Bolnick D I
Center for Population Biology, University of California, Davis 95616, USA.
Nature. 2001 Mar 22;410(6827):463-6. doi: 10.1038/35068555.
Ecologists have proposed that when interspecific competition is reduced, competition within a species becomes a potent evolutionary force leading to rapid diversification. This view reflects the observation that populations invading species-poor communities frequently evolve broader niches. Niche expansion can be associated with an increase in phenotypic variance (known as character release), with the evolution of polymorphisms, or with divergence into many species using distinct resources (adaptive radiation). The relationship between intraspecific competition and diversification is known from theory, and has been used as the foundation for some models of speciation. However, there has been little empirical proof that niches evolve in response to intraspecific competition. To test this hypothesis, I introduced cadmium-intolerant Drosophila melanogaster populations to environments containing both cadmium-free and cadmium-laced resources. Here I show that populations experiencing high competition adapted to cadmium more rapidly than low competition populations. This provides experimental confirmation that competition in a population can drive niche expansion onto new resources for which competition is less severe.
生态学家提出，当种间竞争减弱时，物种内部的竞争就会成为一股强大的进化力量，导致快速分化。这一观点反映了这样一个观察结果：侵入物种匮乏群落的种群常常会进化出更广泛的生态位。生态位扩展可能与表型变异的增加（称为性状释放）、多态性的进化，或与利用不同资源分化成许多物种（适应性辐射）有关。种内竞争与分化之间的关系从理论上是已知的，并已被用作一些物种形成模型的基础。然而，几乎没有实证证据表明生态位会因种内竞争而进化。为了验证这一假设，我将不耐镉的黑腹果蝇种群引入到既有无镉资源又有含镉资源的环境中。在此我表明，经历高竞争的种群比低竞争种群更快地适应了镉。这提供了实验证实，种群中的竞争可以推动生态位扩展到竞争不太激烈的新资源上。
