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Most organisms are resource limited. Such limitations can result in tradeoffs between life history traits -- any traits that affect survival or reproduction. Flight polyphenic field crickets are thought to be a classic example of such a life history tradeoff, in which individuals tradeoff investment in flight capability and investment in reproduction. This polyphenism results from the interaction of two morphological traits: wing morphology (short or long) and flight muscle morphology (functional pink or non-functional white), and is affected by both genes and the environment. I examined life history traits of a flight polyphenic field cricket, Gryllus lineaticeps. First, I investigated whether females and males of flight capable and flightless morphs express alternative reproductive tactics congruent with their alternative life histories. I hypothesized that individuals in poor environments invest in flight capability, making it easier to locate mates, at the cost of early reproduction, while individuals in good environments invest in early reproduction, at the cost of flight capability. My results supported these hypotheses in both females and males. Next, I investigated costs, benefits, and constraints on the environment specific expression of life history traits. Having found that individuals with developed flight muscles pay a reproductive cost, I asked whether they gain flight capability. I found that only individuals with both long wings and developed flight muscles can fly. In addition, I found that flight muscle development and breakdown have correlated effects on other traits such as jumping ability, a trait used to escape predators and therefore likely to have survival consequences, leading to the conclusion that, how resources are allocated between flight capability and reproduction may be constrained from tracking environmental shifts due to selection for/against correlated traits. Lastly, I examined this life history tradeoff in the field. I found that different morphs of field caught individuals tradeoff flight capability and reproduction, by varying investment in reproductive tissues and lipids used for energy storage and egg production. This series of experiments provides a comprehensive look at life history evolution in a phenotypically plastic species.
Advisers: William E. Wagner Jr. and Anthony J. Zera