LEE, Kelly A.; WIKELSKI, Martin; HASSELQUIST, Dennis; Princeton University; Princeton University; Lund University, Sweden: Sex Influences Immune Responses Differently in the House Sparrow and a Monomorphic Congener, the Eurasian Tree Sparrow

Seasonal and sex differences in immune responses have been well-documented in mammals but less extensively in other vertebrates. Sex differences in immune responses are expected to accompany differing life history strategies: due to highly variable reproductive success, males are expected to invest in current reproduction at the cost of survival, while females, with less variable reproductive success, are expected to invest more in survival, and thus immune defenses. Life history theory suggests that the magnitude of sex differences in investment in immune defenses should vary with the degree of sex-specific investment in traits under sexual selection. Here we test whether the monochromatic Eurasian Tree Sparrow, Passer montanus , exhibits smaller differences in immune defenses between the sexes than does the dimorphic House Sparrow, P. domesticus .