Demographic trade-offs decouple pollination services from plant population growth

Abstract

Abstract Most plants require animal pollination to reproduce, prompting concern that pollinator declines immediately threaten plant populations. This concern is warranted if pollinator-mediated seed losses cause declines in plant population growth rates (λ). However, demographic trade-offs might reduce the risk of population decline if seed loss improves performance elsewhere in the life cycle. We conducted a multi-year pollination manipulation on four species and measured how demographic vital rates and λ responded. Seed responses did not predict net changes in λ. Reduced pollination decreased seed production, but only caused a net decrease in λ in one species; in the others, improved survival buffered λ. Increased pollination boosted seed production, but at a cost to survival that caused a net reduction in λ in three species. Our results highlight the importance of demographic trade-offs for understanding the impacts of pollinator declines on plant biodiversity and, more broadly, the population-level impacts of changing mutualisms.