Flower-Visiting Insects and Phenology ofLippia alba(Lamiales: Verbenaceae): Floral Color Changes and Environmental Conditions as Cues for Pollinators

Abstract

Lippia alba (Mill.) N.E. Br. ex Britton & P. Wilson (Verbenaceae) is a herbal aromatic shrub with medicinal properties. Natural populations of this species are allogamous and self-incompatible. Therefore, this plant species relies on pollinators to outcross and maintain the genetic variability. Here, we investigated the floral phenology, pollen morphology, the floral visitor entomofauna, and the influence of climatic factors on the frequency of visits in L. alba flowers. The study was conducted at Federal University of Juiz de Fora Plant Experimental Area, southeast Brazil. The flowering of L. alba occurred throughout the whole year. The anthesis is diurnal and lasts 5 d. The nectar guide was visible from the onset of flowering until the third day. Pollen grains were classified as isopolar, oblate spheroidal, three-colporate (rare, four-colporate), surface tectate-perforate, and endoaperture lalongate, with median constriction. Insects from the order Hymenoptera were the most frequent visitors observed, followed by Lepidoptera, Thysanoptera, Diptera, and Hemiptera-Heteroptera. The preference of insects for flowers with nectar guides shows that the color is likely to be an important visual trait to increase the frequency of visits. Moreover, the climate variables temperature, relative humidity, wind speed, and light were important to define the composition of the most frequent floral visitors.