Plant-insect interactions patterns in three European paleoforests of the late-Neogene—early-Quaternary

Résumé En

Plants and insects are constantly interacting in complex ways through forestcommunities since hundreds of millions of years. Those interactions are oftenrelated to variations in the climate. Climate change, due to human activities, mayhave disturbed these relationships in modern ecosystems. Fossil leaf assemblagesare thus good opportunities to survey responses of plant–insect interactions toclimate variations over the time. The goal of this study is to discuss the possiblecauses of the differences of plant–insect interactions’ patterns in Europeanpaleoforests from the Neogene–Quaternary transition. This was accomplishedthrough three fossil leaf assemblages: Willershausen, Berga (both from the lateNeogene of Germany) and Bernasso (from the early Quaternary of France). InWillershausen it has been measured that half of the leaves presented insectinteractions, 35% of the fossil leaves were impacted by insects in Bernasso and only25% in Berga. The largest proportion of these interactions in Bernasso werecategorized as specialist (mainly due to galling) while in Willershausen and Bergathose ones were significantly more generalist. Contrary to previous studies, thisstudy did not support the hypothesis that the mean annual precipitation andtemperature were the main factors that impacted the different plant–insectinteractions’ patterns. However, for the first time, our results tend to support thatthe hydric seasonality and the mean temperature of the coolest months could bepotential factors influencing fossil plant–insect interactions.