Data from: Color patterns of closely-related bird species are more divergent at intermediate levels of breeding range sympatry

Closely-related species of birds often differ markedly in their color patterns. Here we examine the influence of breeding range overlap (breeding sympatry) on the evolution of color pattern differences in a sample of closely-related bird species. We used a sister-lineage method to analyze 73 phylogenetically-independent comparisons among 246 species and 39 families of birds worldwide. We found that divergence of color patterns among closely-related species was greater between sympatric than allopatric lineages, but only at intermediate levels of sympatry (50-80% breeding range overlap). This pattern suggests that closely-related species incur costs at intermediate levels of sympatry if they exhibit similar color patterns — costs that could include hybridization, interspecific aggression, competition for signaling space, or ecological interactions that secondarily influence color patterns. The decline in color pattern divergence with further increase in sympatry suggests either the relaxation of divergent selection, increased impediment of gene flow, or increased role for counteracting selection, at higher levels of sympatry. We also found that the differences in color pattern between sympatric and allopatric sister species were greatest at lower latitudes. The global scale and broad taxonomic coverage in our study suggest that the divergence of color patterns between sympatrically-breeding, closely-related species is widespread in birds. 17 pages, 1 table, 2 figures; Online Appendices亲缘关系密切的鸟类类群往往在体色模式上存在显著差异。本研究探讨了繁殖范围重叠（breeding range overlap）即繁殖同域分布（breeding sympatry）对亲缘鸟类类群体色模式分化演化的影响。我们采用姊妹支系分析法，对全球范围内246个鸟类物种、39个科的73组系统发育独立对比（phylogenetically-independent comparisons）开展了分析。研究结果显示，亲缘鸟类类群间的体色模式分化程度在同域分布支系中显著高于异域分布（allopatric）支系，但该现象仅存在于繁殖范围重叠度处于中等水平（50%~80%）的类群中。该模式表明，当中等程度的同域分布时，若亲缘物种呈现相似的体色模式，将承担相应演化成本——此类成本可能包括杂交、种间攻击、信号空间竞争，或间接影响体色模式的生态互作。随着同域分布程度进一步升高，体色模式分化程度反而下降，这一现象提示，在更高的同域分布水平下，定向选择发生松弛、基因流阻碍加剧，或拮抗选择的作用增强。我们还发现，同域与异域分布的姊妹物种间的体色模式差异在低纬度地区最为显著。本研究具备全球尺度与宽泛的类群覆盖范围，表明同域繁殖的亲缘物种间的体色模式分化在鸟类类群中广泛存在。本研究共17页正文、1张表格与2幅插图，另附在线附录。