Stone Judy L, Motten Alexander F
Department of Biology, Duke University, Durham, North Carolina 27708, USA.
Evolution. 2002 Nov;56(11):2187-95. doi: 10.1111/j.0014-3820.2002.tb00143.x.
Genetically based variation in outcrossing rate generates lineages within populations that differ in their history of inbreeding. According to some models, mating-system modifiers in such populations will demonstrate both linkage and identity disequilibrium with fitness loci, resulting in lineage-specific inbreeding depression. Other models assert that differences among families in levels of inbreeding depression are mainly attributable to random accumulation of genetic load, unrelated to variation at mating-system loci. We measured female reproductive success of selfed and outcrossed progeny from naturally occurring lineages of Datura stramonium, a predominantly self-fertilizing annual weed that has heritable variation in stigma-anther separation, a trait that influences selfing rates. Progeny from inbred lineages (as identified by high degree of anther-stigma overlap) showed equal levels of seed production, regardless of cross type. Progeny from mixed lineages (as identified by relatively high separation between anthers and stigma) showed moderate levels of inbreeding depression. We found a significant correlation between anther-stigma separation and relative fitness of selfed and outcrossed progeny, suggesting that family-level inbreeding depression may be related to differences among lineages in inbreeding history in this population. Negative inbreeding depression in putatively inbred lineages may be due in part to additive effects or to epistatic interactions among loci.
基于遗传的异交率变异在种群中产生了具有不同近亲繁殖历史的谱系。根据一些模型，此类种群中的交配系统修饰因子将与适合度位点表现出连锁不平衡和同一位点上的不平衡，从而导致谱系特异性的近亲繁殖衰退。其他模型则断言，近亲繁殖衰退水平在不同家族间的差异主要归因于遗传负荷的随机积累，与交配系统位点的变异无关。我们测量了曼陀罗自然发生谱系中自交和异交后代的雌性繁殖成功率，曼陀罗是一种主要自花授粉的一年生杂草，其柱头-花药间距存在可遗传变异，这一性状会影响自交率。自交系谱系（通过花药-柱头高度重叠识别）的后代，无论杂交类型如何，种子产量水平相同。混合谱系（通过花药与柱头相对较高的间距识别）的后代表现出中等程度的近亲繁殖衰退。我们发现花药-柱头间距与自交和异交后代的相对适合度之间存在显著相关性，这表明在该种群中，家族水平的近亲繁殖衰退可能与谱系间近亲繁殖历史的差异有关。推测的自交系谱系中的负向近亲繁殖衰退可能部分归因于加性效应或位点间的上位性相互作用。
