Data from: Has the inbreeding load for a condition-dependent sexual signalling trait been purged in insular lizard populations?

Sexually selected traits are often condition-dependent and are expected to be affected by genome-wide distributed deleterious mutations and inbreeding. However, sexual selection is a powerful selective force that can counteract inbreeding through purging of deleterious mutations. Inbreeding and purging of the inbreeding load for sexually selected traits has rarely been studied across natural populations with different degrees of inbreeding. Here we investigate inbreeding effects (measured as marker-based heterozygosity) on condition-dependent sexually selected signalling trait and other morphological traits across islet- and mainland populations (n = 15) of an endemic lizard species (Podarcis gaigeae). Our data suggest inbreeding depression on a condition-dependent sexually selected signalling character among mainland subpopulations with low or intermediate levels of inbreeding, but no sign of inbreeding depression among small and isolated islet populations despite their higher overall inbreeding levels. In contrast, there was no such pattern among ten other morphological traits which are primarily naturally selected and presumably not involved in sexual signalling. These results are in line with purging of recessive deleterious alleles, or purging in combination with stochastic fixation of alleles by genetic drift, for a sexual signalling character in the islet environment, which is characterized by low population sizes and strong sexual selection. Higher clutch sizes in islet populations also raise interesting questions regarding the possibility of antagonistic pleiotropy. Purging and other non-exclusive explanations of our results are discussed.性选择性状（sexually selected traits）通常具有条件依赖性，且易受全基因组分布的有害突变与近交的影响。然而，性选择作为一种强有力的选择压力，可通过清除有害突变抵消近交的负面效应。针对性选择性状的近交与近交负荷清除研究，在不同近交程度的自然种群中仍较为少见。本研究以一种特有蜥蜴（Podarcis gaigeae）的岛屿与大陆种群（共15个）为对象，探究以基于分子标记的杂合度为衡量指标的近交效应对条件依赖性性选择信号性状及其他形态性状的影响。研究数据显示，在近交程度较低或中等的大陆亚种群中，条件依赖性性选择信号性状存在近交衰退（inbreeding depression）现象；而在种群规模更小、隔离程度更高的岛屿种群中，尽管整体近交水平更高，却未观察到近交衰退的迹象。与之形成鲜明对比的是，其余10种主要受自然选择、且不参与性信号传递的形态性状并未呈现此类模式。上述结果与岛屿环境中性信号性状的清除效应相符：岛屿环境以小种群规模与强烈的性选择为特征，其清除隐性有害等位基因，或是结合遗传漂变（genetic drift）导致的等位基因随机固定效应，均可解释该结果。岛屿种群更大的窝卵数也为拮抗多效性（antagonistic pleiotropy）的可能性提出了有趣的研究问题。本研究还讨论了清除效应及其他非排他性的结果解释路径。