RESUMO
This study tested the hypothesis that self-compatibility would be associated with floral traits that facilitate autonomous self-pollination to ensure reproduction under low pollinator visitation. In a comparison of two pairs of Ipomoea species with contrasting breeding systems, we predicted that self-compatible (SC) species would have smaller, less variable flowers, reduced herkogamy, lower pollinator visitation and higher reproductive success than their self-incompatible (SI) congeners. We studied sympatric species pairs, I. hederacea (SC)- I. mitchellae (SI) and I. purpurea (SC)-I. indica (SI), in Mexico, over two years. We quantified variation in floral traits and nectar production, documented pollinator visitation, and determined natural fruit and seed set. Hand-pollination and bagging experiments were conducted to determine potential for autonomous self-pollination and apomixis. Self-compatible Ipomoea species had smaller flowers and lower nectar production than SI species; however, floral variation and integration did not vary according to breeding system. Bees were primary pollinators of all species, but visitation rates were seven times lower in SC than SI species. SC species had a high capacity for autonomous self-pollination due to reduced herkogamy at the highest anther levels. Self-compatible species had two to six times higher fruit set than SI species. Results generally support the hypothesis that self-compatibility and autonomous self-pollination ensure reproduction under low pollinator visitation. However, high variation in morphological traits of SC Ipomoea species suggests they maintain variation through outcrossing. Furthermore, reduced herkogamy was associated with high potential for autonomous self-pollination, providing a reproductive advantage that possibly underlies transitions to self-compatibility in Ipomoea.
Assuntos
Flores , Ipomoea , Cruzamento , Flores/anatomia & histologia , Flores/fisiologia , Frutas/anatomia & histologia , Frutas/fisiologia , Ipomoea/anatomia & histologia , Ipomoea/fisiologia , México , Fenótipo , Polinização , Reprodução , Sementes/anatomia & histologia , Sementes/fisiologia , Autofertilização , SimpatriaRESUMO
The leaf anatomy of Cestrum acuminatissimum Dunal, C. alternifolium (Jacq.) O.E. Schulz, C. glabrescens (C.V. Morton) Steyerm. et Maguire, C. imbricatum Rusby, C. Iatifolium Lam., C. neblinense D'Arcy et Benítez, C. ruizteranianum Benítez et D'Arcy, C. schulzianum Francey, C. tillettii Benítez et D'Arcy y C. tubulosum Sendtner, is described in order to value its diagnostic characters useful as source of data in the taxonomy of the Solanaceae. The material was obtained from specimens deposited in MY herbarium, coming from different geographical areas of Venezuela, and it was prepared according the classical methodology used in leaf anatomy studies. The results obtained have, besides the common features mentions for other species of the genus Cestrum, some differences in: types and density of trichomes, thickness and sinuousities of the cell wall, stomata position, as well as in the distribution of esclerenchymatous cells of the mesophyll, midvein petiole.