Langerhans R Brian, Knouft Jason H, Losos Jonathan B
Department of Biology, Washington University, St. Louis, Missouri 63130-4899, USA.
Evolution. 2006 Feb;60(2):362-9.
Examples of convergent evolution suggest that natural selection can often produce predictable evolutionary outcomes. However, unique histories among species can lead to divergent evolution regardless of their shared selective pressures-and some contend that such historical contingencies produce the dominant features of evolution. A classic example of convergent evolution is the set of Anolis lizard ecomorphs of the Greater Antilles. On each of four islands, anole species partition the structural habitat into at least four categories, exhibiting similar morphologies within each category. We assessed the relative importance of shared selection due to habitat similarity, unique island histories, and unique effects of similar habitats on different islands in the generation of morphological variation in anole ecomorphs. We found that shared features of diversification across habitats were of greatest importance, but island effects on morphology (reflecting either island effects per se or phylogenetic relationships) and unique aspects of habitat diversification on different islands were also important. There were three distinct cases of island-specific habitat diversification, and only one was confounded by phylogenetic relatedness. The other two unique aspects were not related to shared ancestry but might reflect as-yet-unmeasured environmental differences between islands in habitat characteristics. Quantifying the relative importance of shared and unique responses to similar selective regimes provides a more complete understanding of phenotypic diversification, even in this much-studied system.
趋同进化的例子表明，自然选择通常能够产生可预测的进化结果。然而，物种间独特的历史会导致趋异进化，无论它们面临着共同的选择压力——而且一些人认为，这种历史偶然性产生了进化的主要特征。大安的列斯群岛的安乐蜥生态形态就是趋同进化的一个经典例子。在四个岛屿中的每一个岛屿上，安乐蜥物种都将结构栖息地划分为至少四类，每一类中都呈现出相似的形态。我们评估了由于栖息地相似性导致的共同选择、独特的岛屿历史以及相似栖息地对不同岛屿的独特影响在安乐蜥生态形态的形态变异产生过程中的相对重要性。我们发现，跨栖息地多样化的共同特征最为重要，但岛屿对形态的影响（反映岛屿本身的影响或系统发育关系）以及不同岛屿上栖息地多样化的独特方面也很重要。存在三种不同的岛屿特异性栖息地多样化情况，只有一种与系统发育相关性混淆。另外两个独特方面与共同祖先无关，但可能反映了岛屿在栖息地特征方面尚未测量到的环境差异。即使在这个被深入研究的系统中，量化对相似选择机制的共同和独特反应的相对重要性，也能更全面地理解表型多样化。
