Data from: Life-history and ecological variables as drivers of the evolution of avian innate immune defences

Animals rely on immune defences to counteract pathogens and parasites, but
investing in immune defences limits the use of shared resources for other
functions. Therefore, the strength of immune defences is hypothesised to
be shaped by life history or broader ecology. To better understand
ecological and evolutionary patterns in innate humoral immune defences in
birds, we compiled more than 400 immunological records of more than 100
avian species from about 100 previous studies that applied a standardised
protocol to measure haemolysis and haemagglutination. We extracted data on
15 life-history and ecological variables and built
phylogenetically-informed comparative models to determine how these
variables can explain variation in both immunological indices. We also
inferred evolutionary patterns by selecting the best-fitting
macroevolutionary models. Our comparative models indicated that several
ecological variables, including seasonal stage, sex, age, migration
distance, diet type, and climatic factors, and only one life-history
variable, body mass, were able to explain the immunological variation. The
best macroevolutionary models suggest that both immune indices evolved
largely through gradual divergence under strong phylogenetic constraints,
with evidence for stabilising selection within Passeriformes. Overall, our
results highlight the role of seasonal and demographic pressures,
alongside phylogenetic history, in shaping immune variation across avian
species.