Guilds and functional traits as drivers of trophic specialization in tropical herbivores

Abstract

Host-plants are the key niche dimension for herbivore insects. Guilds of herbivores feed on different plant parts and acquire resources in varying ways. Herbivore and plant traits, as well as guild membership, may influence the specialization of herbivores. We will use a new phylogenetically controlled specialization metric to address the following questions in two papers: 1) How specialized are different herbivore guilds? 2) What is the structure of variation in specialization for guilds sharing the same host-plant? 3) Do herbivore functional traits, such as body size, feeding mode, mobility, interaction intimacy with plants, among others, affect the level of specialization? 4) Do plant traits, such as nutrient content, amount and type of defenses, among others, influence the specialization of the herbivore fauna feeding on it? We address questions 1) and 2), using an extensive database of plant-herbivore interactions from Papua New-Guinea produced by the group led by Prof. V. Novotny, in which we verify marked differences in specialization among guilds, as expected; these differences hold even when comparing species from the same order that belong to different guilds. For a subset of plants that were sampled for most guilds, variation in specialization within guilds among host-plants is much lower than expected, while variation between guilds within plants is marginally higher than expected. This project will be completed and prepared for publication during the present fellowship. A second study will be developed to address questions 3) and 4), based on the same interaction database, and using trait databases for plants and herbivores, as well as phylogenetic and taxonomic data to make controlled comparisons among species. (AU)