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Sister Species an Ocean Apart: Investigating the drivers of coral reef fish microbiome composition across the Isthmus of Panama
Laura L. Lardinois, Natasha Hinojosa, Caitlin McNally, Javiera Mora, Rowan Barrett, Matthieu Leray
Three million years ago, the rise of the Isthmus of Panama caused dramatic environmental shifts that set populations of coral reef organisms on separate evolutionary trajectories. Organisms separated by the Isthmus adapted to different environments, forming pairs of sister species. The microbes that interact with these sister species adapted in tandem with their hosts, creating an unparalleled natural experiment to understand the evolution of host-microbe interactions. We investigate the ecological and evolutionary factors driving microbiome composition using seven pairs of sister reef fish species in Panama. We expected the fishes’ skin microbiome to cluster by ocean, being shaped primarily by the surrounding environment, whereas the gut microbiome – which is known to respond to host diet and phylogeny – would be more strongly driven by host species, such that sister fish gut microbiomes would be more similar. We find evidence for the importance of the host in structuring both skin and gut microbial communities, suggesting long-lasting and important symbioses. However, as predicted, gut microbiomes were more strongly linked to host species than skin microbiomes, likely due to greater host control coupled with the selectivity of the internal gut environment. Gut microbiomes were more similar across species within dietary strategies and between sister species pairs, indicating that shared host traits play a role in structuring microbiomes. These sister fish species and their unique evolutionary histories are an ideal system to expand our understanding of host-microbe interactions and, consequently, our ability to protect the diversity of organisms faced with rapid environmental change.
