Trame A-M, Coddington A J, Paige K N
Institute for Environmental Studies, Department of Ecology, Ethology, and Evolution, University of Illinois, 1101 West Peabody Avenue, 61801, Urbana, Il, USA.
Oecologia. 1995 Sep;104(1):93-100. doi: 10.1007/BF00365567.
In thisstudy we combine field experiments, designed to test the predictions of optimal outcrossing theory in Agave schottii, with molecular genetic studies, using RAPD (random amplified polymorphic DNA), polymerase chain reaction to assess the underlying genetic hypothesis of optimal outcrossing theory. Initially, 48 "females" of A. schottii were hand-pollinated with pollen collected from 1 m, 10 m, 100 m, and 2500 m distances. Each female received all four distance treatments. Additionally, a subset of the focal females and their pollen donors were used in an analysis of genetic similarity across the four distances. Results of hand-pollinations showed that crosses of 1 m had significantly lower seed set than 10 m and 100 m crosses. Crosses of 2500 m had intermediate seed set. Combined relative fitness was significantly lower for 1 m crosses compared to 10 m crosses, while 100 m and 2500 m crosses were intermediate. Thus, A. schottii experiences inbreeding depression and a trend toward outbreeding depression. Genetic analyses showed a similar pattern: individuals 1 m apart had on average higher genetic similarity (proportion of bands shared) than individuals separated by greater distances, with a trend toward lower genetic similarity for plants located 2500 m distant. The observed spatial genetic patterns are likely maintained by the combined effects of clonal reproduction, clone longevity, limited seed dispersal and the substantial number of inbred progeny produced, counteracting distant allele transfer which tends to reduce population genetic structure. The correspondence between our ecological and genetic results indicates that RAPD markers are useful tools for assessing ecological phenomena.
在本研究中，我们将旨在检验肖特龙舌兰最佳异交理论预测结果的田间实验与分子遗传学研究相结合，利用随机扩增多态性DNA（RAPD）聚合酶链反应来评估最佳异交理论的潜在遗传假设。最初，对48株肖特龙舌兰“雌性植株”进行人工授粉，花粉采集自距离1米、10米、100米和2500米处。每株雌性植株都接受了所有四种距离处理。此外，还选取了一部分作为重点研究对象的雌性植株及其花粉供体，用于分析这四个距离下的遗传相似性。人工授粉结果表明，1米距离的杂交种子结实率显著低于10米和100米距离的杂交。2500米距离的杂交种子结实率处于中间水平。与10米距离的杂交相比，1米距离杂交的综合相对适合度显著较低，而100米和2500米距离的杂交处于中间水平。因此，肖特龙舌兰存在近交衰退和远交衰退趋势。遗传分析显示出类似的模式：相隔1米的个体平均遗传相似性（共享条带比例）高于相隔更远距离的个体，对于距离2500米的植株，遗传相似性有降低趋势。观察到的空间遗传模式可能是由克隆繁殖、克隆寿命、种子传播受限以及产生的大量近交后代的综合作用维持的，这些因素抵消了倾向于减少种群遗传结构的远距离等位基因转移。我们的生态学和遗传学结果之间的对应关系表明，RAPD标记是评估生态现象的有用工具。
