Meeting Abstract
Female birds transfer immunoglobulin Y (IgY) to their eggs, which confer beneficial maternal effects on offspring growth and immune function. The specificities of these antibodies reflect the antigenic environments that females have experienced and likely correspond to antigenic challenges that offspring will encounter. Thus, females should be selected to deposit yolk IgY in accordance with antigenic pressure in the offspring environment. We have previously shown that active bird nests harbor diverse bacteria and that breeding birds respond to experimental modifications of these communities as evidenced through differential levels of maternal antibody deposition. Here we present results from a direct side-by-side test of the Antigen-Diversity and Antigen-Abundance Hypotheses to determine how each of these community characteristics contributes to variation in the total amount of yolk IgY deposited by female tree swallows (Tachycineta bicolor). Swallows exposed to reduced bacterial diversity during nest-building produced eggs and nestlings with lower levels of IgY than did control females, lending support to the Antigen-Diversity Hypothesis; nestlings from diversity-reduced nests also had lower plasma bactericidal activity than did control nestlings. However, we did not find support for the Antigen-Abundance Hypothesis because IgY levels of eggs and nestlings did not differ significantly between abundance-reduced and control groups. We also provide an overview of nest microbiome structure from metabarcoding data produced by Illumina sequencing of the 16S rRNA gene.
