父母之间的亲缘关系会降低自然种群中短柱杜鹃后代的适合度。
Kinship between parents reduces offspring fitness in a natural population of Rhododendron brachycarpum.
机构信息
Institute of Mountain Science, Shinshu University, Matsumoto 390-8621, Japan.
出版信息
Ann Bot. 2010 Apr;105(4):637-46. doi: 10.1093/aob/mcq018. Epub 2010 Mar 3.
BACKGROUND AND AIMS
A reduction in offspring fitness resulting from mating between neighbours is interpreted as biparental inbreeding depression. However, little is known about the relationship between the parents' genetic relatedness and biparental inbreeding depression in their progeny in natural populations. This study assesses the effect of kinship between parents on the fitness of their progeny and the extent of spatial genetic structure in a natural population of Rhododendron brachycarpum.
METHODS
Kinship coefficients between 11,858 pairs of plants among a natural population of 154 R. brachycarpum plants were estimated a priori using six microsatellite markers. Plants were genotyped, and pairs were selected from among 60 plants to vary the kinship from full-sib to unrelated. After a hand-pollination experiment among the 60 plants, offspring fitness was measured at the stages of seed maturation (i.e. ripening) under natural conditions, and seed germination and seedling survival under greenhouse conditions. In addition, spatial autocorrelation was used to assess the population's genetic structure.
KEY RESULTS
Offspring fitness decreased significantly with increasing kinship between parents. However, the magnitude and timing of this effect differed among the life-cycle stages. Measures of inbreeding depression were 0.891 at seed maturation, 0.122 (but not significant) at seed germination and 0.506 at seedling survival. The local population spatial structure was significant, and the physical distance between parents mediated the level of inbreeding between them.
CONCLUSIONS
The level of inbreeding between individuals determines offspring fitness in R. brachycarpum, especially during seed maturation. Genetic relatedness between parents caused inbreeding depression in their progeny. Therefore, biparental inbreeding contributes little to reproduction and instead acts as a selection force that promotes outcrossing, as offspring of more distant (less related) parents survive better.
背景与目的
由于双亲的近交，导致后代适应度降低，这被解释为双亲亲本的近交衰退。然而，对于自然种群中父母的遗传亲缘关系与后代的双亲亲本近交衰退之间的关系，人们知之甚少。本研究评估了父母亲缘关系对其后代适应性的影响，并评估了自然种群中短柄杜鹃的空间遗传结构的程度。
方法
使用 6 个微卫星标记，预先估计了自然种群中 154 株短柄杜鹃植物中 11858 对植物的亲缘系数。对植物进行基因型检测，并从 60 株植物中选择亲缘关系从全同胞到无关的配对。在 60 株植物的人工授粉实验之后，在自然条件下测量种子成熟（即成熟）阶段的后代适应性，以及温室条件下的种子萌发和幼苗存活率。此外，还使用空间自相关来评估种群的遗传结构。
结果
后代适应性随双亲亲缘关系的增加而显著下降。然而，这种效应的大小和时间在生命周期的不同阶段有所不同。种子成熟阶段的近交衰退程度为 0.891，种子萌发阶段为 0.122（但不显著），幼苗存活率阶段为 0.506。局部种群空间结构显著，父母之间的物理距离调节了它们之间的近交程度。
结论
个体之间的近交程度决定了短柄杜鹃的后代适应性，特别是在种子成熟阶段。父母之间的遗传亲缘关系导致了其后代的近交衰退。因此，双亲亲本的近交对繁殖的贡献较小，反而成为促进异交的选择力，因为来自较远（亲缘关系较低）父母的后代存活率更高。
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