Host specialization in plant-galling interactions: Contrasting mites and insects

Abstract

Galling arthropods represent one of the most specialized herbivore groups. On an evolutionary scale, different taxa of insects and mites have convergently adapted to a galling lifestyle. In this study, we have used a multi-taxonomic approach to analyze the interaction specialization between gall-inducing mites and insects and their host plants in the Nitra City Park (Nitra, Slovakia). We used four ecological descriptors for describe plant-galling interactions: number of host plant species used by each arthropod species, galling specificity on host plant species (specificity), exclusivity of interactions between galling and plant species (specialization) and overlap of the interactions between arthropod species (similarity). We have found 121 species of gall-inducing arthropods, totaling 90 insects and 31 mites occurring on 65 host plant species. Our results reveal that mites have high specialization and low similarity of interactions in comparison to insects. A multiple-taxonomic comparison showed that these differences are triggered by gall-wasps (Hymenoptera: Cynipidae), the taxon with the lowest levels of specificity of plant-galling interactions (i.e., occurring on different host plant species). Our findings are indicative of different patterns of interaction between distinct gall-inducing arthropods taxa and their host plants, despite the ecological convergence of different taxa to a highly specialized herbivorous habitat.