Data from: GxG epistasis in growth and condition and the maintenance of genetic polymorphism in Gambusia holbrooki

Theory on indirect genetic effects (IGEs) indicates that variation in the genetic composition of social groups can generate GxG epistasis that may promote the evolution of stable polymorphisms. Using a livebearing fish with a genetic polymorphism in coloration and associated behavioral differences, we tested whether genotypes of social partners interacted with focal individual genotypes to influence growth and condition over 16 weeks of development. We found that IGEs had a significant influence on patterns of feeding, regardless of focal fish genotype. There was no influence of social environment on juvenile length, but there was significant GxG epistasis for body condition. Each focal juvenile was in better condition when its own genotype was not present in adult social partners. These data are consistent with negative frequency-dependent selection in which each morph performs better when it is rare. Neither variation in feeding nor activity-related behaviors explained variation in body condition, suggesting that GxG epistasis for condition was caused by physiological differences between the two genotypes. These findings indicate that GxG epistasis in a given polymorphism can generate selection that contributes to the maintenance of that polymorphism and to maintenance of genetic variation for additional fitness-related traits.间接遗传效应（Indirect Genetic Effects, IGEs）理论表明，社会群体遗传组成的变异能够产生G×G上位性，这或许会推动稳定多态性的演化。本研究以体色存在遗传多态性且伴随行为差异的胎生鱼类为实验对象，开展了为期16周的发育实验，旨在探究社会伙伴的基因型与目标个体基因型是否会产生交互作用，进而影响个体生长与身体状况。研究结果显示，无论目标鱼类的基因型如何，间接遗传效应均会对摄食模式产生显著影响。社会环境对幼鱼体长并无显著影响，但身体状况指标却存在显著的G×G上位性效应。当成年社会伙伴的基因型中不存在目标幼鱼自身的基因型时，该目标幼鱼的身体状况更佳。上述数据与负频率依赖选择（negative frequency-dependent selection）理论相符：即当某一形态较为稀有时，其适配性表现更佳。摄食行为与活动相关行为的变异均无法解释身体状况的差异，这表明身体状况相关的G×G上位性效应是由两种基因型间的生理差异所导致的。本研究结果表明，特定多态性下的G×G上位性效应能够产生选择压力，进而助力该多态性的维持，同时也能维持与额外适合度相关性状的遗传变异。