Climate warming changes synchrony of plants and pollinators in Germany

Abstract

Climate warming changes the timing of many life-history events across the biosphere. When interacting organisms, such as plants and their pollinators, experience these changes differently, climate change may disrupt their interactions and ultimately affect the structure and stability of associated communities and ecosystems. However, so far there is little empirical data on the strength and consistency of such phenological mismatches. We used occurrence records from the Global Biodiversity Information Facility (GBIF) to examine trends in the phenologies of 1,274 plants and 88 associated insect pollinators (butterflies/moths, flies, bees, and beetles) in Germany since the 1960s. We found strong and consistent phenological advances in plants (on average -4.5 days per decade), but differences in the extent of shifts among pollinator groups (-3.2 and +2.0 days per decade for butterflies and moths, and beetles, respectively). The observed temporal trends in plant and insect phenologies were generally associated with interannual temperature variation (plants: -7.6 days, butterflies and moths: -4.4 days, beetles: +1.4 days per +1°C), and thus likely driven by climate change. In plants, phenological advancement did not depend on their level of pollinator dependence. When examining the temporal co-occurrence of 1,797 plant-pollinator pairs over the decades from 1980 onwards, the temporal trends in their synchrony again strongly depended on the pollinator group: while the synchrony of plant-butterfly interactions remained unchanged during the last decades, interactions with bees and hoverflies tended to become more synchronized, mainly because the phenology of plants responded more strongly to climate change and plants caught up with these pollinators. Still, if the observed trends continue, then these interactions are expected to become more asynchronous again in the future. Our study demonstrates that climate change affects the phenologies of different interacting groups of organisms, and that this also influences their synchrony, with potential far-reaching ecological consequences.