Cheptou Pierre-Olivier, Schoen Daniel J
Department of Biology, McGill University, 1205 Dr. Penfield Avenue, Montreal, Quebec H3A 1B1, Canada.
Am Nat. 2003 Dec;162(6):744-53. doi: 10.1086/378902. Epub 2003 Dec 19.
If the competitive ability of plants produced by self-pollination differs from that of plants derived by outcrossing, then the magnitude of inbreeding depression may be influenced by the composition of the competitive environment (i.e., the frequency of plants that have arisen from selfing and outcrossing in the neighborhood of "target" plants in which inbreeding depression is expressed). Here, we report the results of experiments designed to examine whether inbreeding depression is influenced by the frequency of inbred plants in the competitive neighborhood. Two species of the annual plant genus Amsinckia were studied, one a near-complete selfer (Amsinckia gloriosa) and the other a partial outcrosser (Amsinckia douglasiana). Competition experiments were conducted in artificial stands composed of different mixtures of inbred and outbred progeny. The fitnesses of progeny were found to be significantly influenced by the composition of the competing neighborhood. The fitness of target plants, however, did not vary monotonically with the frequency of inbred plants in the neighborhood. Rather, for A. gloriosa, maximum performance was observed when there was an intermediate frequency of inbred neighbors. For A. douglasiana, the opposite pattern was found. The results suggest that competition among progeny has the potential to play a role in the selection of self-fertilization and possibly in the maintenance of mixed mating systems.
如果自花授粉产生的植物的竞争能力与异交产生的植物不同，那么近亲繁殖衰退的程度可能会受到竞争环境组成的影响（即，在表现出近亲繁殖衰退的“目标”植物附近，自交和异交产生的植物的频率）。在这里，我们报告了旨在研究近亲繁殖衰退是否受竞争邻域内自交植物频率影响的实验结果。研究了一年生植物琴颈草属的两个物种，一个几乎完全自交（壮丽琴颈草），另一个部分异交（道格拉斯琴颈草）。在由自交和异交后代的不同混合物组成的人工林分中进行了竞争实验。发现后代的适合度受到竞争邻域组成的显著影响。然而，目标植物的适合度并没有随着邻域内自交植物的频率单调变化。相反，对于壮丽琴颈草，当自交邻居的频率处于中间水平时，观察到最大表现。对于道格拉斯琴颈草，则发现了相反的模式。结果表明，后代之间的竞争有可能在自花受精的选择中发挥作用，并可能在混合交配系统的维持中发挥作用。
