No simple way to explain trophic structure in terrestrial palaeoecosystems using plant-insect interactions

Terrestrial ecosystems are defined by their plant and animal communities and how they interact and by abiotic factors. Insects are the main herbivores in forests and determine trophic structure, but what drives herbivore richness and frequency in temperate forests is not fully understood. Here we analyzed insect damage richness and frequency in 5,000 fossil leaves deposited during early Miocene at 20–17 Ma along a latitudinal gradient from Europe to Turkey in a temperate climate setting. We show that damage <i>frequency</i> is linked with abiotic factors (temperature, precipitation seasonality) while damage <i>richness</i> is linked with biotic factors (plant richness, biome). Univariate analysis of insect damage consistently suggested closer trophic similarity between the Mediterranean and either the one or the other Central European plant assemblage. In contrast, multivariate analysis indicated closer similarity between two Central European sites highlighting the importance of biogeographic legacy and geographic closeness to the plant-insect interaction patterns.