Data from: Strong inbreeding depression in two Scandinavian populations of the self-incompatible perennial herb Arabidopsis lyrata

Inbreeding depression is a key factor influencing mating system evolution in plants, but current understanding of its relationship with selfing rate is limited by a sampling bias with few estimates for self-incompatible species. We quantified inbreeding depression (δ) over two growing seasons in two populations of the self-incompatible perennial herb Arabidopsis lyrata ssp. petraea in Scandinavia. Inbreeding depression was strong and of similar magnitude in both populations. Inbreeding depression for overall fitness across two seasons (the product of number of seeds, offspring viability, and offspring biomass) was 81% and 78% in the two populations. Chlorophyll deficiency accounted for 81% of seedling mortality in the selfing treatment, and was not observed among offspring resulting from outcrossing. The strong reduction in both early viability and late quantitative traits suggests that inbreeding depression is due to deleterious alleles of both large and small effect, and that both populations experience strong selection against the loss of self-incompatibility. A review of available estimates suggested that inbreeding depression tends to be stronger in self-incompatible than in self-compatible highly outcrossing species, implying that undersampling of self-incompatible taxa may bias estimates of the relationship between mating system and inbreeding depression.

近交衰退（inbreeding depression）是影响植物交配系统演化的关键因素，但目前学界对其与自交率之间的关联认知因抽样偏差而受限——现有针对自交不亲和物种（self-incompatible species）的相关估计数量极少。本研究于斯堪的纳维亚地区，针对两个种群的自交不亲和多年生草本植物Arabidopsis lyrata ssp. petraea，在两个生长季内对近交衰退系数δ进行了量化；两个种群的近交衰退程度均较强且量级相近。跨两季的整体适合度（为种子数量、后代活力与后代生物量的乘积）对应的近交衰退率，在两个种群中分别为81%与78%。自交处理组的幼苗死亡率中，有81%由叶绿素缺陷（chlorophyll deficiency）所致，而异交产生的后代中未观察到该缺陷。早期活力与后期数量性状均出现显著降低，这表明近交衰退由效应大小各异的有害等位基因（deleterious alleles）所致，且两个种群均对丧失自交不亲和性存在强烈的选择压力。对现有可用估计值的综述显示，自交不亲和物种的近交衰退程度往往强于自交亲和（self-compatible）的高度异交物种，这意味着对自交不亲和类群（taxa）的抽样不足，可能会导致交配系统与近交衰退间关联的估计出现偏差。