Mudanças morfológicas e funcionais das flores de Guazuma ulmifolia (Malvaceae) e a dinâmica de visitantes florais

Abstract

Floral attractives are fundamental for pollinators to approach the flowers and visit them. In entomophilous pollination, a lot of plants developed odors as floral attractive traits, as insects have a specialized olfactory system and utilize it for a range of functions. The odors are produced by osmophores, secretory glands that produces volatiles compounds. It is already known that odorant substances constitute an important element in pollination process. However, the dynamic of odor release by osmophores and how it affects floral attractiveness for floral visitors still constitute a knowledge blank. Guazuma ulmifolia Lam. flowers have a strong fragrance that seems to vary over time. Furthermore, its reproductive structures are found in separated chambers, whose access is formed by tiny entrances. The female chamber entrance is surrounded by petal appendages, which can vary in position during the floral lifetime, releasing or blocking the chamber access. In this context, G. ulmifolia is a good model as a study object to respond how the floral morphology and odor release variation affects the frequency, composition and behavior of floral visitors. Observations of floral morphologic changes, neutral red tests and gas chromatography were made to understand morphologic and odor release variation in flowers. To evaluate frequency, composition and behavior of visitors, were made observations, captures, measurements and identifications of insects. The results showed that the highest release of attraction-related odors occur in the second day of floral life, which coincides with the full expansion of the floral appendages and with the highest frequency and richness of visitors, indicating that the odor act as an important floral attractive in this species. Female and male chambers have a distinct visitor composition in terms of body size, which shows that the chambers access size act as a limiting factor to the visits. The behavioral, frequency and chambers accessibility results showed that tiny Diptera and Chalcidoidea wasps form the potential pollinator group of G. ulmifolia.