Greater phylogenetic distance from native oaks predicts escape from insect leaf herbivores by non-native oak saplings

Abstract

Premise: Non-native plant species have been hypothesized to experience lower herbivory in novel environments as a function of their phylogenetic distance from native plant species. Although recent work has found support for this prediction, the plant traits responsible for such patterns have been largely overlooked.

Methods: In a common garden experiment in northwestern Spain, we tested whether oak species (Quercus spp.) not native to this region that are phylogenetically more distantly related to native species exhibit less insect leaf herbivory. In addition, we also investigated plant traits potentially correlated with any such effect of phylogenetic distance.

Results: As expected, phylogenetic distance from native species negatively predicted insect leaf herbivory on non-native oaks. In addition, we found that the leaf traits, namely phosphorus and condensed tannins, were significantly associated with herbivory, suggesting that they are associated with the effect of phylogenetic distance on leaf herbivory on non-native oak species.

Conclusions: This study contributes to a better understanding of how evolutionary relationships (relatedness) between native and non-native plant species determine the latter's success in novel environments via locally shared enemies, and encourages more work investigating the plant traits that mediate the effects of phylogenetic distance on enemy escape.

Keywords: Quercus; Fagaceae; enemy release; herbivory; nutrients; phenolic compounds; plant defense; temperate biome.