236 Figure 6.30 A conceptual framework for ecological immunology. An overview of ecological inputs that influence a host organism and the nature of the organism's defense or immune responses. The nature of defense and immune responses can be expected to be greatly influenced by the ecological context in which an organism occurs. This approach provides a framework to better understand the responses of organisms to their environments and provides a compelling way to think about the evolution of immune responses. Host reproductive effort and elaboration of sexual ornaments exampl in host behavior When we understand something standpoint, some manipulations might best play to the senses of their pre- ite's daceous hosts. Given how notoriously unresponsive we are as compared to other animals with respect to smell or hearing, it seems there is much yet to the predator relevant to its needs. Clearly, this field will continue to attract learn by considering parasite-mediated cues (such as odor) that might attract the attention of parasitologists and the popular press alike, the latter always on the lookout for more jaw-dropping stories of real-life zombies. 6.7 ECOLOGICAL IMMUNOLOGY new, new, fast-paced Ecological immunology, or ecoimmunology, is a relatively field that has at its core the idea that both biotic and abiotic features of the environment influence the evolution and function of immune responses and that the nature and extent of immune responses help us better under- stand an organism's ecology. Figure 6.30 presents a conceptual framework for ecological immunology, a framework that emphasizes the value of a cross-disciplinary approach. The ideas on which ecological immunology are based permeate this book. Chapter 4 provides examples for how symbi- onts influence host defenses and Chapter 5 highlights that vigorous immune responses are often a double-edged sword that can result in pathology. The concept of trade-offs-for example, the notion that a strong immune response might divert energy from reproduction-is discussed in Chapters 5 and 7. Also emphasized earlier in this chapter is that hosts may deploy a variety of defenses against parasites, not always of an immunological nature. Chapter 7 also discusses the importance of parasite population genetics, con- cepts of parasite-host coevolution and the intersection of immunology with sexual ornamentation to affect mate choice, all part of the canon of ecological immunology. In this section, we touch on a few additional ideas that further flesh out the meaning of ecological immunology. To provide just a few examples of the ecological inputs indicated in Figure 6.30, consider that the effectiveness of immune responses of hosts such Ecological Factors Diet quality and abundance Prior history of parasite exposure Presence of co-infections Nature/density size/connectivity of host population Environmental quality and Parasite effects on stress host behavior The Individual Host afford of trad success pelago in lim cumci antibo active respo fema ity of (Figu prod the 1 abili For unli ing red bee up- no res inf (el ta th is in t Behavioral avoidance of infection/self- medication Tolerance response vs. resistance response Deployment of innate or adaptive immune response, or both Symbiont- mediated defenses Exercising trade-offs between immunity and reproduction Social immunity Defense against parasite manipulations Nature of Defense and Immune Responses