Masters Theses

Anne Grinnan

Date of Award

8-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

Christine Boake

Abstract

Temperature has been demonstrated to induce phenotypic plasticity in numerous insects for numerous traits. An organism of a specific genotype is said to exhibit phenotypic plasticity if it shows variation in a trait or traits that is dependant on changes in the external environment. A reaction norm is the function that relates the environments to which a particular genotype is exposed and the phenotypes that can be produced by that genotype. Genotype-by-environment interactions measure how genotypes vary in their· reaction norms. Trait responses to temperature can be examined with analyses that test for G by E interactions and display norms of reaction; thus telling us if different genotypes behave differently in different temperature environments. In the genus Nasonia, females produce large numbers of virtually identical offspring in a single clutch, making them ideal for a study of reaction norms. Nasonia vitripennis, N. giraulti and N. /ongicomis are parasitic wasps that parasitize various species of blow flies. I tested two strains of each of the three species for differences in emergence time, proportion of males and tendency to diapause due to different temperature environments. I also tested for genetic differences among the strains and any G by E interactions that might occur. I found that emergence time was the same for all species and all strains tested; as temperature increased the emergence time decreased. The proportion of males per clutch tended to have less of a plastic response, but there is evidence of a genetic response, with strains of the same species behaving differently. Diapause showed more genetic than temperature variation. In general, the G by E responses were modest.

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