Different mating systems can strongly affect the extent of genetic diversity and population structure among species. Given the increased effects of genetic drift on reduced population size, theory predicts that species undergoing self-fertilisation should have greater population structure than outcrossed species; however, demographic dynamics may affect this scenario. The mangrove killifish clade is composed of the two only known examples of self-fertilising species among vertebrates (Kryptolebias marmoratus and Kryptolebias hermaphroditus). A third species in this clade, Kryptolebias ocellatus, inhabits mangrove forests in southeast Brazil; however, its mating system and patterns of genetic structure have been rarely explored. Here, we examined the genetic structure and phylogeographic patterns of K. ocellatus along its distribution, using mitochondrial DNA and microsatellites to compare its patterns of genetic structure with the predominantly selfing and often-syntopic, K. hermaphroditus. Our results indicate that K. ocellatus reproduces mainly by outcrossing, with no current evidence of selfing, despite being an androdioecious species. Our results also reveal a stronger population subdivision in K. ocellatus compared to K. hermaphroditus, contrary to the theoretical predictions based on reproductive biology of the two species. Our findings indicate that, although morphologically similar, K. ocellatus and K. hermaphroditus had remarkably different evolutionary histories when colonising the same mangrove areas in southeastern Brazil, with other factors (e.g., time of colonisation, dispersal/establishment capacity) having more profound effects on the current population structuring of those species than differences in mating systems.

中文翻译：

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不只是一目了然：同位和形态相似的红树林鳉鱼物种在巴西海岸显示出不同的交配系统和遗传结构模式

不同的交配系统可以强烈影响物种之间的遗传多样性和种群结构的程度。鉴于遗传漂变对种群规模减少的影响增加，理论预测，进行自体受精的物种应该比异交物种具有更大的种群结构；然而，人口动态可能会影响这种情况。红树林鳉鱼进化枝由脊椎动物中已知的两种自体受精物种（Kryptolebias marmoratus 和 Kryptolebias hermaphroditus）组成。该分支中的第三个物种 Kryptolebias ocellatus 栖息在巴西东南部的红树林中。然而，很少有人探索它的交配系统和遗传结构模式。在这里，我们研究了 K. ocellatus 沿其分布的遗传结构和系统地理学模式，使用线粒体 DNA 和微卫星将其遗传结构模式与主要自交且常同位的 K. hermaphroditus 进行比较。我们的结果表明，K. ocellatus 主要通过异交繁殖，目前没有自交的证据，尽管它是一种雌雄同体的物种。我们的结果还揭示了与 K. hermaphroditus 相比， K. ocellatus 的种群细分更强，这与基于两个物种生殖生物学的理论预测相反。我们的研究结果表明，尽管在形态上相似，K. ocellatus 和 K. hermaphroditus 在殖民巴西东南部的同一红树林地区时具有显着不同的进化历史，以及其他因素（例如，殖民时间、