Omland K E, Lanyon S M
James Ford Bell Museum of Natural History and Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul 55108, USA.
Evolution. 2000 Dec;54(6):2119-33. doi: 10.1111/j.0014-3820.2000.tb01254.x.
Several empirical studies suggest that sexually selected characters, including bird plumage, may evolve rapidly and show high levels of convergence and other forms of homoplasy. However, the processes that might generate such convergence have not been explored theoretically. Furthermore, no studies have rigorously addressed this issue using a robust phylogeny and a large number of signal characters. We scored the appearance of 44 adult male plumage characters that varied across New World orioles (Icterus). We mapped the plumage characters onto a molecular phylogeny based on two mitochondrial genes. Reconstructing the evolution of these characters revealed evidence of convergence or reversal in 42 of the 44 plumage characters. No plumage character states are restricted to any groups of species higher than superspecies in the oriole phylogeny. The high frequency of convergence and reversal is reflected in the low overall retention index (RI = 0.66) and the low overall consistency index (CI = 0.28). We found similar results when we mapped plumage changes onto a total evidence tree. Our findings reveal that plumage patterns and colors are highly labile between species of orioles, but highly conserved within the oriole genus. Furthermore, there are at least two overall plumage types that have convergently evolved repeatedly in the three oriole clades. This overall convergence leads to significant conflict between the molecular and plumage data. It is not clear what evolutionary processes lead to this homoplasy in individual characters or convergence in overall pattern. However, evolutionary constraints such as developmental limitations and genetic correlations between characters are likely to play a role. Our results are consistent with the belief that avian plumage and other sexually selected characters may evolve rapidly and may exhibit high homoplasy. The overall convergence in oriole plumage patterns is an interesting evolutionary phenomenon, but it cautions against heavy reliance on plumage characters for constructing phylogenies.
多项实证研究表明，包括鸟类羽毛在内的性选择特征可能会迅速进化，并表现出高度的趋同以及其他形式的同塑性。然而，可能导致这种趋同的过程尚未从理论上进行探索。此外，尚无研究使用可靠的系统发育树和大量信号特征来严格解决这一问题。我们对44种成年雄性羽毛特征的外观进行了评分，这些特征在新大陆拟黄鹂（Icterus）中各不相同。我们将羽毛特征映射到基于两个线粒体基因的分子系统发育树上。对这些特征的进化进行重建后发现，44种羽毛特征中有42种存在趋同或逆转的证据。在拟黄鹂系统发育中，没有任何羽毛特征状态仅限于高于超种的任何物种组。趋同和逆转的高频率反映在较低的总体保留指数（RI = 0.66）和较低的总体一致性指数（CI = 0.28）上。当我们将羽毛变化映射到一个全证据树上时，也得到了类似的结果。我们的研究结果表明，拟黄鹂物种之间的羽毛图案和颜色非常不稳定，但在拟黄鹂属内却高度保守。此外，至少有两种总体羽毛类型在三个拟黄鹂分支中反复趋同进化。这种总体趋同导致分子数据和羽毛数据之间存在重大冲突。目前尚不清楚是哪些进化过程导致了个体特征中的这种同塑性或总体模式中的趋同。然而，诸如发育限制和特征之间的遗传相关性等进化限制可能起到了作用。我们的结果与鸟类羽毛和其他性选择特征可能迅速进化并可能表现出高度同塑性的观点一致。拟黄鹂羽毛图案的总体趋同是一个有趣的进化现象，但它提醒我们在构建系统发育树时不要过度依赖羽毛特征。
