School of Biological Sciences, Washington State University, Pullman, WA, USA.
Proc Biol Sci. 2024 Jun;291(2025):20240586. doi: 10.1098/rspb.2024.0586. Epub 2024 Jun 19.
Stebbins hypothesized that selfing lineages are evolutionary dead ends because they lack adaptive potential. While selfing populations often possess limited nucleotide variability compared with closely related outcrossers, reductions in the genetic variability of quantitative characters remain unclear, especially for key traits determining selfing rates. Yellow monkeyflower () populations generally outcross and maintain extensive quantitative genetic variation in floral traits. Here, we study the Joy Road population (Bodega Bay, CA, USA) of , where individuals exhibit stigma-anther distances (SAD) typical of primarily selfing monkeyflowers. We show that this population is closely related to nearby conspecifics on the Pacific Coast with a modest 33% reduction in genome-wide variation compared with a more highly outcrossing population. A five-generation artificial selection experiment challenged the hypothesis that the Joy Road population harbours comparatively low evolutionary potential in stigma-anther distance, a critical determinant of selfing rate in . Artificial selection generated a weak phenotypic response, with low realized heritabilities (0.020-0.028) falling 84% below those measured for floral characters in more highly outcrossing . These results demonstrate substantial declines in evolutionary potential with a transition toward selfing. Whether these findings explain infrequent reversals to outcrossing or general limits on adaptation in selfers requires further investigation.
斯特宾斯假设自交谱系是进化的死胡同,因为它们缺乏适应潜力。虽然自交种群与近亲的异交种群相比,通常具有有限的核苷酸变异性,但数量性状的遗传变异性减少仍不清楚,特别是对于决定自交率的关键特征。黄猴面花()种群通常异交,并保持花部性状的广泛数量遗传变异。在这里,我们研究了(加利福尼亚州博德加湾的乔伊路)种群,其中个体表现出柱头-花药距离(SAD),这是主要自交猴面花的典型特征。我们表明,该种群与太平洋沿岸的近缘种密切相关,与更高度异交的种群相比,全基因组变异减少了 33%。一个五代人工选择实验挑战了这样一种假设,即乔伊路种群在柱头-花药距离方面具有相对较低的进化潜力,这是自交率的一个关键决定因素。人工选择产生了微弱的表型反应,实现的遗传力(0.020-0.028)低,比在更高度异交的中测量的花部性状的遗传力低 84%。这些结果表明,随着向自交的转变,进化潜力显著下降。这些发现是否解释了自交向异交的罕见逆转,或者自交者适应的一般限制,需要进一步研究。