Meeting Abstract
Body mass influences various morphological, behavioral and physiological traits, but effects on immune systems have been little studied. By contrast, life-history characteristics of species and individuals has been found to influence various aspects of immunity, but many of these effects may manifest because effects of body mass on life history traits themselves. To discern the forces that shape immunity among species and hence understand broadly what factors mediate variation in immune systems, we examined how leukocyte counts relate to body mass and various life-history traits in 400 species of mammals spanning 5 orders of magnitude in mass. Total white blood cell (WBC), neutrophil and lymphocyte counts were compiled from the International Species Information System (ISIS), and life-history traits and body mass were extracted from Pantheria. We first determined whether body mass or various life-history traits (e.g. longevity, reproductive pace-of-life) better predicted immune system composition; a second model was then generated to reveal how different leukocyte types scaled with body mass. We found that total WBCs scaled positively to body mass across species and this effect was strongly driven by neutrophils. Lymphocytes however scaled negatively to body mass among species. These relationships indicate that the size of hosts alone influences how species cope with infections, which could partly explain why some host species pose greater risk than others to community-level disease dynamics.
