Climate mediates roles of pollinator species in plant-pollinator networks

Aim: Understanding how climate conditions influence plant-pollinator interactions at the global scale is crucial to understand how pollinator communities and ecosystem function respond to environmental change. Here, we investigate whether climate drives differences in network roles of the main insect pollinator orders: Diptera, Coleoptera, Lepidoptera and Hymenoptera.Location: Global.Time period: 1968-2020.Major taxa studied: Diptera, Coleoptera, Lepidoptera and Hymenoptera.Methods: We collated plant-pollinator networks from 26 countries and territories across the five main Koppen-Geiger climate zones. In total, we compiled data from 101 networks that included > 1500 plant species from 167 families and > 2800 pollinator species from 163 families. We assessed differences in the composition of plant-pollinator interactions among climate zones using a permutational ANOVA. We calculated standard network metrics for pollinator taxonomic groups and used Bayesian generalized mixed models to test whether climate zone influenced the proportion of pollinator network links and the level of pollinator generalism.Results: We found that climate is a strong driver of compositional dissimilarities between plant-pollinator interactions. Relative to other taxa, bees and flies made up the greatest proportion of network links across climate zones. When network size was accounted for, bees were the most generalist pollinator group in the tropics, whereas non-bee Hymenoptera were the most generalist in arid zones, and syrphid flies were the most generalist in polar networks.Main conclusions: We provide empirical evidence at the global scale that climate strongly influences the roles of different pollinator taxa within networks. Importantly, non-bee taxa, particularly flies, play central network roles across most climate zones, despite often being overlooked in pollination research and conservation. Our results identify the need for greater understanding of how global environmental change affects plant-pollinator interactions.