Ecoimmunology at spatial scales.

IN FOCUS: Becker, D. J., Albery, G. F., Kessler, M. K., Lunn, T. J., Falvo, C. A., Czirják, G. Á., Martin, L. B., & Plowright, R. K. (2020). Macroimmunology: The drivers and consequences of spatial patterns in wildlife immune defence. Journal of Animal Ecology, 89, 972-995. Ecoimmunology seeks to identify and explain natural variation in immune function. Most research so far has focused on differences among individuals within populations, which are often driven by trade-offs in resource allocation between energetically costly immunity and competing processes such as reproduction. In their review article, Becker et al. (2020) have proposed a framework to explicitly address habitat- and population-level differences in wildlife immune phenotypes. Termed macroimmunology, this concept integrates principles from ecoimmunology and macroecology. Becker et al. (2020) have highlighted three non-mutually exclusive habitat features that are likely to vary at spatial scales and influence immune function: (a) parasite pressure, (b) abiotic and biotic factors and (c) anthropogenic changes. However, a large and robust body of literature suitable for synthesis to detect macroimmunology patterns and effect sizes is not yet available. Through their systematic review and critical assessment, Becker et al. (2020) identified common problems in existing research that hinders spatial inferences, such as a need for spatial replication in study design and statistical analyses that account for spatial dependence. Overall, macroimmunology has the potential to identify and even predict spatial patterns in immune phenotypes that form the mechanistic underpinnings of important wildlife disease processes, and this review represents an important step to realizing these goals.

Spatial Variation in the Inflammatory Response of House Sparrows in their Native Range.

Characterizing spatial differences in wildlife immunity is the first step to identify environmental drivers of host defense and disease risks. The house sparrow (Passer domesticus) is a model system for ecoimmunology, but spatial differences in immunity have been largely restricted to the invasive range of this global species. We provide an initial test of spatial variation in immune response to phytohemagglutinin in the native range, finding that birds from Romania have greater inflammatory responses than birds from Egypt. Future broad surveys across the house sparrow native range could contextualize these differences and determine underlying drivers.