Schmitt Johanna, Gamble Susan E
Graduate Program in Ecology and Evolutionary Biology, Box G- W301, Brown University, Providence, RI, 02912, USA.
Evolution. 1990 Dec;44(8):2022-2030. doi: 10.1111/j.1558-5646.1990.tb04308.x.
If microgeographic variation in selection within a natural plant population has resulted in local adaptation, then offspring fitness should decline with distance from the parental site. If outcrossed progeny are less well-adapted to the parental environment than inbred progeny, but perform better in environments different from that of the parent, then the fitness of inbred progeny relative to outcrossed progeny should decrease with dispersal distance from the parent. To test these predictions, we collected seedlings at 10-m intervals from a 40 times 40-m permanent grid in a natural population of Impatiens capensis, grew them in a greenhouse, and crossed them to produce outcrossed chasmogamous seeds. Seedlings from outcrossed chasmogamous and self-fertilized cleistogamous seeds were planted back into the source population in the original site of their maternal parents and in arcs 3 and 12 m from the parental location and censused weekly for survival and reproduction. The fitness of inbred offspring declined significantly and the magnitude of observed inbreeding depression increased with distance from the parental site, supporting the local adaptation hypothesis.
如果自然植物种群内选择的微地理变异导致了局部适应，那么子代适合度应随着与亲本地点距离的增加而下降。如果异交子代不如自交子代适应亲本环境，但在与亲本不同的环境中表现更好，那么自交子代相对于异交子代的适合度应随着与亲本的扩散距离而降低。为了检验这些预测，我们在凤仙花自然种群的一个40×40米的永久网格中，每隔10米收集一次幼苗，在温室中种植它们，并让它们杂交以产生异交的开花种子。将异交开花种子和自交闭花受精种子的幼苗重新种植到其母本亲本的原地点以及距离亲本位置3米和12米的弧线上的源种群中，每周对其存活和繁殖情况进行统计。自交子代的适合度显著下降，且观察到的近交衰退程度随着与亲本地点距离的增加而增加，这支持了局部适应假说。
