West Virginia University, Department of Biology, P.O. Box 6057, Morgantown, West Virginia 26506 USA.
Am J Bot. 2007 Oct;94(10):1677-87. doi: 10.3732/ajb.94.10.1677.
For rare plants, self-pollination and inbreeding can increase in small populations, while unusual levels of outcrossing can occur through restoration efforts. To study both inbreeding and outcrossing, we performed experimental pollinations using Panax quinquefolius (American ginseng), a wild-harvested plant with a mixed mating system. For inbreeding, plants were either cross-pollinated within the population or self-pollinated, which resulted in a higher proportion of seeds from self-pollinated flowers. For outcrossing, wild plants were either cross-pollinated within the population or with cultivated plants from West Virginia or Wisconsin. Offspring of all crosses were followed for 4 yr. Two-yr-old seedlings from self-pollination had 45% smaller leaf areas and 33% smaller heights relative to those from cross-pollination. Leaf area is a positive predictor of longer-term survival in wild populations. Our results suggest inbreeding depression, which is unexpected in this self-fertile species. Seedlings from crosses with cultivated plants had 127% greater leaf area and 165% greater root biomass relative to outcrosses within the population. The accelerated growth suggests genetic differences between wild and cultivated populations, but outbreeding depression may not appear until later generations. Assessment of the ultimate fitness consequences of introducing cultivated genotypes requires monitoring over longer time periods.
对于珍稀植物来说，自交和近亲繁殖在小种群中会增加，而通过恢复努力，也会出现异常高水平的异交。为了研究自交和异交，我们对美洲人参（Panax quinquefolius）进行了实验授粉，这是一种具有混合交配系统的野生植物。在自交方面，植物要么在种群内进行异交，要么进行自交，这导致自交花产生的种子比例更高。在异交方面，野生植物要么在种群内进行异交，要么与来自西弗吉尼亚州或威斯康星州的栽培植物进行异交。所有杂交后代都进行了 4 年的跟踪研究。与异交相比，自交产生的 2 年生幼苗的叶片面积小 45%，高度小 33%。叶片面积是野生种群长期生存的积极预测因子。我们的研究结果表明存在自交衰退，这在这种自交可育的物种中是出乎意料的。与种群内异交相比，与栽培植物杂交的幼苗的叶片面积增加了 127%，根系生物量增加了 165%。这种加速生长表明野生和栽培种群之间存在遗传差异，但直到后代，异交衰退才会显现。要评估引入栽培基因型的最终适应度后果，需要在更长的时间内进行监测。
