Evaluating the fitness of hybrids can provide important insights into genetic differences between species or diverging populations. We focused on surface- and cave-ecotypes of the widespread Atlantic molly Poecilia mexicana and raised F1 hybrids of reciprocal crosses to sexual maturity in a common-garden experiment. Hybrids were reared in a fully factorial 2x2 design consisting of lighting (light vs. darkness) and resource availability (high vs. low food). We quantified survival, ability to realize their full reproductive potential (i.e., completed maturation for males and three consecutive births for females) and essential life-history traits. Compared to the performance of pure cave and surface fish from a previous experiment (Riesch et al. 2011, 2016), F1s had the highest death rate and the lowest proportion of fish that reached their full reproductive potential. We also uncovered an intriguing pattern of sex-specific phenotype expression, because male hybrids expressed cave molly life histories, while female hybrids expressed surface molly life histories. Our results provide evidence for strong selection against hybrids in the cave molly system, but also suggest a complex pattern of sex-specific (opposing) dominance, with certain surface molly genes being dominant in female hybrids and certain cave molly genes being dominant in male hybrids.

中文翻译：

---

洞穴和水面鱼类杂交种的性别特异性生活史特征表达（Poecilia mexicana，Poeciliidae）

评估杂交种的适应性可以为了解物种或不同种群之间的遗传差异提供重要的见解。我们专注于广泛分布的 Atlantic molly Poecilia mexicana 的地表和洞穴生态型，并在普通花园实验中将相互杂交的 F1 杂交种培育到性成熟期。杂交种在全因子 2x2 设计中饲养，包括照明（光照与黑暗）和资源可用性（高食物与低食物）。我们量化了存活率、实现其全部生殖潜能的能力（即雄性完全成熟和雌性连续生育三胎）和基本生活史特征。与之前实验中纯洞穴鱼和表层鱼的性能相比（Riesch 等人，2011 年、2016 年），F1s 的死亡率最高，而达到其完全繁殖潜力的鱼的比例最低。我们还发现了一种有趣的性别特异性表型表达模式，因为雄性杂交种表达了洞穴茉莉生活史，而雌性杂交种表达了地表茉莉生活史。我们的结果提供了在 cave molly 系统中针对杂种的强烈选择的证据，但也表明了一种复杂的性别特异性（相反）优势模式，某些表面 molly 基因在雌性杂交种中占优势，而某些 cave molly 基因在雄性杂交种中占优势.