Data from: Multicontinental community phylogenetics of avian mixed-species flocks reveal the role of the stability of associations and of kleptoparasitism

If understood as a way to forage socially without incurring intra-specific competition for mates or other resources, mixed-species foraging flocks are predicted to be composed of functionally similar species. In the most intensively studied mixed-species foraging system, understory forest birds, relevant functional traits are however extremely difficult to measure and best replaced by phylogenetic relatedness. A multicontinental analysis of flock phylogenetic structure revealed departures from the expected phylogenetic clustering. Long-lasting associations (> one day) were phylogenetically overdispersed, indicating that these associations are affected by competitive exclusion or by mutualistic interactions. However, where kleptoparasites occurred, this effect disappeared completely, as expected if the dilution of kleptoparasitism risk compensated competition between related species. Mixed-species flocks should not be analyzed as a homogeneous phenomenon.

若将混合物种种群觅食群（mixed-species foraging flocks）视为一种可规避种内（配偶或其他资源）竞争的社会性觅食策略，则其组成物种理论上应具备相似的功能性状。在研究最为深入的混合物种种群觅食系统——林下鸟类觅食群中，相关功能性状极难量化，因此最适宜用系统发育亲缘关系（phylogenetic relatedness）替代。一项跨大陆的觅食群系统发育结构分析显示，其结果与预期的系统发育聚集模式存在偏差。持续时长超过一日的长期关联，其系统发育分布呈现过度分散特征，这表明此类关联受到竞争排除或互利共生相互作用的影响。然而，当盗寄生（kleptoparasitism）生物存在时，这一效应会完全消失——正如预期那般，若盗寄生风险的稀释效应能够抵消近缘物种间的竞争，则会出现此种结果。混合物种种群觅食群不应被视为单一均质的现象进行分析。