Data from: Assortative mating but no evidence of genetic divergence in a species characterized by a trophic polymorphism

Disruptive selection is a process that can result in multiple subgroups within a population, which is referred to as diversification. Foraging-related diversification has been described in many taxa, but many questions remain about the contribution of such diversification to reproductive isolation and potentially sympatric speciation. Here, we use stable isotope analysis of diet and morphological analysis of body shape to examine phenotypic divergence between littoral and pelagic foraging ecomorphs in a population of pumpkinseed sunfish (Lepomis gibbosus). We then examine reproductive isolation between ecomorphs by comparing the isotopic compositions of nesting males to eggs from their nests (a proxy for maternal diet) and use nine microsatellite loci to examine genetic divergence between ecomorphs. Our data support the presence of distinct foraging ecomorphs in this population and indicate that there is significant positive assortative mating based on diet. We did not find evidence of genetic divergence between ecomorphs, however, indicating that isolation is either relatively recent or is not strong enough to result in genetic divergence at the microsatellite loci. Based on our findings, pumpkinseed sunfish represent a system in which to further explore the mechanisms by which natural and sexual selection contribute to diversification, prior to the occurrence of sympatric speciation.分裂选择（Disruptive selection）是一种可使种群内产生多个亚群的演化过程，该过程亦被称为物种分化。目前已有诸多类群（taxa）被报道存在与觅食相关的物种分化，但这类分化对生殖隔离（reproductive isolation）以及潜在同域物种形成（sympatric speciation）的贡献仍存在诸多待解问题。本研究以南瓜籽太阳鱼（Lepomis gibbosus）的一个自然种群为研究对象，通过饮食稳定同位素分析（stable isotope analysis）与体形形态学分析，探究沿岸带与远洋带觅食生态型间的表型分化特征。随后，我们通过对比筑巢雄鱼与巢内鱼卵的同位素组成（鱼卵同位素组成可作为母本饮食的替代指标），检测生态型间的生殖隔离情况；同时利用9个微卫星位点分析生态型间的遗传分化。研究数据证实该种群中存在特征显著的觅食生态型，且表明存在基于饮食的显著正选型交配现象。但我们未检测到生态型间存在遗传分化的证据，这提示生殖隔离要么形成时间相对较近，要么强度不足以在微卫星位点层面引发遗传分化。基于本研究结果，南瓜籽太阳鱼可作为一个理想研究体系，用于在同域物种形成发生之前，进一步探究自然选择与性选择推动物种分化的内在机制。