Ecologia reprodutiva de espécies de Callisthene e Qualea (Vochysiaceae): aborto, poliembrionia e predação de sementes

Abstract

The ability of plants to reproduce and generate fertile siblings apt to establish themselves in the environment is influenced by different factors, some of them intrinsic to their morphophysiology or external biological or physical agents. Hence, the reproductive success of a plant species is directly linked with the progenie and the factors that affect its quantity and quality. The Vochysiaceae is a family widely distributed in the Cerrado biome and is an important group to study from the ecological point of view. The reproductive ecology of four Vochysiaceae species was studied here with a focus on seed production. Factors affecting occurrence and frequency of abortion, seed predation and polyembryony were studied for different populations of Callisthene fasciculata, C. major, Qualea multiflora and Q. parviflora. The occurrence of polyembryony, abortion and pre-dispersal predation was quantified for mature seeds collected in different areas in order to characterize differences between genera, species, study areas and individuals. The occurrence of polyembryony and seed abortion was described using histological analysis of seeds in early stages of development of Q. multiflora and Q. parviflora. Polyembryony was transient and non-functional, resulting in mature seeds mostly monoembryonic. Embryo selection should have occurred in very early stages of embryogenesis, probably soon after fertilization, and polyembryony possibly function as a reproductive compensation strategy, selecting a potentially fitter embryo in detriment of the others. All species and populations presented seed abortion. Seed abortion differences in the studied species of Callisthene and Qualea were mostly related to intrinsical reproductive features and not with area or other factors. Seed initial growth analysis indicated some histological features, which are related to seed abortion. Undiferentiated teguments and inactivation of the hypostase signal the early stages of seed abortion. In contrast, seed predation not only varied between species, but also between areas and between individuals inside each species. Only C. fasciculata did not present seed predation. Larvae of insects were observed during histological analysis of early stages of Q. parviflora seed development, located between the testa and internal integument layers. We observed a different pattern of predation between genders, in Qualea species of insects were found inside the seeds, while in Callisthene major predators were found outside the seed. Abortion and seed predation undertake important part of the progeny of the species studied Vochysiaceae.