Baruah Gaurav, Barabás György, John Robert
Faculty of Biology, Theoretical Biology University of Bielefeld Bielefeld Germany.
Division of Biology Linköping University Linköping Sweden.
Ecol Evol. 2025 Apr 25;15(4):e71336. doi: 10.1002/ece3.71336. eCollection 2025 Apr.
Models on the effects of individual variation often focus on pairwise interactions, but communities could harbor both pairwise and higher order interactions (HOIs). Theoretical studies on HOIs, where a third species modulates pairwise species competition, tend to assign them at random, even though they could be mediated and structured by one-dimensional traits. Here, we consider two different classes of models of both pairwise and higher order trait-mediated interactions: competition alleviated by increasing trait distance, and hierarchical competition where species higher in the hierarchy exert more competition on those lower and vice versa. Combining these models with evolutionary dynamics based on quantitative genetics, we compare their impact on species diversity, community pattern, and robustness of coexistence. Regardless of individual variation, trait-mediated HOIs generally do not promote and often hinder species coexistence, but there are some notable exceptions to this. We present an analytical argument to make sense of these results and argue that while the effects of trait-based HOIs on diversity may appear confusing on the surface, we can understand what outcome to expect in any given scenario by looking at the shape of the effective interaction kernel that arises from the joint action of pairwise and HOI terms. In addition, we find that (i) communities structured by competitive trait hierarchies are highly vulnerable to external perturbations, regardless of HOIs, and (ii) trait-based HOIs with distance-dependent competition create the most robust communities, with minimal impact from individual variation, and (iii) both individual variation and HOIs consistently lead to a more even distribution of species traits than would occur by chance. These findings suggest that trait-mediated HOIs foster coexistence only under special conditions, raising the question of whether HOIs must involve multiple traits to positively affect coexistence in competitive communities.
关于个体变异影响的模型通常聚焦于成对相互作用，但群落可能同时存在成对和高阶相互作用（HOIs）。关于高阶相互作用（即第三种物种调节成对物种竞争）的理论研究往往随机分配它们，尽管它们可能由一维性状介导并结构化。在这里，我们考虑两类不同的成对和高阶性状介导相互作用模型：通过增加性状距离缓解竞争，以及等级竞争，即等级较高的物种对等级较低的物种施加更多竞争，反之亦然。将这些模型与基于数量遗传学的进化动力学相结合，我们比较它们对物种多样性、群落格局和共存稳健性的影响。无论个体变异如何，性状介导的高阶相互作用通常不会促进，反而常常阻碍物种共存，但也有一些明显的例外。我们提出一个分析论证来解释这些结果，并认为虽然基于性状的高阶相互作用对多样性的影响表面上可能令人困惑，但通过观察由成对和高阶相互作用项的联合作用产生的有效相互作用核的形状，我们可以理解在任何给定情况下预期的结果。此外，我们发现：（i）由竞争性性状等级结构构建的群落极易受到外部干扰，无论高阶相互作用如何；（ii）具有距离依赖性竞争的基于性状的高阶相互作用创造了最稳健的群落，个体变异的影响最小；（iii）个体变异和高阶相互作用都始终导致物种性状分布比随机情况更均匀。这些发现表明，性状介导的高阶相互作用仅在特殊条件下促进共存，这就引出了一个问题，即高阶相互作用是否必须涉及多个性状才能对竞争群落中的共存产生积极影响。
