O papel do fenótipo e do ambiente sobre a diversidade e composição do nicho polínico de abelhas sem ferrão (Apidae: Meliponini) da Amazônia

Abstract

Niche breadth is a fundamental ecological trait, underlying major macroecological patterns as well as species responses to environmental change. Yet, the drivers of variation in niche breadth across geographic extents are poorly understood. Moreover, the extent to which climate change has affected niche breadth is uncertain. Plant-pollinator systems provide an opportunity to address these questions, given the wide variation in the degree of ecological specialization between and within species. Stingless bees (Meliponini) dominate pollinator assemblages in the Neotropics, and thus play key roles in ecosystem functioning and ecosystem service provision. In Amazonia, pollen gathering by stingless bee colonies has been assessed since the late 1970s over a vast geographic area. Here, we synthesized such studies to investigate the effects of phenotypic (body size), environmental (tree diversity and composition, rainfall), and anthropogenic factors (urbanization, climate change) on the realized pollen niche of stingless bee colonies. We compiled pollen data for 89 colonies of 36 stingless bees species, distributed across 48 sites over 1400 km of the Amazon Basin. Generalized Least Squares models (GLS) incorporating phylogenetic autocorrelation were used to test for responses of pollen taxonomic diversity (a measure of niche breadth) and pollen taxonomic composition (a measure related to niche overlap). After accounting for methodological differences among studies, we found that geographic variation in realized pollen niche was mainly related to urbanization and body mass. On average, urban colonies collected five times more pollen types than wild ones, and of different composition. In parallel, pollen diversity tended to decrease with body size, while bees with different sizes collected different pollen compositions. Furthermore, we found that, since the 1970s, pollen diversity used by colonies has decreased, while pollen composition has changed, possibly due to phenological mismatch with and/or shifts in species composition of flower resources. Overall, our results suggest that the realized pollen niche of Amazonian stingless bees has been significantly restricted by direct (urbanization) and indirect human impacts (climate change) during the Anthropocene.