Meeting Abstract
The microbial communities that reside on animals are dynamic and can be affected by the behavior and physiology of the host. These microbial communities provide critical functions to their host, but can also represent health costs if they are pathogenic. In birds, bacteria residing in the cloaca form a complex community because it is composed of transient gut bacteria as well as sexually transmitted bacteria. During the breeding season there is an increase in physical contacts among individuals, testosterone levels increase in males, and there are additional energetic demands, all of which can increase exposure to bacteria or facilitate infection. As such, we hypothesized that cloacal bacterial communities would be more diverse during the breeding season than in the non-breeding season, males would have more diverse cloacal bacterial communities than females, and that individuals would accumulate bacterial species across breeding seasons. We surveyed the cloacal microbial communities in free-living male and female rufous-collared sparrows (Zonotrichia capensis) through sequential breeding and non-breeding seasons. We found that the cloacal microbiome was different between the sexes, and that in males, but not in females, the bacterial community became more diverse with the onset of reproduction, increasing its phylogenetic diversity and OTU richness, and then decreased its diversity as they transitioned to a non-breeding condition. Individuals sampled across sequential breeding seasons did not accumulate more bacterial species or change their community composition compared to their previous season. Among males, those with higher testosterone levels during their breeding season, had a more phylogenetically diverse cloacal microbiome. This study showed that the cloacal microbiome in birds is dynamic and responsive to breeding condition and sex of the host.
