High bee functional diversity buffers crop pollination services against Amazon deforestation

Abstract

Predicting outcomes of land use change on biodiversity and ecosystem services remains a key priority for ecologists, but may be particularly challenging in diverse tropical ecosystems. Trait-based approaches are a key tool to meet this challenge. Such approaches seek functional mechanisms underpinning species’ responses to environmental disturbance and contributions to ecosystem services. Here, we use a functional trait approach to study effects of land use change on stingless bee communities and on pollination services to açaí palm (Euterpe oleracea, Arecaceae) in the eastern Brazilian Amazon. We compared traits of stingless bees visiting açaí inflorescences across a land use intensity gradient (low to high forest cover) to determine: (1) the role of traits in bee species’ responses to deforestation; (2) how deforestation affects functional composition of bee communities; and (3) whether bee traits better explain variation in açaí fruit production than species diversity metrics. We found that bee species’ responses to deforestation were non-random and predicted by body size, with small-sized bees more susceptible to forest loss, and changes in functional diversity of bee communities were important for pollination services. However, not all changes in functional diversity were associated with forest loss. Together, these results suggest that: (1) large tracts of minimally disturbed tropical rainforest are vital for the conservation of diverse stingless bee communities; (2) efficient pollination is contingent on bee species not only having divergent trait values (functional dispersion), but also traits’ relative abundance in communities (functional evenness); and (3) high functional diversity in stingless bee communities buffers açaí pollination services to loss of sensitive species. Thus, conservation strategies must focus on protecting wider biodiversity, not just ecosystem services, to guarantee conservation of native eusocial bee taxa. Doing so will safeguard crop pollination services, the pollination of native plant communities, and the long-term resilience of Amazon forest ecosystems.