Differential life history traits of long and short winged grasshoppers across an elevation gradient

Body size is an important life history trait that determines reproductive success of insects through its effects on their physiology, ecology, and behavior. Changes in body size may have both a genetic component when local conditions select for optimal body size and an environmental component when it is influenced by temperature, food availability, and other environmental factors. Within grasshoppers body size can differ across space with a tendency for larger individuals and species to be associated with warmer and long-season areas. Along elevation gradients, this body size pattern is reflected in the propensity of grasshoppers to follow a converse of Bergmann’s rule, with smaller individuals being associated with higher altitudes. In this study we explored relationships between body size and elevation in two long winged, Melanoplus sanguinipes and Camnulla pellucida, and two short winged, Aeropedellus clavatus and M. dodgei, species along a gradient in Northern Colorado to explore the effects of dispersal potential on body size and fitness of insects. Our preliminary findings show that long winged species do not significantly change their body size along the gradient and although the total number of ovarioles and egg size did not differ among populations, the total number of functional ovarioles declined. The short winged species, in turn, displayed a negative body size to elevation relationship, a reduction in the number of ovarioles (but not functional ovarioles), and an increase in egg mass with elevation. Our study suggests that dispersal potential may affect a species’ ability to evolve an optimal body size.