Abstract：
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 (Mimulus guttatus) populations generally outcross and maintain extensive quantitative genetic variation in floral traits. Here, we study the Joy Road population (Bodega Bay, CA, USA) of M. guttatus, 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 Mimulus. 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 M. guttatus. 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.
摘要：
Stebbins假设自交谱系是进化的死胡同，因为它们缺乏适应潜力。虽然与密切相关的异类相比，自交群体通常具有有限的核苷酸变异性，数量性状遗传变异的减少仍不清楚，特别是对于决定自交率的关键性状。黄猴花（Mimulusguttatus）种群通常异交，并在花性状上保持广泛的数量遗传变异。这里,我们研究欢乐路的人口(博德加湾，CA,美国)M.guttatus，其中个体表现出主要自交猴花的典型柱头-花药距离（SAD）。我们表明，该种群与太平洋海岸附近的物种密切相关，与更高的异型种群相比，全基因组变异减少了33％。五代人工选择实验挑战了JoyRoad种群在柱头-花药距离上具有相对较低的进化潜力的假设，Mimulus中自交率的关键决定因素。人工选择产生了微弱的表型反应，实现的遗传力较低（0.020-0.028），比高度异交的M.guttatus的花性状测得的遗传力低84％。这些结果表明，随着向自交的过渡，进化潜力大幅下降。这些发现是否可以解释不经常逆转到异型或自适应性的一般限制，还需要进一步调查。
