Am J Bot. 1998 May;85(5):661.
Inbreeding may influence the intensity of sibling competition by altering the number of offspring produced or by changing plant morphology in ways that influence seed dispersion patterns. To test this possibility, effects of inbreeding on seed production and on traits that influence progeny density were measured using experimental pollinations of flowers of Cakile edentula var. lacustris. Different flowers on a plant were either hand pollinated with self pollen (with and without emasculation) or foreign pollen, or they were allowed to be pollinated naturally. Selfed flowers matured significantly fewer viable seeds than outcrossed flowers (10.3% less seed maturation with inbreeding depression of 19.2%), due in large part to a greater percentage of proximal seed abortions and lower germination success. Plants grown from selfed seeds tended to have lower seed production (37 fewer seeds on average, with inbreeding depression of 16.2%), caused in part by an increase in the percentage of fruits with proximal seed abortions, although this effect was not significant. Inbreeding depression in total fitness was 29.0%, which corresponds to a difference of 46 seeds per pollinated ovule. Selfing rate estimates were usually intermediate to high, indicating that inbreeding effects observed in this study would be present in naturally pollinated progeny. Although the influence of inbreeding directly on dispersal was negligible, the predicted reduction in sibling competition caused by reduced seed production resulted in an estimate of inbreeding depression of 17.5%, which is 11.5% lower than that measured under uniform conditions. Consequently, inbreeding depression estimated under natural dispersion patterns may be lower than that estimated under uniform conditions since seeds from self- and cross-pollination may not experience the same competitive environment in the field. Inbreeding in the maternal generation, therefore, could influence progeny fitness not only by determining the genetic composition of progeny, but also by influencing the competitive environment in which progeny grow.
近亲繁殖可能通过改变后代的数量或通过改变影响种子散布模式的植物形态来影响同胞竞争的强度。为了验证这种可能性，通过对 Cakile edentula var. lacustris 的花进行实验授粉，测量了近亲繁殖对种子产生和影响后代密度的性状的影响。植物上的不同花朵要么用自花花粉（去雄和不去雄）或异花花粉进行人工授粉，要么让其自然授粉。自花授粉的花朵成熟的可育种子明显少于异花授粉的花朵（自交衰退 19.2%，种子成熟度降低 10.3%），这主要是由于近端种子败育的比例较大和发芽成功率较低。自交种子长出的植物种子产量往往较低（平均少 37 粒种子，自交衰退 16.2%），部分原因是近端种子败育的果实比例增加，尽管这种影响不显著。总适合度的自交衰退率为 29.0%，这相当于每授粉的胚珠减少 46 粒种子。自交率的估计值通常介于中间到高，这表明本研究中观察到的自交效应将存在于自然授粉的后代中。尽管近亲繁殖对散布的直接影响可以忽略不计，但由于种子产量减少导致同胞竞争减少，预计自交衰退率为 17.5%，比均匀条件下测量的自交衰退率低 11.5%。因此，由于自花授粉和异花授粉的种子在田间可能不会经历相同的竞争环境，因此在自然散布模式下估计的自交衰退率可能低于在均匀条件下估计的自交衰退率。因此，母本世代的近亲繁殖不仅可以通过决定后代的遗传组成，还可以通过影响后代生长的竞争环境来影响后代的适合度。
