Frye Christopher T, Neel Maile C
Natural Heritage Program Maryland Department of Natural Resources Wildlife and Heritage Service Wye Mills MD USA.
Department of Plant Science and Landscape Architecture University of Maryland College Park MD USA.
Evol Appl. 2016 Dec 26;10(6):551-562. doi: 10.1111/eva.12437. eCollection 2017 Jul.
Many rare and endemic species experience increased rates of self-fertilization and mating among close relatives as a consequence of existing in small populations within isolated habitat patches. Variability in self-compatibility among individuals within populations may reflect adaptation to local demography and genetic architecture, inbreeding, or drift. We use experimental hand-pollinations under natural field conditions to assess the effects of gene flow in 21 populations of the central Appalachian endemic that varied in population size and degree of isolation. We quantified the effects of distance from pollen source on pollination success and fruit set. Rates of self-compatibility varied dramatically among maternal plants, ranging from 0% to 100%. This variation was unrelated to population size or degree of isolation. Nearly continuous variation in the success of selfing and near-cross-matings via hand pollination suggests that expresses pseudo-self-fertility, whereby plants carrying the same S-allele mate successfully by altering the self-incompatibility reaction. However, outcrossing among populations produced significantly higher fruit set than within populations, an indication of drift load. These results are consistent with strong selection acting to break down self-incompatibility in these small populations and/or early-acting inbreeding depression expressed upon selfing.
由于生活在孤立栖息地斑块内的小种群中，许多珍稀和特有物种的自花受精率和近亲交配率有所增加。种群内个体间自交亲和性的差异可能反映了对当地人口统计学和遗传结构的适应、近亲繁殖或遗传漂变。我们在自然田间条件下进行实验性人工授粉，以评估基因流对阿巴拉契亚中部21个特有种群的影响，这些种群在种群大小和隔离程度上存在差异。我们量化了距花粉源的距离对授粉成功率和坐果率的影响。母本植物的自交亲和率差异很大，从0%到100%不等。这种差异与种群大小或隔离程度无关。通过人工授粉进行的自交和近交交配成功率几乎呈连续变化，这表明[物种名称]表现出假自交能育性，即携带相同S等位基因的植物通过改变自交不亲和反应而成功交配。然而，种群间的异交产生的坐果率明显高于种群内，这表明存在遗传漂变负荷。这些结果与强烈的选择作用相一致，这种选择作用打破了这些小种群中的自交不亲和性和/或自交时表现出的早期近亲繁殖衰退。
