Data from: Size-dependent mortality and competition interactively shape community diversity

Body size is recognized as a major factor in evolutionary processes mediating sympatric diversification and community structuring. Life-history types with distinct body sizes can result from two fundamental mechanisms, size-dependent competition and size-dependent mortality. While previous theoretical studies investigated these two processes in separation, the model analyzed here allows both selective forces to affect body-size evolution interactively. Here we show for the first time that in the presence of size-dependent competition, size-dependent mortality can give rise to multiple, coexisting size morphs representing the final outcomes of evolution. Moreover, our results demonstrate that interactions between size-dependent competition and mortality can create characteristic abrupt changes in size structure and non-monotonic patterns of biological diversity along continuous and monotonic environmental gradients. We find that the two selective forces differentially affect the body-size ratios of coexisting morphs: size-dependent competition results in small and relatively constant ratios, whereas size-dependent mortality can open niches for morphs that greatly differ in body size. We show that these differential effects result in characteristic distributions of size ratios across communities, which we suggest can help detect the concurrent action and relative influence of size-dependent competition and mortality in nature.体型被认为是演化过程中的关键介导因素，影响同域分化（sympatric diversification）与群落构建（community structuring）。具有差异化体型的生活史类型可通过两种基本机制产生：体型依赖型竞争（size-dependent competition）与体型依赖型死亡（size-dependent mortality）。既往理论研究多单独探讨这两种过程，而本文所分析的模型则允许两种选择压力交互作用于体型演化。我们首次证明，在存在体型依赖型竞争的前提下，体型依赖型死亡可催生多种共存的体型形态（size morphs），并将其作为演化的最终结果。此外，研究结果表明，体型依赖型竞争与死亡之间的交互作用，可在连续且单调的环境梯度（environmental gradients）上，催生体型结构的特征性急剧变化以及生物多样性（biological diversity）的非单调模式。我们发现，两种选择压力对共存形态的体型比率存在差异化影响：体型依赖型竞争会产生较小且相对恒定的比率，而体型依赖型死亡则可为体型差异悬殊的形态开辟生态位（niches）。我们进一步证明，这些差异化效应会形成群落间体型比率的特征性分布，我们认为这一分布特征可用于检测自然界中体型依赖型竞争与死亡的协同作用及其相对影响强度。