Seasonal dynamics of plant-pollinator communities and their response to climate change

Background/Question/Methods

Despite evidence that climate warming shifts plant and pollinator phenologies, a general assessment of these shifts and their consequences on species assemblages is still lacking, especially for pollinators. In addition, phenological traits have been rarely considered in models of plant-pollinator networks, which has hampered exploring the consequences of climate warming and associated phenological shifts on the seasonal structure and dynamics of plant-pollinator networks. To increase our understanding of the consequences of phenological shifts on the dynamics of plant-pollinator networks, we analyzed phenological shifts of over 2,000 species of flower visitors by compiling a large database of occurrence data of flower visitor species across Europe. In parallel we developed a model of plant-pollinator networks explicitly structured by phenological and morphological traits, both types of traits being key determinants of the structure of mutualistic networks.

Results/Conclusions

Our results show that, on average, the mean flight date of European pollinators shifted to be 6 d earlier over the last 60 yr, while their flight period length decreased by 2 d. However, there is also substantial heterogeneity among species responses and our analysis further reveals that these shifts have overall decreased the overlap among pollinators’ phenologies within European assemblages, except in the most northeastern part of Europe. The analysis of the model shows that networks structured by phenology favour facilitation over competition within guilds of pollinators and plants, thereby increasing network persistence. These results indicate that beyond trophic mismatch, phenological shifts such as those induced by climate change can affect indirect effects within mutualistic assemblages, with consequences for biodiversity.