Data from: Genotype-dependent responses to levels of sibling competition over maternal resources in mice

Research on phenotypic plasticity has often focused on how a given genotype responds to changing physical environments. However, for many species the social environment plays an equally important role due to competition for resources. During early development, the level of competition for limited resources will often depend critically on the number of siblings. Therefore, competition among siblings should drive the evolution of genes that allow flexible responses to realized levels of competition and maternal resource availability. However, it is unknown whether genetically based differences between individuals exist in their response to the social environment that affects their future development. Using a quantitative trait locus approach in an experimental population of mice we demonstrate that effects of sibling number on body weight depend on individual genotype at seven loci, over and above the general negative litter size effect. Overall, these litter size-by-genotype interactions considerably modified the degree to which increasing litter size caused reduced weight. For example at one locus this effect leads to a 7% difference in body weight at week 7 between individuals experiencing the extremes of the normal range of litter sizes in our population (five to nine). The observed interaction between genotype and the competitive environment can produce differences in body weight that are similar in magnitude to the main effect of litter size on weight. Our results show that different genotypes respond to the social environment differentially and that interaction effects of genotype with litter size can be as important as genotype-independent effects of litter size.

表型可塑性（phenotypic plasticity）研究通常聚焦于特定基因型如何响应不断变化的物理环境。然而，对于诸多物种而言，社会环境因资源竞争的存在也发挥着同等重要的作用。在个体发育早期，有限资源的竞争激烈程度通常关键取决于同胞数量。因此，同胞间的竞争理应推动那些能够灵活响应实际竞争强度与母体资源供给状况的基因演化。然而，目前尚不清楚个体间是否存在基于遗传的差异，进而在响应影响其后续发育的社会环境时表现出不同表现。我们在小鼠实验种群中采用数量性状位点（quantitative trait locus, QTL）分析方法，证实除了一般的窝产仔数负面效应外，同胞数量对体重的影响还取决于7个位点上的个体基因型。总体而言，这些窝产仔数与基因型的交互作用显著改变了窝产仔数增加所导致的体重降低幅度。例如，在某一位点上，当个体分别处于本实验种群正常窝产仔数范围的极端值（5至9只）时，该效应会导致第7周时的体重出现7%的差异。本次研究观察到的基因型与竞争环境间的交互作用，可产生与窝产仔数对体重的主效应量级相近的体重差异。本研究结果表明，不同基因型对社会环境的响应存在差异，且基因型与窝产仔数的交互效应，其重要性可等同于窝产仔数的非基因型依赖效应。