Phylosymbiosis is the idea that the relationships among host species are mirrored in the relationships among their microbiomes—that is, closely related hosts harbor more similar microbial communities. This matters because it points to evolutionary history as a force shaping microbiomes, suggesting that host traits and microbiome assembly are not random but partly predictable.

At the same time, the strength of phylosymbiosis varies across vertebrate clades, and microbiomes are highly variable within species. This variability means phylosymbiosis is not a universal rule but rather a window into when and why host–microbiome associations are conserved, and when ecological or environmental factors override evolutionary signals.

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Questions: 

• How do host traits, like diet or physiology, shape patterns of phylosymbiosis?

• Why is phylosymbiosis strong in some animal groups but weak in others?

• When do ecological pressures—like climate, habitat, or pathogens—override evolutionary signals in the microbiome?

• How does the composition of host species in a community influence patterns of phylosymbiosis?

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1. Brown BRP, Goheen JR, Newsome SD, Pringle RM, Palmer TM, Khasoha LM, Kartzinel TR. 2023. Host phylogeny and functional traits differentiate gut microbiomes in a diverse natural community of small mammals. 2023. Molecular Ecology 10.1111/mec.16874

2. ​Kartzinel TR, Hsing J, Musili PM, Brown BRP, Pringle RM. 2019. Covariation of diet and gut microbiome in African megafauna. Proc. Nat. Acad. Sci. US. 10.1073/pnas.1905666116

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