Griffin Celine A M, Eckert Christopher G
Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Evolution. 2003 Jul;57(7):1513-9. doi: 10.1111/j.0014-3820.2003.tb00359.x.
Localized dispersal and mating may genetically structure plant populations, resulting in matings among related individuals. This biparental inbreeding has significant consequences for the evolution of mating systems, yet is difficult to estimate in natural populations. We estimated biparental inbreeding in two populations of the largely self-fertilizing plant Aquilegia canadensis using standard inference as well as a novel experiment comparing apparent selfing between plants that were randomly relocated within populations to experimental control plants. Using two allozyme markers, biparental inbreeding (b) inferred from the difference between single-locus and multilocus estimates of selfing (b = s(s) - s(m)) was low. Less than 3% of matings involved close relatives (mean b = 0.029). In contrast, randomly relocating plants greatly reduced apparent selfing (mean s(s) = 0.674) compared to control plants that had been dug up and replanted in their original locations (s(s) = 0.953, P = 0.002). Based on this difference in s(s), we estimated that approximately 30% of all matings involved close relatives (mean b = 0.279, 95% CL = 0.072-0.428). Inference from s(s) - s(m) underestimated b in these populations by more than an order of magnitude. Biparental inbreeding is thought to influence the evolution of self-fertilization primarily through reducing the genetic cost of outcrossing. This is unlikely to be of much significance in A. canadensis because inbreeding depression (a major cost of selfing) is much stronger than the cost of outcrossing. However, biparental inbreeding combined with strong inbreeding depression may influence selection on dispersal.
局部扩散和交配可能会在基因层面上构建植物种群结构，导致亲缘个体间的交配。这种双亲近亲繁殖对交配系统的进化具有重大影响，但在自然种群中却难以估算。我们使用标准推断方法以及一项新颖的实验，来估计两种主要自花受精植物加拿大耧斗菜种群中的双亲近亲繁殖情况。该实验比较了在种群内随机重新安置的植物与实验对照植物之间的表观自交情况。使用两种等位酶标记，从自交单基因座估计值与多基因座估计值之间的差异推断出的双亲近亲繁殖率（b = s(s) - s(m)）较低。不到3%的交配涉及近亲（平均b = 0.029）。相比之下，与那些被挖出并重新种植在原位置的对照植物（s(s) = 0.953，P = 0.002）相比，随机重新安置植物极大地降低了表观自交率（平均s(s) = 0.674）。基于s(s)的这种差异，我们估计大约30%的交配涉及近亲（平均b = 0.279，95%置信区间 = 0.072 - 0.428）。在这些种群中，从s(s) - s(m)推断出的双亲近亲繁殖率比实际值低了一个数量级以上。双亲近亲繁殖被认为主要通过降低异交的遗传成本来影响自花受精的进化。这在加拿大耧斗菜中不太可能具有重要意义，因为近亲繁殖衰退（自交的主要成本）比异交成本要强得多。然而，双亲近亲繁殖与强烈的近亲繁殖衰退相结合，可能会影响对扩散的选择。
