Insects are ectothermic organisms that have physiological, behavioral and life-history traits directly influenced by their environment. Investigations have shown that many insects use melanin to permanently darken their cuticles in cooler or drier climates to improve thermoregulation and desiccation resistance. Melanin is a major component of pathogen defense in insects. This suggests that environmentally driven adaptive changes in cuticular melanin may non-adaptively shape insect immune function. This hypothesis has been referred to as climate-related Cuticle Dependent Immune Investment (climate-related CDII). Climate-related CDII also suggests that a warming climate could lead to the evolution of a weakened melanin-based immune response due to direct selection for lighter cuticles. Climate-related CDII has not been investigated with regard to climate change. Using Drosophila melanogaster, the first part of this study investigated if the documented pattern of lowered immune function in warmer temperatures offsets the expected gain in metabolic rate. The second part of this project investigated how a warming thermal environment will affect the evolution of insect immune function by quantifying changes in melanization and immune function over multiple generations in a changing thermal environment. In the first investigation there was evidence for weakened immune function in males, while females saw an offset by gaining a metabolic boost. The second investigation showed evidence that warming treatments evolved lowered overall immune function. This project gives evidence that insect immune function has the potential to be weakened by increasing temperatures. Insect immune function is a major contributing factor to insect abundances. A decrease in beneficial insects or an increase in harmful insects or pathogens they vector could have detrimental environment and human health consequences.
Master of Science (M.S.)
College of Sciences
Length of Campus-only Access
Masters Thesis (Open Access)
Perry, Danae, "Climate Change and the Evolution of Insect Immune Function" (2017). Electronic Theses and Dissertations. 5355.