Waser Nickolas M, Price Mary V
Department of Biology, University of California, Riverside, California, 92521.
Rocky Mountain Biological Laboratory, Crested Butte, Colorado, 81224.
Evolution. 1994 Jun;48(3):842-852. doi: 10.1111/j.1558-5646.1994.tb01366.x.
Depending on its genetic causes, outbreeding depression in quantitative characters may occur first in the free-living F generation produced by a wide cross. In 1981-1985, we generated F progenies by hand-pollinating larkspurs (Delphinium nelsonii) with pollen from 1-m, 3-m, 10-m, or 30-m distances. From the spatial genetic structure indicated by previous electrophoretic and reciprocal transplantation studies, we estimate that these crosses range from being inbred (f ≈ 0.06) to outbred. We planted 594 seeds from 66 maternal sibships under natural conditions. As of 1992, there was strong evidence for both inbreeding depression and outbreeding depression. Progeny from intermediate crossing distances grew approximately twice as large as more inbred or outbred progeny in the first 5 yr after planting (P = 0.013, repeated measures ANOVA), and survived almost 1 yr longer on average (contrast of 3-m and 10-m treatments versus 1 m and 30 m; P = 0.028, ANOVA). Twenty maternal sibships produced flowering individuals; only four and two of these represented 1-m and 30-m crossing distances, respectively (P = 0.021, G-test). The cumulative fitness of intermediate distance sibships averaged about twice that of 1-m sibships, and five to eight times that of 30-m sibships (P = 0.017, ANOVA). Thus, even though progeny of 1-m crosses were inbred to a degree only about one-eighth that of selling, inbreeding depression approximated 50%, and outbreeding depression equaled or exceeded 50% for all fitness components.
根据其遗传原因，数量性状的远交衰退可能首先出现在远缘杂交产生的自由生活的F1代中。1981年至1985年期间，我们用来自1米、3米、10米或30米距离的花粉对翠雀（纳尔逊翠雀）进行人工授粉，从而产生了F1代子代。根据先前的电泳和互交移植研究表明的空间遗传结构，我们估计这些杂交从近交（f≈0.06）到远交不等。我们在自然条件下种下了来自66个母系同胞组的594粒种子。截至1992年，有充分证据表明存在近交衰退和远交衰退。种植后的前5年，中等杂交距离的子代生长速度大约是近交或远交程度更高的子代的两倍（P = 0.013，重复测量方差分析），并且平均存活时间几乎长1年（3米和10米处理组与1米和30米处理组的对比；P = 0.028，方差分析）。20个母系同胞组产生了开花个体；其中只有4个和2个分别代表1米和30米的杂交距离（P = 0.021，G检验）。中等距离同胞组的累积适合度平均约为1米同胞组的两倍，是30米同胞组的五到八倍（P = 0.017，方差分析）。因此，尽管1米杂交的子代近交程度仅约为自交的八分之一，但所有适合度成分的近交衰退约为50%，远交衰退等于或超过50%。
