Land-use history drives contemporary pollinator community similarity

Habitat loss, especially within agriculture, can be a threat to biodiversity. However, biodiversity may respond slowly to habitat loss, taking time to undergo successional change following a disturbance. Despite the fact that historic processes often mediate current patterns of biodiversity, most studies focus only on contemporary factors. Our research examines how both contemporary and historic environmental factors impact current pollinator community similarity, or beta-diversity. We examine two hypotheses: H1) contemporary land-use predicts community similarity, but also that land-use history has long-lasting effects on beta-diversity; H2) the specific response to contemporary and historic environmental factors is explained by variation in pollinator species life-history traits. We sampled 36 pollinator communities over a three-year period across cotton fields varying in historic and contemporary land-use. Using multiple regression on distance matrices (MRDM), we investigate correlations between community similarity and differences in contemporary and historic environmental factors. First, we show that increased time between sampling events and the loss of semi-natural habitat over a 19-year period led to decreased community similarity. Interestingly, neither geographic distance nor contemporary environmental factors contributed to similarity. Second, we show that much of the variation in community similarity is due to variation in pollinator species life-history traits, such as foraging ability and diet breadth. Results indicate that land-use history has long-lasting effects on community composition, greater than effects exhibited by contemporary factors. These legacy effects are critical considerations for conservation as their omission may lead to overly optimistic assessments of biodiversity in recently disturbed habitats.