Physiological and evolutionary consequences to Drosophila melanogaster of immune response to parasitism by the wasp Asobara tabida.

摘要

Parasites are ubiquitous and can exert a wide range of negative effects on their hosts. Clearly, hosts that can resist parasitism should have a selective advantage over conspecifics that cannot. Yet, host populations remain susceptible to some parasites. Could genetic heterogeneity in the host's ability to resist parasites reflect costs of maintaining and/or mounting the immune response?;Costs of mounting an immune defense can arise from two types of causes: (1) evolving and maintaining the machinery necessary to mount the response, (2) and actually running this machinery in response to an attack. At first consideration, evolving resistance and launching the immune response appear adaptive against the threat of parasitism (the alternative being death or severe debilitation). However, the immune response, as any other trait, must compete for limited resources. Consequently, energy that is used in mounting the immune response must be withdrawn from other functions important to fitness.;In this collection of studies, I addressed the question, "What is the impact on fitness of mounting an immune defense against parasitism?" First, I addressed the costs of launching an immune response against actual attack. Because flies are attacked by this parasitoid early in its life cycle, I measured costs of mounting an immune response at two different life stages. Second, I studied the effect of exposure to parasitoids in the absence of an actual attack. Third, I studied the impact of parasitism on ability to survive abiotic stress. Fourth, I studied the responses of different genotypes (isogenic lines) to parasitism.