Body size variation in a guild of carrion beetles

Abstract

Body size is a key biological trait, influencing the biomechanics, physiology, behaviour, and ecology of species. Describing variation in body size within and among co-occurring species within an ecological guild can provide important context for understanding the ecology of species and the structure of ecological communities. Here, we focus on a guild of carrion beetles (Coleoptera: Silphidae) co-occurring in southeastern Ontario, Canada. We examine how body size varies (i) among species, (ii) within species, including among sexes, and (iii) across the active season, contrasting estimates of size based on mass with those based on morphological structure (elytron length). We find that body size varies significantly both within and among species. Five focal species show evidence for sexual dimorphism in size. All focal species show significant seasonal variation in size, but these patterns differ across species, and depend on our estimates of size. Overall, the observed variation in body size is most consistent with widespread environmental constraints on size and (or) diverse selective pressures favouring different sizes within and among species. We discuss possible selective pressures acting on size within and among species; however, the causes and consequences of the variation in body size that we describe remain to be discovered.