Chen Jianguo, Niu Yang, Li Zhimin, Yang Yang, Sun Hang
Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.
School of Life Sciences, Yunnan Normal University, Kunming, Yunnan, China.
Plant Reprod. 2017 Jun;30(2):107-117. doi: 10.1007/s00497-017-0303-4. Epub 2017 Jun 8.
Sex allocation in Cyananthus delavayi. Gynodioecy, where females and hermaphrodites coexist in the same natural population, is particularly suitable for predicting the ecological pressures that drive the stability of gender polymorphism. Since females have a disadvantage in that they only contribute to the next generation via ovules, they should gain an advantage via other means, of which resource allocation is an important component. Thus, to study their sex allocation is very helpful to understand how the dimorphic sexual system is maintained in natural systems. We studied the sex allocation patterns and reproductive output of the gynodioecious Cyananthus delavayi in three populations with different soil qualities (organic matter, N, P and K). The hermaphroditic flowers and pistils were much larger than those of female individuals. Although both gender morphs invested similar biomass in the pistils, females allocated more of their resource pool to the seed production, while hermaphrodites allocated more to pollinator advertisement. The pollen production of hermaphrodites did not differ between populations, suggesting that pollen production by hermaphrodites was not limited by soil nutrients. Fruit set of females, but not hermaphrodites, decreased with declining soil quality, whereas seeds per fruit of both females and hermaphrodites were highest in poor soils. Overall, this study shows that females achieve greater reproductive success by allocating more of their resource pool to enhancing seed production, which should favor their presence in gynodioecious populations. The hermaphrodites achieve reproductive success from both pollen and seed production, and unnecessarily reduce their allocation to pollen production. Soil quality should explain, at least partially, the sexual allocation patterns. Furthermore, some of our findings contradict previous hypotheses, thus adding a new example to the body of research on plant sex allocation and the development of future theories.
滇川蓝钟花的性别分配。雌全同株现象，即雌性个体和雌雄同体个体共存于同一自然种群中，特别适合用于预测驱动性别多态性稳定性的生态压力。由于雌性个体存在劣势，即它们仅通过胚珠对下一代有贡献，所以它们应通过其他方式获得优势，其中资源分配是一个重要组成部分。因此，研究它们的性别分配对于理解自然系统中双态性性系统如何维持非常有帮助。我们研究了生长在三种不同土壤质量（有机质、氮、磷和钾）的种群中，具有雌全同株现象的滇川蓝钟花的性别分配模式和繁殖输出。雌雄同体花和雌蕊比雌性个体的要大得多。尽管两种性别形态在雌蕊上投入的生物量相似，但雌性将更多的资源库分配给种子生产，而雌雄同体则将更多资源分配给传粉者吸引。雌雄同体的花粉产量在不同种群间没有差异，这表明雌雄同体的花粉生产不受土壤养分限制。雌性个体的坐果率随土壤质量下降而降低，而雌雄同体个体则不然，不过雌性和雌雄同体的单果种子数在贫瘠土壤中都是最高的。总体而言，这项研究表明，雌性通过将更多的资源库分配用于提高种子产量来实现更大的繁殖成功，这应该有利于它们在雌全同株种群中的存在。雌雄同体从花粉和种子生产中都能实现繁殖成功，且无需减少对花粉生产的分配。土壤质量至少应部分解释性别分配模式。此外，我们的一些发现与先前的假设相矛盾，从而为植物性别分配研究和未来理论发展增添了一个新例子。
