McCall Claire, Waller Donald M, Mitchell-Olds Tom
Department of Biology, Trinity University, 715 Stadium Drive, San Antonio, Texas, 78212.
Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin, 53706.
Evolution. 1994 Jun;48(3):818-827. doi: 10.1111/j.1558-5646.1994.tb01364.x.
Studies of inbreeding depression in wild plants customarily compare the fitness of outcrossed progeny to progeny derived from one generation of self-pollination. We compare levels of inbreeding depression in a greenhouse in two populations of jewelweed using progeny derived from random outcrosses, one generation of self-pollination, and three generations of selling. The progeny have expected inbreeding coefficients of, respectively, 0, 0.5, and 0.875. Seedling survivorship declined linearly with the level of inbreeding in both populations. Inbreeding also increased the variability of emergence date. Maternal family membership affected early seedling performance and often interacted significantly with the level of inbreeding. In contrast, path analyses reveal that inbreeding had both negative linear and positive quadratic direct effects on seed and final plant weight, causing the highly inbred progeny to outperform progeny derived from one generation of selfing. These results suggest either the rapid purging of deleterious alleles or diminishing epistasis among the loci affecting these characters. It is not clear why the loci affecting survival responded differently.
对野生植物近亲繁殖衰退的研究通常会比较异交后代与自花授粉一代产生的后代的适合度。我们在温室中，使用随机异交、自花授粉一代和连续三代自交产生的后代，比较了两个凤仙花种群的近亲繁殖衰退水平。这些后代预期的近交系数分别为0、0.5和0.875。在两个种群中，幼苗存活率均随近亲繁殖水平呈线性下降。近亲繁殖还增加了出苗日期的变异性。母系家族成员影响幼苗早期表现，且常常与近亲繁殖水平产生显著交互作用。相比之下，通径分析表明，近亲繁殖对种子和最终植株重量既有负向线性直接效应，也有正向二次直接效应，导致高度自交的后代表现优于自花授粉一代产生的后代。这些结果表明，有害等位基因被迅速清除，或者影响这些性状的基因座之间的上位性效应减弱。目前尚不清楚影响存活的基因座为何会有不同反应。
