Interspecific and intraspecific variation in grasshopper (Orthoptera: Acrididea) molar form: implications for dietary ecology.

Abstract

Like many mammals, grasshoppers (infraorder Acrididea) chew using molariform structures. Despite decades of research on mammals, little is known about grasshopper molar form and how it relates to grasshopper feeding biomechanics, diet, dietary ecology and evolution. Here, we develop a method for quantifying molar form and apply it to two species of distantly related grasshoppers with different diets (Phymateus saxosus, seven females; Valanga nigricornis, seven females, 11 males). We show that there are quantifiable differences in molar form, potentially related to diet. There are some differences in molar shape between left and right molars in both species and sexes, and significant differences in molar size, potentially due to scaling. Like in mammals, molar wear can cause large differences in molar shape. Species differences in molar shape did not match what was expected based on mammalian molar functional morphology. Dental topographic analysis is a promising new avenue for quantifying molar form in grasshoppers and a distinct advantage over traditional two-dimensional microscopy methods, and promises to reveal much about the biology, biomechanics and evolution of Acrididea.