Osmóforos de Guazuma ulmifolia Lam. (Malvaceae): estrutura, funcionalidade e interações com visitantes florais

Abstract

Many interactions between plants and pollinators are mediated by floral Volatile Organic Compounds (VOCs). Those compounds may be produced by specialized glands called osmophores, they play an important role in the attraction of pollinators. However, little attention has been paid to the functionality of the osmophores and its relation to the temporal variation of the floral VOCs secreted by them. To understand how the variation of the floral morphology and the release of scents by the osmophores affect the abundance, composition and behavior of floral visitor insects, this study used the flowers of Guazuma ulmifolia Lam. (Malvaceae) as a model. To evaluate the variation of morphology and release of floral scents, observations of changes in floral morphology, anatomic and histochemical analysis and gas chromatography were made. Data of abundance, composition and floral visitors’ behavior were collected, and insects were captured, measured and identified. The results show that the biggest release of compounds related to the attractions of insects happens on the second day of anthesis, which also corresponds to the day with the highest frequency and species richness. The male and female chambers show a distinct composition of visitors in relation to the body size. The results indicate that the scent acts as an important floral trait and the size of the access to the chamber acts as a limiting factor to the visitation. The results of behavior, abundance and acessibility of floral chambers has shown that small insects (Diptera, Coleoptera and Chalcidoidea wasps) are the pollinators of G. ulmifolia, therefore, it can be included in the SDI pollination system.