Dietary differences between grasshoppers are associated with life history tradeoffs in an alpine meadow

Abstract

AbstractDietary differences are often observed among generalist herbivores co‐occurring in the same community. However, the factors underlying the differences remain poorly understood. In the context of insect herbivores, we hypothesized that interspecific dietary differences are associated with life history traits. Specifically, we hypothesized that the size of wings as well as gender participate in defining dietary preferences, that is, long‐winged species and males will tend to forage on plants with high C/N to maximize dispersal and mating, whereas short‐winged species and females will forage on N‐rich plants to maximize egg production. We tested this hypothesis by examining the diets of the males and females of three long‐winged and two short‐winged grasshopper species in an alpine meadow. The dietary composition and relative abundance of each species were determined using DNA meta‐barcoding. The data showed that the consumed plant species were similar among all of the grasshopper species and between the males and females. However, quantitative differences in the diets were significant between the long‐winged and short‐winged guilds and between the males and females of each species. Consistent with the hypothesis, (1) the long‐winged species fed more on monocots with high C/N, whereas the short‐winged species fed more on legumes with high N contents, (2) for each short‐winged species the males fed more on monocots with high C/N compared to the females, and (3) across all grasshopper species, egg numbers were positively associated with the weighted dietary N. These data indicate that the dietary preferences of these generalist grasshoppers are associated with life history tradeoffs.