Biology Program, George Mason University Fairfax, Virginia, 22030.
Smithsonian Migratory Bird Center, Smithsonian Conservation Biology Institute National Zoological Park, Washington, District of Columbia, 20008.
Ecol Evol. 2014 Mar;4(6):699-705. doi: 10.1002/ece3.911. Epub 2014 Feb 13.
Avian bills are iconic structures for the study of ecology and evolution, with hypotheses about the morphological structure of bills dating back to Darwin. Several ecological and physiological hypotheses have been developed to explain the evolution of the morphology of bill shape. Here, we test some of these hypotheses such as the role of habitat, ambient temperature, body size, intraspecific competition, and ecological release on the evolution of bill morphology. Bill morphology and tarsus length were measured from museum specimens of yellow warblers, and grouped by habitat type, sex, and subspecies. We calculated the mean maximum daily temperature for the month of July, the hottest month for breeding specimens at each collecting location. Analysis of covariance models predicted total bill surface area as a function of sex, habitat type, body size, and temperature, and model selection techniques were used to select the best model. Habitat, mangrove forests compared with inland habitats, and climate had the largest effects on bill size. Coastal wetland habitats and island populations of yellow warblers had similar bill morphology, both of which are larger than mainland inland populations. Temperate but not tropical subspecies exhibited sexual dimorphism in bill morphology. Overall, this study provides evidence that multiple environmental factors, such as temperature and habitat, contribute to the evolution of bill morphology.
鸟类的喙是研究生态学和进化的标志性结构，关于喙形态结构的假说可以追溯到达尔文时代。已经提出了几个生态和生理假说，以解释喙形状的形态进化。在这里，我们测试了一些假设，例如栖息地、环境温度、体型、种内竞争和生态释放对喙形态进化的作用。从黄莺的博物馆标本中测量了喙形态和跗跖长度，并按栖息地类型、性别和亚种进行分组。我们计算了每个采集地点繁殖标本的 7 月最热月份的平均最高日温度。协方差分析模型预测了总喙表面积作为性别、栖息地类型、体型和温度的函数，并使用模型选择技术选择了最佳模型。栖息地、与内陆栖息地相比的红树林，以及气候对喙大小的影响最大。沿海湿地栖息地和黄莺的岛屿种群具有相似的喙形态，两者都大于大陆内陆种群。温带而不是热带亚种在喙形态上表现出性别二态性。总的来说，这项研究提供了证据表明，多种环境因素，如温度和栖息地，有助于喙形态的进化。
