Snowberg Lisa K, Bolnick Daniel I
Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA.
Am Nat. 2008 Nov;172(5):733-9. doi: 10.1086/591692.
Speciation with gene flow may be driven by a combination of positive assortative mating and disruptive selection, particularly if selection and assortative mating act on the same trait, eliminating recombination between ecotype and mating type. Phenotypically unimodal populations of threespine stickleback (Gasterosteus aculeatus) are commonly subject to disruptive selection due to competition for alternate prey. Here we present evidence that stickleback also exhibit assortative mating by diet. Among-individual diet variation leads to variation in stable isotopes, which reflect prey use. We find a significant correlation between the isotopes of males and eggs within their nests. Because egg isotopes are derived from females, this correlation reflects assortative mating between males and females by diet. In concert with disruptive selection, this assortative mating should facilitate divergence. However, the stickleback population remains phenotypically unimodal, highlighting the fact that assortative mating and disruptive selection do not guarantee evolutionary divergence and speciation.
有基因流的物种形成可能由正向选型交配和歧化选择共同驱动，特别是当选择和选型交配作用于同一性状时，会消除生态型和交配型之间的重组。三刺鱼（Gasterosteus aculeatus）表型单峰的种群通常因对替代猎物的竞争而受到歧化选择。在此，我们提供证据表明，三刺鱼也会根据食物进行选型交配。个体间的食物差异导致稳定同位素的差异，而稳定同位素反映了猎物的利用情况。我们发现巢穴中雄性和卵的同位素之间存在显著相关性。由于卵的同位素来自雌性，这种相关性反映了雄性和雌性之间基于食物的选型交配。与歧化选择协同作用，这种选型交配应会促进分化。然而，三刺鱼种群在表型上仍保持单峰，这突出了一个事实，即选型交配和歧化选择并不能保证进化分化和物种形成。
