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bioRxiv · 10.64898/2026.10.22.761184

Ocean depth modifies host-microbiome ecology and evolution

Riesgo, A.·Montoya, J. M.·Thomas, T.·Turon, M.·Pita, L.·Lurgi, M.·Alvarez Fernandez, A.·Nielsen, S.·Diez-Vives, C.
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Abstract

A major unsolved question in ecology and evolution is how similar free-living and symbiotic microbial communities are. In marine systems, depth homogenises free-living communities due to stronger dispersal and weaker environmental filtering compared to surface waters. We show that symbiotic communities of marine sponges follow a different pattern, with a subset of sponge species mirroring the increased similarity with depth seen in their free-living counterparts, while others remain highly host-specific both in shallow and deep waters. Moreover, in deep waters, more phylogenetically similar hosts harbor more similar microbiomes, yet host-symbiont cophylogeny nearly vanishes. This reveals two contrasting eco-evolutionary assembly rules: in more constant environments like the deep sea, community assembly is driven by host and environmental filtering with minimal signature of coevolution, whereas in variable environments, like shallow waters, host-symbiont coevolution is strong and key to maintain host-specific microbiomes.

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Riesgo, A., Montoya, J. M., Thomas, T., Turon, M., Pita, L., Lurgi, M., Alvarez Fernandez, A., Nielsen, S., Diez-Vives, C.. 2026-10-23. Ocean depth modifies host-microbiome ecology and evolution. https://doi.org/10.64898/2026.10.22.761184

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