<p>Plant microbiomes are diverse communities of many microbial species. Growing evidence suggests that a complex network of interactions between members of the microbiome is necessary to maintain the health of host plants. Overall microbiome impacts can be difficult to predict and there is still much unknown about how taxonomic diversity links to function. All research on such dynamics so far has been limited to vascular plants, but the non-vascular bryophytes also have rich microbiomes and understanding these is a necessary component for understanding the evolution and ecology of plant microbiomes. This study takes advantage of the existing fungal endophyte culture collection for the model liverwort <i>Marchantia polymorpha</i> L. to begin expanding experiments on microbiome community interactions into bryophytes. This series of experiments reveals examples of synergy, interference, and priority effects in how fungal endophyte combinations impact <i>M. polymorpha</i>. These results constitute a foundation for the development of more complex synthetic community studies similar to those already existing for vascular plant models.</p>