Data from: QTL linkage mapping of zebra finch beak color shows an oligogenic control of a sexually selected trait

Mate choice based on sexual ornaments can impose strong selection, which raises the question of how genetic variation in ornaments is maintained. One mechanism that has been proposed is genic capture. If ornament expression is influenced by general condition and condition is under polygenic control, selection will be inefficient in removing genetic variation. Here we analyze whether the genetic architecture of beak color in a population of zebra finches supports this hypothesis. Zebra finch beak color is commonly assumed to be under strong selection by mate choice, although some of the evidence is ambiguous. We show that beak redness has a heritability of 34% in our population and that it is strongly genetically correlated between the sexes, suggesting that it is largely controlled by the same genes in males and females. We mapped variation in beak redness based on 1,404 SNP markers genotyped in a large pedigree. We find evidence for linkage on four chromosomes (Tgu1, Tgu5, Tgu13, Tgu21), which together explain a large part of the additive genetic variance. Our finding of genomic regions with major additive effects is not consistent with directional selection and genic capture, but rather suggests a role of antagonistic pleiotropy in maintaining genetic variation.

基于性装饰特征的配偶选择可施加强烈的选择压力，这一现象引出了关键科学问题：装饰性状的遗传变异如何得以维持。学界已提出的一种维持机制为基因捕获（genic capture）假说。若装饰性状的表达受个体整体生理状况调控，且该状况由多基因共同控制，则选择压力难以有效清除群体中的遗传变异。本研究以斑胸草雀（zebra finch）种群为对象，分析其喙色的遗传结构是否支持该假说。尽管部分研究证据尚存争议，但学界普遍认为斑胸草雀的喙色会受到配偶选择带来的强烈选择压力。本研究结果显示，本研究群体中喙部红色度的遗传力为34%，且雌雄个体间存在极强的遗传相关，表明该性状在雌雄个体中基本由同一套基因调控。本研究基于大型家系中完成基因分型的1404个单核苷酸多态性（SNP）标记，对喙部红色度的遗传变异进行了定位分析。最终在4条染色体（Tgu1、Tgu5、Tgu13、Tgu21）上检测到连锁信号，这些区域共同解释了大部分的加性遗传方差。本研究发现存在具有显著加性效应的基因组区域，这一结果与定向选择及基因捕获假说均不相符，反而提示拮抗多效性在维持该性状的遗传变异中发挥了重要作用。