Department of Biology, University of North Carolina, Chapel Hill, NC, USA.
Proc Biol Sci. 2009 Dec 7;276(1676):4189-96. doi: 10.1098/rspb.2009.1337. Epub 2009 Sep 2.
Ecological character displacement--trait evolution stemming from selection to lessen resource competition between species--is most often inferred from a pattern in which species differ in resource-use traits in sympatry but not in allopatry, and in which sympatric populations within each species differ from conspecific allopatric populations. Yet, without information on population history, the presence of a divergent phenotype in multiple sympatric populations does not necessarily imply that there has been repeated evolution of character displacement. Instead, such a pattern may arise if there has been character displacement in a single ancestral population, followed by gene flow carrying the divergent phenotype into multiple, derived, sympatric populations. Here, we evaluate the likelihood of such historical events versus ongoing ecological selection in generating divergence in trophic morphology between multiple populations of spadefoot toad (Spea multiplicata) tadpoles that are in sympatry with a heterospecific and those that are in allopatry. We present both phylogenetic and population genetic evidence indicating that the same divergent trait, which minimizes resource competition with the heterospecific, has arisen independently in multiple sympatric populations. These data, therefore, provide strong indirect support for competition's role in divergent trait evolution.
生态特征替代——由于选择而导致的物种特征进化，以减轻物种之间的资源竞争——通常是从以下模式推断出来的：在同域中，物种在资源利用特征上存在差异，但在异域中不存在差异，并且在每个物种的同域种群中，与同种异地种群存在差异。然而，如果没有关于种群历史的信息，在多个同域种群中存在不同的表型并不一定意味着已经发生了多次特征替代的进化。相反，如果在一个单一的祖先种群中发生了特征替代，随后是携带不同表型的基因流进入多个衍生的同域种群，那么这种模式就可能出现。在这里，我们评估了这种历史事件与正在进行的生态选择在产生多个同域的锹形虫（Spea multiplicata）蝌蚪之间的营养形态差异的可能性，这些蝌蚪与异源种是同域的，而与同域的则是异源的。我们提出了系统发育和种群遗传证据，表明同一具有差异性的特征，即与异源种最小化资源竞争，已经在多个同域种群中独立出现。因此，这些数据为竞争在发散特征进化中的作用提供了强有力的间接支持。
