Maret Timothy J, Collins James P
Department of Zoology, Arizona State University, Tempe, Arizona, 85287-1501.
Evolution. 1997 Jun;51(3):898-905. doi: 10.1111/j.1558-5646.1997.tb03671.x.
The role of ecological factors in promoting morphological diversity within and among species is an area of debate among evolutionary biologists. Using morphological differences between sympatric species as evidence that competition promotes divergence (e.g., character displacement), has, in particular, drawn harsh criticism because morphological differences may have evolved during allopatry. In contrast to species, alternative phenotypes within a species have a common phylogenetic history, so differences between phenotypes are likely to result from ecological conditions experienced in sympatry. Using cannibal and typical larval phenotypes of the Arizona tiger salamander, Ambystoma tigrinum nebulosum, we tested two predictions of the hypothesis that resource competition promotes morphological divergence: (1) larval phenotypes should reduce competition by using different resources; and (2) the advantage to developing the alternative, cannibal phenotype should be highest when competition among typical larvae is most intense. We used field surveys and a field experiment to test these predictions. The two larval phenotypes used different resources, especially when competition was intense. The advantage to individual larvae of becoming cannibals was highest when competition for resources among typical larvae was high. These results support the hypothesis that resource competition can promote morphological divergence.
生态因素在促进物种内部和物种之间形态多样性方面所起的作用，是进化生物学家们争论的一个领域。利用同域物种之间的形态差异作为竞争促进趋异（例如，性状替换）的证据，尤其受到了严厉批评，因为形态差异可能是在异域状态下进化而来的。与物种不同，一个物种内的替代表型具有共同的系统发育史，所以表型之间的差异很可能是同域状态下所经历的生态条件导致的。我们以亚利桑那虎螈（Ambystoma tigrinum nebulosum）的食同类幼虫和典型幼虫表型为研究对象，对资源竞争促进形态趋异这一假说的两个预测进行了检验：（1）幼虫表型应通过利用不同资源来减少竞争；（2）当典型幼虫之间的竞争最为激烈时，发育出替代的食同类表型的优势应该最大。我们通过实地调查和一项野外实验来检验这些预测。这两种幼虫表型利用不同的资源，尤其是在竞争激烈时。当典型幼虫之间对资源的竞争激烈时，个体幼虫成为食同类的优势最大。这些结果支持了资源竞争能够促进形态趋异这一假说。
