Flowering phenology and plant-pollinator interactions in a grassland community of Southern Brazil

Abstract

Synchrony of phenological events at the community level is a critical aspect for plants. Distinct phenological patterns, such as aggregated and segregated, act in the establishment of plant-pollinator interactions and can play a fundamental role in plant community structure. Working in grazed subtropical grasslands in southern Brazil, our goals were to describe the plant-pollinator interactions in the grassland community and investigate the phenological patterns. The study was performed in a grassland community of Southern Brazil. In 12 sample plots (100m2 each) all flowering plant species with visually attractive flowers were recorded monthly during the period of six months. We used the Pianka index to estimate the flowering overlap, by comparison with 1000 pseudo-communities and a synchrony index to evaluate the phenological community pattern. All 82 flowering species present in the 12 study plots were observed monthly between six months. We observed that the community presented aggregated and non-synchronized flowering periods, which should reduce pollinator competition. We found no significant relationship between flowering synchrony and similarity of pollinators, that is, plant species that flower for a long time or together with many species did not share more pollinators than plants that flower for short time and alone. Some guilds of flowers visitors preferred flowers with a particular color, which indicated the important role of visual traits in plant-pollinator interactions. This study reports that flowering phenology could be structured by biotic components more than by random processes in these species-rich South Brazilian grasslands.