The response of pollen-transport networks to landscape-scale climate variation

Abstract

Climate variation can have profound effects on the composition and diversity of species as well as species physiology and behavior. Such effects may have ramifications on the network structure of interacting species within a community. Our aim was to understand how landscape-scale variation in temperature and wind exposure influenced plant–pollinator diversity, composition, and network structure. We constructed pollen-transport networks at six sites along a temperature gradient in west Greenland. Half of these sites were naturally sheltered from katabatic winds, while the other half were exposed. At each site, we measured temperature, wind speed, and the presence of flowering plants. We netted insects and identified the insects and the pollen carried on their bodies. Network structure was quantified using connectance, nestedness, and specialization, three metrics related to the robustness of networks to environmental variation. We tested how temperature and wind speed affected the diversity and composition of insects, pollen, and plants flowering in sites, and network structure. Temperature zone and wind exposure did not explain variation in the richness, evenness, or abundance of insects or pollen, or the richness of plants flowering in sites. However, the composition of pollen and plants flowering in sites varied across temperature zones and levels of wind exposure. Despite the observed changes in pollen and plant community composition, we found that network connectance, nestedness, and specialization were unresponsive to landscape-scale variation in temperature and wind exposure. High generalization and opportunism among Arctic plants and pollinators may contribute to this lack of response.