PARENT SESSION
Contributed Oral Session 168: Invertebrate Ecology: Food Webs, Physiology, and Communities
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal
Sex, body size, and the C:N:P stoichiometry of grassland insects.
Kay, Adam*,1, Haarstad, John2, Hobbie, Sarah2, Schade, John3, 1 Department of Biology, St. Paul, MN, USA2 Department of Ecology, Evolution and Behavior, St. Paul, MN, USA3 Department of Integrative Biology, Berkeley, CA, USA
ABSTRACT- Differences in carbon:nitrogen:phosphorus (C:N:P) stoichiometry among consumer taxa can reflect variation in phenotypes that determine the form of ecological interactions. Recent work has identified significant stoichiometric variation among terrestrial insects, suggesting that compositional differences among consumers may influence food web dynamics in terrestrial systems. This work has focused almost exclusively on interspecific variation in consumer stoichiometry because active regulation of nutritional state is thought to limit compositional change within animals. Here we describe substantial variation in C:N:P stoichiometry within grassland insect species, and show that much of it can be explained by differences in body mass and sex. In many species, we found that mean P concentration did not differ significantly among male and female adults. However, P often showed similar strong negative allometries in males and females, and females were generally larger than males. As a result, females in 25 of 36 species sampled contained significantly higher P concentrations than did same-sized males. These differences were substantial: in 19 species, females contained over 30% more P than males after accounting for allometry. Sex-specific allometric scaling of P differed significantly across taxa, suggesting the mechanism explaining the relationship between P and body size will depend in part on variable internal features or ecological constraints. Although N concentrations decreased and C concentrations increased with adult body mass in most species, we rarely found mass-specific differences in N or C concentrations between males and females. Elucidating the functional consequences of sex- and size-related differences in C:N:P stoichiometry should help to develop a more mechanistic, material-based understanding of sexual interactions and trophic dynamics in insects.
Key words: stoichiometry, allometry, sex, insect