Pollination efficiency by bee guilds (Hymenoptera: Apoidea) to annatto flowers, Bixa orellana L.1753 (Bixaceae)

Abstract Insect’s pollination is essential in the maintaining of species abundance and diversity in the biomes. Bees are the most common pollinators of flowering plants, being their services very important in the conservation of biotope and biodiversity. The aims of this paper, are: to know the bee diversity and their population patterns over annatto flowers in the orchard; evaluate seed production in annatto plants with and without entomophilous pollination; to compare whether body size and intertegular distance of bees visiting annatto flowers correlates, and whether size of floral visitor bees in annatto influence in the pollination and productivity. During a flowering season in Dourados, Mato Grosso do Sul state, Brazil, 240 flower buds were chosen from five different plants and divided into six groups. In each group had 40 flower buds in the pre-anthesis phase (treatments): T1 (control), T2 (natural self-pollination), T3 (Anemophilous pollination), T4 (Big bees), T5 (Medium bees) and T6 (Small bees). Bee species were identified and measured by two metrics: body size (BS) and intertegular distance (ITD) to categorize their guilds. The treatments considered in the population’s analyses were the following: species richness, constancy, frequency, dominance of each bee species, and if bee size would influence in the process of annatto pollination. The analysis of variance was determined by the Tukey and Kruskal-Wallis tests (P < 0.05) for the population parameters. Floral visitor bee species in B. orellana were divided into two groups according to the periods of their activity: 6h-9h and 14h-18h, and in four guilds, based in their body size. Bees recorded from 6h to 9h were responsible for higher efficiency in the pollination rate; represented by the following species: Bombus morio, Centris sponsa, Centris fuscata; Epicharis flava, Epicharis affinis, Epicharis analis, Euglossa sp., Eulaema nigrita, Geotrigona mombuca, Melipona quadrifasciata, Hylaeus sp., and Pseudaugochlora graminea. Seed production was higher in the control (free access to all combined floral visitor), followed by big bees, and medium bees. The two metrics: (BS and ITD) has significant positive correlation. Big body species were more successful in the pollination of B. orellana.