Section of Integrative Biology, University of Texas, Austin, TX 78712, USA.
Proc Biol Sci. 2010 Oct 7;277(1696):2915-24. doi: 10.1098/rspb.2010.0232. Epub 2010 May 12.
Theory and empirical evidence show that intraspecific competition can drive selection favouring the use of novel resources (i.e. niche expansion). The evolutionary response to such selection depends on genetic variation for resource use. However, while genetic variation might facilitate niche expansion, genetically diverse groups may also experience weaker competition, reducing density-dependent selection on resource use. Therefore, genetic variation for fitness on different resources could directly facilitate, or indirectly retard, niche expansion. To test these alternatives, we factorially manipulated both the degree of genetic variation and population density in flour beetles (Tribolium castaneum) exposed to both novel and familiar food resources. Using stable carbon isotope analysis, we measured temporal change and individual variation in beetle diet across eight generations. Intraspecific competition and genetic variation acted on different components of niche evolution: competition facilitated niche expansion, while genetic variation increased individual variation in niche use. In addition, genetic variation and competition together facilitated niche expansion, but all these impacts were temporally variable. Thus, we show that the interaction between genetic variation and competition can also determine niche evolution at different time scales.
理论和实证证据表明，种内竞争可以推动选择，有利于利用新资源（即生态位扩展）。这种选择的进化反应取决于资源利用的遗传变异。然而，虽然遗传变异可能促进生态位扩展，但遗传多样性的群体也可能经历较弱的竞争，从而减少对资源利用的密度依赖选择。因此，对不同资源的适应性遗传变异可能直接促进或间接阻碍生态位扩展。为了检验这些替代方案，我们在接触新的和熟悉的食物资源的面粉甲虫（Tribolium castaneum）中，因子分析了遗传变异和种群密度的程度。使用稳定的碳同位素分析，我们测量了 8 代甲虫饮食的时间变化和个体变异。种内竞争和遗传变异作用于生态位进化的不同组成部分：竞争促进了生态位扩展，而遗传变异增加了生态位利用的个体变异。此外，遗传变异和竞争共同促进了生态位扩展，但所有这些影响都是时间变化的。因此，我们表明，遗传变异和竞争之间的相互作用也可以在不同的时间尺度上决定生态位进化。
