Environmental windows for foraging activity in stingless bees, Melipona subnitida Ducke and Melipona quadrifasciata Lepeletier (Hymenoptera: Apidae: Meliponini)

Abstract

The foraging success of a bee species is limited to an environmental window, a combination of optimal ambient temperatures and resource availability. Mismatches between flowering and optimal foraging temperature may lead to a reduction of a colony's food intake and, eventually, of brood production. In the present study, we evaluated the pollen foraging activity of two native Brazilian meliponine species Melipona quadrifasciata and M. subnitida at the campus of the University of Sao Paulo at Ribeirao Preto (March, 2010 – January, 2011). Whereas M. quadrifasciata naturally occurs in the study region (Brazilian Southeast), M. subnitida is restricted to the Brazilian Northeast. This difference in geographic distribution and concordant climatic specializations suggest differences concerning the environmental window between the two species. We investigated potential differences between the species concerning the thermal window within which foraging occurs, and consequent differences in foraging activity, visited pollen sources, and colony survival. The lower temperature limit for M. subnitida (17 oC) was 5 °C above the lower temperature limit found in M. quadrifasciata (12 °C). This difference resulted in a considerable time lag concerning the onset of foraging between the bee species (maximum: 120 minutes), mainly so in the cold/dry season. Due to this delay in foraging, M. subnitida could benefit from highly profitable pollen sources (mass-flowering trees) that were in bloom during this time of the year. Possibly in consequence of this deficit in pollen intake, three of the six monitored colonies of M. subnitida did not survive the study period.