Data from: Heterozygosity predicts clutch and egg size but not plasticity in a house sparrow population with no evidence of inbreeding

We investigated the link between heterozygosity and the reaction norm attributes of reproductive performance in female house sparrows (Passer domesticus). We collected data on clutch size, egg size, hatching success, and nestling survival in 2 816 nesting attempts made by 791 marked individuals over a 16 year period. Pedigree analysis revealed no evidence of inbreeding. Neither parent-offspring regression nor an animal model revealed significant heritability in clutch or egg size. We selected 42 females that laid at least seven clutches at our study site and used a survey of 21 autosomal microsatellite loci to estimate heterozygosity for each female. We controlled for phenotypic plasticity and found that both clutch and egg size showed significant positive correlations with heterozygosity. We found no evidence that heterozygosity influenced the slope of individual reaction norms. Further analysis suggested that clutch size was affected by heterozygosity across the genome, but egg size had more complex relationships, with evidence favoring the influence of multiple loci. Given the apparent lack of inbreeding and large population size, our results suggest associative overdominance as the likely mechanism for the impact of heterozygosity, but also created a puzzle about the process producing associations between neutral markers and the genes affecting clutch size or egg size. One possible explanation is a long term residual effect of the historical bottleneck that occurred when house sparrows were introduced into North America. The existence of HFCs in a population with considerable phenotypic plasticity and little inbreeding implies that the effects of heterozygosity may be more significant than previously thought.本研究旨在探究雌性家麻雀（Passer domesticus）的杂合度与繁殖表现反应规范属性之间的关联。研究团队在16年的周期内，针对791只已标记个体的2816次筑巢尝试，收集了窝卵数、卵大小、孵化成功率及雏鸟存活率相关数据。系谱分析未发现近交迹象。无论是亲子回归分析还是动物模型分析，均未发现窝卵数或卵大小存在显著遗传力。我们选取了42只在研究区域内至少产7窝卵的雌性个体，通过对21个常染色体微卫星位点的检测分析，估算每只雌性的杂合度水平。在控制表型可塑性的影响后发现，窝卵数与卵大小均与杂合度呈现显著正相关。未发现杂合度对个体反应规范的斜率存在影响。进一步分析显示，窝卵数受全基因组杂合度的影响，而卵大小的关联更为复杂，现有证据支持其受多位点共同调控。鉴于研究群体几乎不存在近交且种群规模较大，本研究结果表明，关联超显性可能是杂合度产生影响的潜在机制，但同时也引出了一个谜题：即中性标记与调控窝卵数或卵大小的基因之间的关联究竟是通过何种过程形成的。其中一种可能的解释是，家麻雀被引入北美时经历的历史种群瓶颈所遗留的长期效应。在表型可塑性较强且近交程度极低的种群中发现杂合度-适合度相关性（heterozygosity-fitness correlations, HFCs），意味着杂合度的影响可能比此前研究所认为的更为显著。