Chapter 20 - Evolutionary and ecological immunology

Abstract

Immune defenses vary widely across individuals and species. The field of evolutionary and ecological immunology (also recognized as ecoimmunology) seeks to uncover both the ultimate and proximate drivers of this variability. In this chapter, we review key research areas, techniques, and future directions in this field, with a specific focus on free-living birds, which serve as valuable models. Assays to assess immune function vary depending on the immunological pathways and parasites of interest as well as the ability to repeatedly sample free-living individuals. Several new field assays seek to measure innate immune responses. These include the inflammatory and acute-phase responses, which integrate physiological and behavioral changes following infection. Recent progress in avian immunogenetics suggests the links between major histocompatibility complex (MHC) or innate immune genes and ecological context of disease dynamics in several free-living bird species. Development of the immune system in free-living birds is still understudied, especially in altricial species that develop slowly in the nest. Maternal antibody transmission remains a critical area of study, as it can provide significant pathogen resistance benefits but may carry important costs to offspring immune ontogeny. Lastly, we discuss the important role of immune system costs, both in resources and immunopathology, in driving life history trade-offs and variation in sexually selected signals.