Kent Cody M, Sherry Thomas W
Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana, 70118, USA.
Ecology. 2020 Aug;101(8):e03077. doi: 10.1002/ecy.3077. Epub 2020 May 20.
Behavioral niche partitioning is an important and widely assumed mechanism for the coexistence of ecologically similar species. Here we assessed this mechanism by testing its core assumption, that evolved differences in foraging behavior correspond with differences in resources consumed. We combined data on foraging behavior, available prey, and observed diets of five coexisting species of New World wood warblers (Parulidae), a system that has been foundational to our understanding of behavioral niche partitioning. Consistent with past work, we found that the five species differed markedly in their foraging behavior, enough that some species pairs hardly overlapped at all in foraging microhabitat. In contrast, the birds overlapped highly in diet, while exhibiting small, interpretable differences in resource use. The high overlap resulted mostly from all five species consuming numerous ants, a prey source that moves between microhabitats. To test the prediction that the large differences in foraging behavior explain the small dietary differences, we generated expected diets based on available prey and foraging microhabitat use. Consistent with niche partitioning as a coexistence mechanism, we found that the small dietary differences were explained by a combination of foraging microhabitat and available prey, but this pattern was driven by only a small number of prey taxa. Thus, we found mixed support for behavioral niche partitioning. Our results indicate that foraging behavior among these bird species helps explain subtle variation in diet, potentially facilitating coexistence. However, our results also revealed a weak relationship between foraging behavior and resource partitioning. Consequently, studies that rely solely on foraging behavior may greatly overestimate the degree of niche differentiation leading to erroneous conclusions. Overall, this study calls into question how and why these differences in foraging behavior evolved, and what role if any they play in facilitating coexistence.
行为生态位划分是生态相似物种共存的一种重要且被广泛假定的机制。在此，我们通过检验其核心假设来评估这一机制，即觅食行为的进化差异与所消耗资源的差异相对应。我们整合了关于五种共存的新大陆林莺（森莺科）的觅食行为、可得猎物及观察到的食谱数据，该系统一直是我们理解行为生态位划分的基础。与以往研究一致，我们发现这五个物种在觅食行为上有显著差异，以至于一些物种对在觅食微生境上几乎没有重叠。相比之下，这些鸟类在食谱上有高度重叠，同时在资源利用上表现出细微且可解释的差异。高度重叠主要是因为所有五个物种都捕食大量蚂蚁，而蚂蚁这种猎物来源会在微生境之间移动。为了检验觅食行为的巨大差异解释了微小的食谱差异这一预测，我们根据可得猎物和觅食微生境利用情况生成了预期食谱。与生态位划分作为一种共存机制相符，我们发现微小的食谱差异是由觅食微生境和可得猎物共同解释的，但这种模式仅由少数猎物类群驱动。因此，我们对行为生态位划分的支持程度不一。我们的结果表明，这些鸟类物种间的觅食行为有助于解释食谱中的细微变化，可能促进了共存。然而，我们的结果也揭示了觅食行为与资源划分之间的微弱关系。因此，仅依赖觅食行为的研究可能会大大高估生态位分化程度，从而得出错误结论。总体而言，这项研究对这些觅食行为差异如何以及为何进化，以及它们在促进共存中是否发挥作用（若有作用则发挥何种作用）提出了质疑。
