Abstract
Agriculture driven landscape changes has caused worldwide forest loss and fragmentation, seriously affecting biodiversity and ecosystem services, amongst which pollination is remarkably important. Bees are an essential pollinator group for forest plant populations and food production in tropical landscapes. They are also dependent on forested environments which are essential to maintain their diversity and pollination services. We analyzed bee diversity in contrasting forest and adjacent non-forest patches to evaluate if bees can use complementary non-native environments in heterogeneous altered tropical landscapes. The effect of landscape level heterogeneity and forest amount on bee diversity was also assessed. Our hypothesis was that bee communities would be more rich and diverse inside the forest understory, but due to supplementary foraging behaviors they would be more abundant in non-forested areas where flower availability is higher. We actively sampled bees visiting flowers within forest patches and in surrounding non-forest open areas between the Cantareira and Mantiqueira mountain ranges in São Paulo, Brazil. We found higher bee richness and diversity in open areas than in forest patches, partially denying our initial hypothesis but supporting that bees are more abundant in non-forest areas. We found strong indication that landscapes with higher amount of forest and environmental heterogeneity can provide more resources for bees through resource complementation processes, maintaining their diversity in the landscape. The presence of forest patches close to crop and open areas is of utmost importance for the conservation of bees and pollination services with important consequences for land management in tropical environments.
Highlights
Over the years, human activity has modified about 43% of Earth’s land surface (Barnosky et al, 2012) by converting natural areas for several human activities, among them agriculture and urbanization (Lambin et al, 2001)
Our objective was to assess the influence of forest cover and landscape heterogeneity on the abundance and diversity of bees foraging within the forest and in adjacent open areas, which can be used as complimentary habitat in the face of forest loss
We found the opposite response for bee diversity and richness inside the forest, with a negative effect of forest amount on these variables, which was more intense for bee diversity (Fig 3 a, b)
Summary
Human activity has modified about 43% of Earth’s land surface (Barnosky et al, 2012) by converting natural areas for several human activities, among them agriculture and urbanization (Lambin et al, 2001). Habitat loss and fragmentation can increase the isolation of individuals and populations, affecting dispersion and foraging capacity (Brosi et al, 2008; Ferreira et al, 2015; Boscolo et al, 2017). This isolation compromises bees’ chances to find mating partners, food, and nesting resources, with negative effects on population sizes and genetic diversity. Habitat loss and fragmentation are being recognized as one of the top determinant factors for the general worldwide decline of bee populations detected during the last few years (Potts et al, 2016)
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