Reproductive And Immune System Interactions In The Context Of Life History And Sexual Selection Theory

Host variation in parasite load abounds, both within and across natural populations. The forces that shape and maintain this variation, however, are much less obvious. Over the past two decades, the emerging field of ecoimmunology has begun to address the underlying sources of this variation and its evolutionary consequences. Clearly, spatial and temporal heterogeneity in the environment contribute to variation in host parasite load by varying parasite distribution and abundance. However, host variation in the ability to acquire resources, and differences in how these resources are allocated, also play an integral role in parasite susceptibility. That is to say, not all individuals within a population are capable of managing the cost of immune defense, or may employ different cost-managing strategies. This realization has spurred a surge in studies focused on how immune pathways compete with other costly physiological pathways, such as those associated with reproduction. Interest in this relationship has no doubt been driven by the reproductive system\u27s high energetic cost and its direct association with host fitness. In this chapter, I examine the interactions between reproduction and immunity to highlight the simultaneous role both play in the evolution of immunological and reproductive adaptations. I begin by placing this interaction in the context of life history theory and discuss how competition for limited resources may constrain the evolution and expression of both systems. I then discuss the role that parasites play in directly shaping reproductive adaptations through sexual selection. In this discussion, I attempt to shed light on the lingering controversy that has overshadowed genetic benefit models and provide concrete predictions for future directions