Adaptation and latitudinal gradients in species interactions: nest predation in birds

Are rates of biotic interactions are stronger in the tropics? Here we investigate nest predation rates in birds, a canonical example of a strong tropical biotic interaction. Counter to expectations, daily rates of nest predation vary minimally with latitude. However, life history traits that influence nest predation have diverged between latitudes. For example, tropical species have evolved a longer average nesting period, which is associated with reduced rates of nest attendance by parents. Daily nest mortality declines with nesting period duration within regions, but tropical species have a higher intercept. Consequently, for the same nesting period length, tropical species experience higher daily nest predation rates than temperate species. The implication of this analysis is that the evolved difference between latitudes in nesting period length produces a flatter latitudinal gradient in daily nest predation than would otherwise be predicted. We propose that adaptation
may frequentl...