Polinização de Peixotoa tomentosa A. Juss. (Malpighiaceae), como as estruturas florais condicionam a visitação biótica e o transporte polínico

Abstract

Plant populations have undergone substantial changes over time due to anthropogenic and climatic factors. Angiosperms are the largest and most diverse plant group and have, accordingly, established extensive mutualistic interactions with insects. In the Cerrado, plant–insect interactions are highly diverse, and among the most relevant in this context are those involving the family Malpighiaceae, one of the 11 botanical families that produce floral oils. We investigated how floral morphology in one of its species, Peixotoa tomentosa A. Juss., affects bee visitation and fruit set, considering its capacity to produce fruit through agamospermy. The study was conducted in a Cerrado fragment at Itororó Park Club (formerly Clube de Caça e Pesca Itororó), in Uberlândia, Minas Gerais, Brazil. We assessed floral attractiveness to small-, medium-, and large-bodied bees and the resulting fruit set, and tested five controlled pollination treatments. Visitation rate was lower than expected, with only 10 bees recorded over 15 hours of observation, which limited the evaluation of the floral attraction and fruit set hypotheses; this did not, however, preclude comparison among pollination treatments, whose fruit set values were statistically similar, indicating reproductive capacity even in the absence of pollen grains. Although the adhesive function of staminodes has previously been reported in other plant families, our study provides the first confirmation of this function within Malpighiaceae, showing that the substance exuded by the staminodes significantly increases pollen grain adherence to the transport vector and, subsequently, to the stigmas. Studies on the chemical composition of the staminodal secretion may help elucidate its adhesive function. These results suggest a relationship between low pollinator frequency, prior anthropogenic disturbance (e.g., the 2021 fire), and reduced fruit set, reinforcing the importance of long-term studies on pollination in the Cerrado.