Dissertation Research: The Evolution of Disease Susceptibility

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Zuk9902305How do animals balance the need for defense against disease against other needs such as growth or reproduction? One possibility is that one such costly effort is achieved by a trade-off with another. To investigate the role of such trade-offs, this research tests whether mounting an anti-microbial immune response is energetically costly, whether these costs affect the ability of individuals to survive and reproduce, and lastly, whether this proposed trade-off has a genetic basis. This research is being carried out using the fruit fly Drosophila melanogaster, a model system for the study of genetics, life history, and insect immunity. By comparing immune responses and measuring costs of immunity in flies that have been bred in the laboratory for specific genetic traits, the evolution of disease resistance can be measured. Parasites and disease are ubiquitous in natural populations, and parasites can decrease both the survival and reproductive ability of their hosts. One might therefore expect evolution of strong defenses against pathogens, yet susceptibility to disease remains high in many different organisms. One solution to this problem is that resistance is costly and trades off with an animal's ability to survive and reproduce. This research will contribute to our understanding of the role that such trade-offs play in maintaining disease susceptibility.