Ferriol M, Pichot C, Lefèvre F
Instituto Agroforestal Mediterráneo (IAM), Universidad Politécnica de Valencia, Camino de Vera, Valencia, Spain.
Heredity (Edinb). 2011 Jan;106(1):146-57. doi: 10.1038/hdy.2010.45. Epub 2010 Apr 28.
We investigated the variation and short-term evolution of the selfing rate and inbreeding depression (ID) across three generations within a cedar forest that was established from admixture ca 1860. The mean selfing rate was 9.5%, ranging from 0 to 48% among 20 seed trees (estimated from paternally inherited chloroplast DNA). We computed the probability of selfing for each seed and we investigated ID by comparing selfed and outcrossed seeds within progenies, thus avoiding maternal effects. In all progenies, the germination rate was high (88-100%) and seedling mortality was low (0-12%). The germination dynamics differed significantly between selfed and outcrossed seeds within progenies in the founder gene pool but not in the following generations. This transient effect of selfing could be attributed to epistatic interactions in the original admixture. Regarding the seedling growth traits, the ID was low but significant: 8 and 6% for height and diameter growth, respectively. These rates did not vary among generations, suggesting minor gene effects. At this early stage, outcrossed seedlings outcompeted their selfed relatives, but not necessarily other selfed seedlings from other progenies. Thus, purging these slightly deleterious genes may only occur through within-family selection. Processes that maintain a high level of genetic diversity for fitness-related traits among progenies also reduce the efficiency of purging this part of the genetic load.
我们研究了一片约于1860年由混合种子建立的雪松林内三代间自交率和近交衰退（ID）的变化及短期演变。平均自交率为9.5%，在20株母树上，自交率范围为0至48%（根据父系遗传的叶绿体DNA估算）。我们计算了每粒种子的自交概率，并通过比较子代中自交和杂交种子来研究近交衰退，从而避免母体效应。在所有子代中，发芽率很高（88 - 100%），幼苗死亡率很低（0 - 12%）。在奠基者基因库的子代中，自交和杂交种子的发芽动态存在显著差异，但在后续世代中没有差异。这种自交的短暂效应可能归因于原始混合物中的上位性相互作用。关于幼苗生长性状，近交衰退较低但显著：高度和直径生长的近交衰退分别为8%和6%。这些比率在各代之间没有变化，表明基因效应较小。在这个早期阶段，杂交幼苗比它们的自交亲属更具竞争力，但不一定比其他子代的自交幼苗更具竞争力。因此，清除这些轻微有害基因可能仅通过家系内选择发生。在子代中维持与适合度相关性状的高水平遗传多样性的过程，也降低了清除这部分遗传负荷的效率。
