78.6 Friday, Jan. 6 Island life and innate immunity: combining comparative and experimental approaches to better understand avian immune system evolution MATSON, K.D.*; MAUCK, R.A.; LYNN, S.E.; TIELEMAN, B.I.; University of Groningen; Kenyon College; The College of Wooster; University of Groningen firstname.lastname@example.org
Continents and isolated islands may present their avian residents with different disease-related selection pressures. Thus, these birds and their immune systems may follow different evolutionary trajectories. We compared continental and insular populations of Eastern bluebirds (Sialia sialis) to investigate how island life shapes immune function and, in turn, how immune function relates to growth and development. To do this, we integrated an experimental manipulation into the comparative framework. Instead of using an immune challenge, which is typically intended to induce responses and force tradeoffs among limited resources, we attempted an immune enhancement: chicks were supplemented with lysozyme throughout the nestling period. Lysozyme, an anti-inflammatory and anti-bacterial protein found in eggs and plasma, attacks cell-wall peptidoglycan and lyses bacteria. We hypothesized lysozyme supplementation would increase immune defense without increasing production costs. We predicted this treatment would minimize the adverse effects on growth of the low-grade and systemic inflammation caused by the antigenic milieu. Differences between locations in terms of treatment effects (i.e. a significant treatment by location interaction) would provide evidence for population-specific disease-related selection pressures. We collected and analyzed plasma samples, we recorded body and feather growth measurements, and we quantified chick feeding rates. Our preliminary results suggest that continental and insular bluebird populations differ and that lysozyme supplementation affects chick growth, but we found little evidence of treatment by location interactions.