Date of Award

Spring 1-1-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Museum and Field Studies

First Advisor

Cesar R. Nufio

Second Advisor

Dena M. Smith

Third Advisor

Robert P. Guralnick

Abstract

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. Along elevational gradients converse Bergmann clines, a decrease in body size with an increase in elevation, are commonly observed within insects when seasonality is present. No cline may also be observed when insects compensate for an abbreviated season by increasing their growth rate at high elevations or when environmental conditions fail to produce an effect. However, a key trait that has not been previously considered to influence the observed size cline of an insect is dispersal potential. Here, I hypothesize that an increase in dispersal potential, which suggests an increase in gene flow, impacts the type of size cline exhibited by grasshoppers across an elevation gradient. The impact of dispersal potential on two key life history traits associated with body size, reproductive potential and reproductive output, is also examined. I use two long winged species, Melanoplus sanguinipes and Camnula pellucida, to represent the high dispersal group and two short winged species, Aeropedellus clavatus, and Melanoplus boulderensis, to represent the low dispersal group. My findings support the hypothesis that dispersal potential influences the body size-elevation relationship and reproductive potential of a grasshopper species across an elevation gradient. However, my findings fail to show dispersal potential impacts reproductive output. This study suggests dispersal potential may influence the evolution of body size of insect species and should be considered in future studies.

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