Functional Morphology and Floral Odor of Ditassa burchellii (Apocynaceae, Asclepiadoideae), a Micromyiophilous Species from Southeastern Brazil

Premise of research. Studying functional floral morphology in Asclepiadoideae requires anatomical and histochemical analyses due to the complex synorganization and high diversity of secretory tissues in their flowers. Pollinators of the subfamily are poorly known in some genera, yet floral volatiles presumably play an important role in their attraction. Thus, we addressed the following questions: (1) Are the floral morphology and pollination mechanism of Ditassa burchellii (Asclepiadoideae, Metastelmatinae) similar to those of other Asclepiadoideae species? (2) Due to its minute, odoriferous flowers, are the pollinators equally minute and attracted by specific floral volatiles? (3) Does most pollinarium removal occur during the flowering peak and, consequently, floral volatile emission peak?Methodology. We studied flower morphology by light and scanning electron microscopies, identified pollinators, determined floral volatile composition by headspace analysis, and quantified pollinarium removal before, du...