶形都受到青睐。选择强度在不同地点有所不同，其中一个地点对非本地性状的选择更为强烈。当在共同环境中生长时，F1杂种的后代对选择表现出显著的进化响应。进化朝着与施加选择的地点的本地亚种相似的方向发展。这一结果表明本地性状状态是适应性的，并表明即使在来自生态和形态上不同且本地适应的亚种的大量基因涌入之后，选择仍将维持本地形态。
