Reproductive biology of woody species in Caatinga, a dry forest of northeastern Brazil

摘要

Studies concerning reproductive biology at the community level have not yet been reported for Caatinga. In this study, we analyzed the flowering phenology, floral longevity, and breeding system of 15 typical woody species in this ecosystem. Flowering occurred mostly during the dry season for ten species. Among dioecious plants, male individuals predominate for two out of three species analyzed. In May-tenus rigida, a gynodioecious species, female individuals predominate in the population; the number of flowers per inflorescence is the same between hermaphrodite (14.0 ± 4.4) and female (14.8 ± 4.6) individuals, but significant differences are found with respect to fruit set by hermaphrodite (1.9 ± 0.9) and pistillate flowers (4.0 ± 2.4). Self-compatibility occurs in 26.7% of the studied species, whereas 73.3% present obligatory xenogamy. Among self-incompatible species, two have a stylar site of rejection, while self-pollen tubes reach the ovules in five. Late-acting self-incompatibility in Sideroxylon obtusifolium constitutes the first record of this mechanism in Sapotaceae. The majority of the species studied have a lower fruit/flower than seed/ovule ratio. Reproduction of woody plants in this arid ecosystem depends upon biotic vectors that can promote cross-pollination and gene flow.