Effects of intraspecific phenotypic variation on species coexistence

Intraspecific variation can promote or inhibit species coexistence, both by increasing species' competitive abilities, and by altering the relative strengths of intraspecific and interspecific competition. Effects of intraspecific variation on coexistence can occur via complementarity of different variants, and via a selection effect: initially-variable populations are more likely to contain highly competitive variants that might determine the competitive ability of the population as a whole. We tested the effects of intraspecific variation and composition on coexistence by assaying the mutual invasibility of populations of two competing bean weevil species (Callosobruchus maculatus and C. chinensis) when each was initiated with one, three, or five genetically- and phenotypically-distinct lineages. Our results reveal that intraspecific variation is a double-edged sword for species coexistence. Increasing intraspecific variation increased species' abilities to invade, and to resist invas...种内变异（intraspecific variation）可通过提升物种竞争能力，以及改变种内竞争（intraspecific competition）与种间竞争（interspecific competition）的相对强度，对物种共存（species coexistence）产生促进或抑制作用。种内变异对物种共存的影响可通过不同变异型间的互补效应（complementarity）实现，亦可通过选择效应（selection effect）达成：初始具有遗传变异的种群更易携带高竞争力的变异型，此类变异型可决定种群整体的竞争能力。本研究通过检测两种竞争豆象（Callosobruchus maculatus 与 C. chinensis）种群的互侵性（mutual invasibility），探究了种内变异及其组成对物种共存的影响；实验中各供试种群均以1、3或5个遗传与表型均存在差异的谱系作为起始种群。研究结果表明，种内变异对于物种共存而言是一把双刃剑：提升种内变异可增强物种的入侵能力与抗入侵能力……