Assistant professor University of Florida Gainesville, Florida, United States
Abstract: A classic question in ecology concerns how species in diverse communities partition resources to coexist. Trait matching, which involves identifying traits that mediate linkages between trophic levels, is a potentially useful method for revealing the mechanisms by which consumer species partition resources. Herbivore species may require a specific assortment of functional traits to consume certain plant species based on their functional traits (i.e., trait matching). The goal of our research was to experimentally test the matching of a variety of plant and insect herbivore traits to understand the mechanisms that govern community assembly. We hypothesized 1) that grasshopper feeding mechanics (i.e., incisor strength) would be positively correlated with leaf toughness, and 2) that body size would be positively correlated with leaf nitrogen content. We tested these hypotheses by performing cafeteria style assays in experimental mesocosms. Each mesocosm consisted of a mesh butterfly cage with cuttings of 16 plant species. The plant species used in this experiment represented 8 families and were classified as grasses, forbs, legumes, and woody vegetation. Eleven grasshopper species were tested, representing three functional groups: grass-feeders, forb-feeders, and mixed-feeders. A variety of plant and insect functional traits were measured on all species used in this experiment. Individual grasshoppers were placed in the mesocosms and allowed to feed for 48 hours. At the end of the assay, plant damage was assessed and the feeding preferences of each grasshopper species was determined. We found that grasshopper incisor strength was correlated with leaf dry matter content, suggesting that strong incisors are required to consume plant species with tough, recalcitrant leaves. Additionally, we found that grasshopper body size was were correlated with leaf nitrogen content, suggesting larger bodies grasshopper species preferentially consume nutritious plant species likely to meet their high metabolic demands. Our results highlight that grasshopper communities partition their feeding niches based on functional trait matching between grasshopper and plant species. Understanding these linkages may ultimately be useful for predicting how plant and insect herbivore communities are assembled under field conditions.
