摘要
Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of line-age diversification.Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their con-sequences on reproductive components.A higher predictability of pollination syndromes is expected in dioecious species,which are dependent on pollinators,than in self-compatible hermaphroditic taxa.Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollina-tors,whereas no pollen limitation is expected in hermaphroditic spe-cies with autonomous self-pollination.Additionally,in the absence of pollen limitation,more or better seeds are expected in dioecious species,according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica,all endemic to Mexico,we first described flower phenol-ogy,flower production and longevity and nectar volume and concen-tration.Then,we evaluated the correspondence between floral visitors and pollination syndromes.In hermaphrodite plants,we determined the level of herkogamy and the potential for autonomous self-pollina-tion.Finally,we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important Findings In contrast to our prediction,dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites;however,male flowers exhib-ited a higher correspondence than female flowers.No pollen limitation was detected in dioecious species,for which visitation rate did not differ between male and female flowers.The her-maphroditic F.fulgens showed pollen limitation for seed number,despite the presence of autonomous selfing.Fruit set from auton-omous pollination was higher in F.arborescens,which showed a lower level of herkogamy compared with F.fulgens.Finally,dioecious species produced fewer but heavier seeds compared with hermaphrodite species.Although Fuchsia is classified as an outcrossing genus,both hermaphroditic species showed autono-mous self-pollination.The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization.This could play an important role in the evolution of dioecy;however,a comparative phylogenetic approach is required to confirm this hypothesis.
基金
This work was funded by a masters scholarship to A.A.-B.(no.270296)
a research grant to E.C.from the Consejo Nacional de Ciencia y Tecnología(CONACyT grant no.105952)
from the Universidad Michoacana de San Nicolás de Hidalgo.