Feather Microbiota Landscapes: Biogeography and Phenology Shape Feather Microbiota Traits in a Migratory Seabird in a Subantarctic Ecosystem

It is known that phenological changes (i.e., behavioural and sometimes morphological and physiological traits that repeat annually) influence the wildlife gut microbiota. However, it remains largely unknown to what extent geographic variation could modulate the effect that phenology has on wildlife microbiota. Here, we analysed the feather microbiota in adult Magellanic penguins (Spheniscus magellanicus) and the microbes from samples of nest soil and seawater, using Illumina MiSeq sequencing of bacterial 16S rRNA (V3-V4 variable region) at three phenological stages (courtship, egg-laying and chick-rearing) across five nesting colonies with environmental heterogeneity, in the Magellan Strait, Chile. We found over 67,000 ASVs, most belonging to the bacterial family Moraxellaceae. We detected seven core bacterial genera despite geographic and phenological variation; among them, Psychrobacter had the highest relative abundance. Phenology affected feather microbiota alpha diversity and the relative abundance of selected genera in a colony-specific fashion. Still, it consistently affected feather and nest soil microbial composition, highlighting a phenological microbial succession pattern in penguin feathers and nest soil. From the geographic perspective, we detected three main results in the penguin feather microbiota: (1) alpha diversity was higher in the largest colonies, although only in the chick-rearing stage; (2) a significant distance-decay pattern, in the egg-laying and chick-rearing stages; and (3) compositional clusters that follow the geographic location of each colony. Our results highlight how temporal and environmental heterogeneity shape microbial traits in marine wildlife.