Norman Joanna K, Sarai Ann K, Weller Stephen G, Dawson Todd E
Department of Ecology and Evolutionary Biology, University of California, Irvine, California, 92717.
Section of Ecology and Systematics, Corson Hall, Cornell University, Ithaca, New York, 14853-2701.
Evolution. 1995 Apr;49(2):297-306. doi: 10.1111/j.1558-5646.1995.tb02242.x.
We compared inbreeding depression in hermaphroditic Schiedea lydgatei and its gynodioecious sister species, S. salicaria, to infer the level of inbreeding depression in their common ancestor. With measurements of selfing rates, this information can be used to assess the importance of inbreeding depression in the evolution of breeding systems in S. lydgatei and S. salicaria. Morphological and physiological characters related to fitness were compared for inbred and outcrossed S. lydgatei in high- and low-fertilizer environments in the greenhouse. Seed mass, number of seeds per capsule, germination, survival, biomass, number of flowers, and age at first flowering were compared for inbred versus outcrossed progeny. We also measured inbreeding depression in maximal rates of photosynthetic carbon assimilation and stomatal conductance to water vapor, traits that affect fitness through their influence on plant carbon balance and water-use efficiency (ratio of carbon gain to water loss). All traits except number of seeds per capsule in parents and survival showed inbreeding depression, with the magnitude depending on family and environment. High inbreeding depression is likely in the ancestor of S. lydgatei and S. salicaria, indicating that, with sufficiently high selfing rates, females could spread in populations. Hermaphroditism in S. lydgatei is probably favored by low selfing rates. In contrast, the evolution of gynodioecy in S. salicaria apparently has been favored by relatively high selfing rates in combination with high inbreeding depression.
我们比较了雌雄同体的利德盖特氏Schiedea lydgatei及其雌全异株的近缘物种柳叶Schiedea salicaria的近亲繁殖衰退情况，以推断它们共同祖先的近亲繁殖衰退水平。通过测量自交率，这些信息可用于评估近亲繁殖衰退在利德盖特氏Schiedea lydgatei和柳叶Schiedea salicaria繁殖系统进化中的重要性。在温室中，我们比较了在高肥力和低肥力环境下自交和异交的利德盖特氏Schiedea lydgatei与适合度相关的形态和生理特征。比较了自交和异交后代的种子质量、每蒴果种子数、发芽率、存活率、生物量、花的数量和首次开花年龄。我们还测量了光合碳同化最大速率和气孔导度对水蒸气的近亲繁殖衰退情况，这些性状通过影响植物碳平衡和水分利用效率（碳增益与水分损失之比）来影响适合度。除了亲本的每蒴果种子数和存活率外，所有性状都表现出近亲繁殖衰退，其程度取决于家系和环境。利德盖特氏Schiedea lydgatei和柳叶Schiedea salicaria的祖先可能存在高度的近亲繁殖衰退，这表明，在自交率足够高的情况下，雌性个体可以在种群中扩散。利德盖特氏Schiedea lydgatei的雌雄同体现象可能因自交率低而受到青睐。相比之下，柳叶Schiedea salicaria的雌全异株进化显然受到相对较高的自交率和高度近亲繁殖衰退的共同青睐。
