Department of Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
J Anim Ecol. 2023 Aug;92(8):1474-1477. doi: 10.1111/1365-2656.13964.
Animals usually change their trophic niche during their ontogeny, which has fundamental consequences for their population dynamics and interactions with other species. Theory predicts that ontogenetic niche differences between species can influence their ability to coexist. However, we lack empirical evidence for this coexistence mechanism and the role of evolution in shaping species' ontogenetic niches. Here, Anaya-Rojas et al. (2023) show that contemporary evolution of ontogenetic niches likely contributes to the coexistence of two competing fish species (killifish and guppies) in streams on the Caribbean Island of Trinidad. As predicted by coexistence theory, they found that the weaker competitor (killifish) exhibited a relatively large ontogenetic niche shift, feeding at higher trophic levels as it grew, in streams where competition with the stronger competitor (guppies) was intense. Intuition suggests that the weaker competitor should experience strong selection on its ontogenetic niche in a different competitive environment, but this was not the case. Instead, they found that the stronger competitor evolved a more compressed ontogenetic niche, where guppies fed at a low trophic level regardless of their body size, when competition was intense. Although the mechanism underlying this surprising result remains to be determined, this work points to the importance of taking a food web perspective-explicitly accounting for consumer-resource interactions-to understand the outcome of eco-evolutionary dynamics. Given that ontogenetic niche shifts are extremely common in animals, understanding the evolutionary ecology of these niche shifts should be a priority for future research on species coexistence.
动物在其个体发育过程中通常会改变其营养位，这对它们的种群动态和与其他物种的相互作用有根本的影响。理论预测，物种之间的个体发育营养位差异会影响它们共存的能力。然而，我们缺乏这种共存机制的经验证据，也缺乏进化在塑造物种个体发育营养位方面的作用的证据。在这里，Anaya-Rojas 等人（2023 年）表明，个体发育营养位的当代进化可能有助于两种竞争鱼类（食蚊鱼和孔雀鱼）在特立尼达加勒比岛屿的溪流中共存。正如共存理论所预测的那样，他们发现较弱的竞争者（食蚊鱼）表现出相对较大的个体发育营养位变化，随着生长而在更高的营养层次上觅食，在与较强的竞争者（孔雀鱼）竞争激烈的溪流中。直觉上认为，在不同的竞争环境中，较弱的竞争者的个体发育营养位应该受到强烈的选择，但事实并非如此。相反，他们发现，当竞争激烈时，较强的竞争者进化出了一个更紧凑的个体发育营养位，无论其体型大小，孔雀鱼都在低营养层次上觅食。尽管这一令人惊讶结果的背后机制仍有待确定，但这项工作表明，从食物网的角度——明确考虑消费者-资源相互作用——来理解生态进化动态的结果是很重要的。鉴于个体发育营养位的变化在动物中极为常见，了解这些营养位变化的进化生态学应该是未来关于物种共存的研究的重点。
