Ecological and life-history factors influencing the evolution of maternal antibody allocation: a phylogenetic comparison

Abstract

Maternally derived yolk antibodies provide neonates with immune protection in early life at negligible cost to mothers. However, developmental effects on the neonate's future immunity are potentially costly and thus could limit yolk antibody deposition. The benefits to neonatal immunity must be balanced against costs, which may depend on neonate vulnerability to pathogens, developmental trajectories and the immunological strategies best suited to a species' pace of life. We measured yolk antibodies and life-history features of 23 species of small Neotropical birds and assessed the evidence for each of several hypotheses for life history and ecological effects on the evolution of yolk antibody levels. Developmental period and yolk antibodies are negatively related, which possibly reflect the importance of humoral immune priming through antigen exposure, and selection to avoid autoimmunity, in species with a slower pace of life. There is also a strong relationship between body size and yolk antibody concentration, suggesting that larger species are architecturally equipped to produce and transfer higher concentrations of antibodies. These results suggest that developmental effects of maternally derived antibodies, such as imprinting effects on B-cell diversity or autoimmune effects, are important and deserve more consideration in future research.

Figure 1.

Life-history predictors of yolk IgY deposition. Points are species means±s.e. (a) Incubation period is strongly negatively related to yolk IgY deposition, even if the common tody-flycatcher (T. cinereum, incubation period of 23 days) is excluded. Marker shade is coded by the nestling period, darker colours correspond to longer nestling periods. (b) Nestling period is also negatively related to yolk IgY deposition, again, even with the exclusion of the extreme value of the grey-breasted martin (P. chalybea, nestling period of 28 days). Marker shade corresponds to incubation period. (c) Adult body mass is positively related to yolk IgY deposition. (d) Predictive surface showing the relationship between incubation period, nestling period and mass corrected yolk [IgY], generated without the two extreme value species.