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 between 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 an 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.亲缘关系相近的鸟类物种，其体色图案往往存在显著差异。本研究以亲缘关系相近的鸟类物种为样本，探讨繁殖范围重叠（breeding sympatry，繁殖同域性）对体色图案差异演化的影响。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个系统发育独立对比进行了分析。研究发现，亲缘相近物种间的体色图案分化在同域支系间显著高于异域支系，但仅存在于中等程度的同域性水平（繁殖范围重叠率50%~80%）时。该模式表明，若亲缘相近物种拥有相似的体色图案，在中等同域性水平下会付出相应代价——这类代价可能包括杂交、种间攻击、信号空间竞争，或是间接影响体色图案的生态相互作用。随着同域性水平进一步升高，体色图案分化程度反而下降，这一现象提示存在三种可能性：定向选择的松弛、基因流阻碍增强，或是在更高同域性水平下抵消性选择的作用增强。我们还发现，同域与异域姊妹物种间的体色图案差异在低纬度地区最为显著。本研究的全球尺度与宽泛的类群覆盖范围表明，同域繁殖的亲缘相近物种间的体色图案分化在鸟类中广泛存在。