Ecological opportunities, such as access to a novel habitat or the extirpation of a key competitor, can lead to adaptive divergence by exposing populations to diversifying selection. Typically, effects of ecological opportunity on adaptive divergence are inferred from macroevolutionary patterns rather than tested in populations undergoing contemporary divergence. This limits our insight on how ecological conditions contribute to adaptive divergence. Pumpkinseed sunfish (Centrarchidae: Lepomis gibbosus ) have recently and repeatedly colonized a ‘novel’ pelagic habitat in postglacial lakes, and subsequently undergone phenotypic diversification. We investigated whether ecological opportunity has contributed to diversification in a pumpkinseed population that has diversified between lake habitats. We used a between-year mark-recapture study to evaluate whether (1) the novel pelagic habitat represents an ecological opportunity by supporting a large, high-density population, and (2) connectivity between ecotype populations is restricted by limited adult dispersal. We found that phenotypic variation is spatially structured between habitats, similar to prior studies. Submerged shoals in the pelagic habitat do sustain a large adult population at a density seven times greater than the ancestral littoral habitat. Additionally, body condition and size of pelagic pumpkinseed is similar to littoral pumpkinseed. This suggests the pelagic habitat provides an ecological opportunity to pumpkinseed in the form of abundant, available resources. Furthermore, strong between-year habitat fidelity suggests aspects of the ecological opportunity have reduced adult dispersal and could limit gene flow. In combination with prior evidence indicating diversifying selection between habitats, these results provide an example of how ecological opportunity might contribute to contemporary adaptive divergence.

中文翻译：

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翻车鱼生态型同域种群之间的低连通性表明生态机会有助于多样化

生态机会，例如进入新的栖息地或消灭主要竞争者，可以通过将种群暴露于多样化选择来导致适应性差异。通常，生态机会对适应性分化的影响是从宏观进化模式中推断出来的，而不是在经历当代分化的人群中进行测试。这限制了我们对生态条件如何导致适应性差异的洞察。南瓜籽翻车鱼（Centrarchidae：Lepomis gibbosus）最近并反复在冰后湖泊中的“新”远洋栖息地定居，随后经历了表型多样化。我们调查了生态机会是否有助于在湖泊栖息地之间多样化的南瓜籽种群的多样化。我们使用年间标记重新捕获研究来评估 (1) 新的远洋栖息地是否通过支持大量、高密度的种群来代表生态机会，以及 (2) 生态型种群之间的连通性是否受到有限的成虫散布的限制。我们发现表型变异在栖息地之间具有空间结构，类似于先前的研究。远洋栖息地中的水下浅滩确实以比祖先沿海栖息地高七倍的密度维持着大量的成年人口。此外，远洋南瓜籽的体况和大小与沿海南瓜籽相似。这表明远洋栖息地以丰富的可用资源的形式为南瓜籽提供了生态机会。此外，强烈的年间栖息地保真度表明生态机会的某些方面减少了成虫的传播，并可能限制基因流动。结合先前表明栖息地之间选择多样化的证据，这些结果提供了一个例子，说明生态机会如何促进当代适应性分化。