Patterns of pollinator community disassembly resulting from forest fragmentation

Pollinator species richness generally decreases with increasing human land use intensity. The order in which species are lost, however, is poorly understood, and could have important consequences for ecosystem functioning. We investigated patterns of native pollinator community disassembly across a forest fragmentation gradient in New Jersey, USA. Pollinators were collected at 20 sites for a total of >5000 specimens. First, to identify the species characteristic of undisturbed forest, we used NMDS ordination to contrast pollinator species composition between undisturbed and highly disturbed sites. This identified 38 target species used in subsequent analysis. Second, we evaluated several traits for each pollinator species, including abundance and the number of plant species visited. Lastly, we investigated the order of pollinator species loss with regard to these traits, using data from 13 sites that spanned a gradient of forest fragmentation; these sites were not used for either of the foregoing analyses. We compared the observed order of species loss to a null model based on random loss order using a Monte Carlo simulation. We found that rare pollinator species, and pollinator species with greater dietary specialization, were lost significantly (P<0.05) more quickly than were abundant species and dietary generalists. The results suggest that rarity and floral specialization are predictors of extinction risk for native forest pollinators, and for the plants that depend upon them.