Facultad de Biología, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México.
Plant Biol (Stuttg). 2014 Nov;16(6):1096-103. doi: 10.1111/plb.12161. Epub 2014 Mar 14.
In subdioecious populations, functional female, male and hermaphrodite individuals coexist. Subdioecy may be a transitional state towards dioecy or a breakdown of dioecy, although lability in sex expression may maintain subdioecy as a stable condition. To better understand the ecological aspects involved in sex ratio dynamics and breeding system evolution, we studied the pollination and female fitness components of female and hermaphrodite individuals of the subdioecious shrub Fuchsia microphylla. In two natural populations at the Trans-Mexican Volcanic Belt we estimated female frequency and several reproductive components of female and hermaphrodite plants under natural pollination and experimental pollination treatments. Average female frequency was 42%, and on average, 42.5% of hermaphrodites produced fruits. Female plants showed a 17-fold female fertility advantage over hermaphrodites through increased fruit production, as the number of seeds and germination rates did not differ between morphs. Hermaphrodite flowers were larger, with similar nectar production and concentration to female flowers, and pollinators did not show consistent morph preferences. Some hermaphrodites produced fruits autonomously, and female flowers excluded from pollinators produced fruits putatively by apomixis. Fruit production in hermaphrodites, but not in females, was related to height, suggesting increased investment of hermaphrodites in the female function at higher resource status. For sex ratios to be at equilibrium, the female fertility advantage should be reduced about eightfold. However, it may be that hermaphrodites are maintained by producing fruits at no cost to the male function at higher resource status, as the gender plasticity hypothesis proposes.
在雌雄异株的种群中，功能性雌性、雄性和雌雄同体个体共存。雌雄同体可能是向雌雄异株过渡的状态，或者是雌雄异株的崩溃，尽管性别表达的不稳定性可能使雌雄同体保持稳定状态。为了更好地理解涉及性别比例动态和繁殖系统进化的生态方面，我们研究了雌雄异株灌木紫苿莉的雌性和雌雄同体个体的传粉和雌性适合度组成。在跨墨西哥火山带的两个自然种群中，我们在自然传粉和实验传粉处理下估计了雌性频率和雌性和雌雄同体植物的几个繁殖组成部分。雌性频率的平均值为 42%，平均而言，42.5%的雌雄同体产生果实。通过增加果实产量，雌性植物比雌雄同体具有 17 倍的雌性生育力优势，因为雌雄同体的种子数量和萌发率与形态之间没有差异。雌雄同体花的花朵较大，花蜜产量和浓度与雌性花相似，传粉者没有表现出一致的形态偏好。一些雌雄同体自主产生果实，而被传粉者排除的雌性花可能通过无融合生殖产生果实。雌雄同体的果实产量，但不是雌性的，与高度有关，这表明雌雄同体在较高资源状态下对雌性功能的投资增加。为了使性别比例达到平衡，雌性生育力优势应该降低约八倍。然而，根据性别可塑性假说，雌雄同体可能通过在较高资源状态下不牺牲雄性功能来维持果实的产生。
