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ABSTRACT Historically, the fields of ecoimmunology, psychoneuroimmunology and disease ecology have taken complementary yet disparate theoretical and experimental approaches, despite sharing critical common themes. Researchers in these areas have largely worked independently of one another to understand mechanistic immunological responses, organismal level immune performance, behavioral changes, and host and parasite/disease population dynamics, with few bridges across disciplines. Although efforts to strengthen and expand these bridges have been called for (and occasionally heeded) over the last decade, more integrative studies are only now beginning to emerge, with critical gaps remaining. Here, we briefly discuss the origins of these key fields, and their current state of integration, while highlighting several critical directions that we suggest will strengthen their connections into the future. Specifically, we highlight three key research areas that provide collaborative opportunities for integrative investigation across multiple levels of biological organization, from mechanisms to ecosystems: (1) parental effects of immunity, (2) microbiome and immune function and (3) sickness behaviors. By building new bridges among these fields, and strengthening existing ones, a truly integrative approach to understanding the role of host immunity on individual and community fitness is within our grasp. 

Abstract To promote survival and fitness, organisms use a suite of physiological systems to respond to both predictable and unpredictable changes in the environment. These physiological responses are also influenced by changes in life history state. The continued activation of physiological systems stemming from persistent environmental perturbations enable animals to cope with these challenges but may over time lead to significant effects on the health of wildlife. In the present study, we tested how varying environmental perturbations driven by tourism and associated supplemental feeding affects the energetics, corticosterone and immunity of six discrete populations of the northern Bahamian rock iguana (Cyclura cychlura inornata and Cyclura cychlura figginsi). We studied populations within and outside the reproductive season and quantified tourist numbers during sample collection. Specifically, we measured clutch size, body condition, plasma energy metabolites, reactive oxygen species, baseline corticosterone concentrations and immune function of male and female iguanas from each population to address whether (i) disparate physiologies are emerging across a gradient of tourism and feeding, (ii) both subspecies respond similarly and (iii) responses vary with season/reproductive condition. We found significant effects of tourism level, season and their interaction on the physiology of both C. c. inornata and C. c. figginsi, supporting the idea that tourism is leading to the divergence of phenotypes. Specifically, we found elevated plasma energy metabolites, oxidative stress and a measure of innate immunity (bactericidal ability), but reduced corticosterone concentrations with increasing tourism in both subspecies of rock iguanas. These physiological metrics differ according to the level of tourism in both subspecies and persist across seasons despite variation with natural seasonal and reproductive changes. These findings suggest that anthropogenic disturbance results in disparate physiologies in northern Bahamian rock iguanas.