The microbiome of Calasterella californica is shaped mostly by the genetics of the host thalli

Premise of the study: Plant microbiomes have been shown to affect essential life processes like plant growth, defense mechanisms, and stress responses. Much of the work done on this topic has focused on vascular plants and model organisms. Liverwort biology is very different from that of vascular plants, making generalizations difficult. Here we characterize the microbiome of the liverwort Calasterella californica and explore whether climatic, geographic, and genetic factors are potential drivers of the microbiome composition. Methods: We utilized the genomic data obtained through the California Conservation Genomics Project, which densely sampled individuals of C. californica across California. We selected 34 samples and utilized the MetaPhlAn pipeline to characterize the composition of the microbial communities for each sample. Key results: We characterize the core microbiome of Calasterella, which is dominated by Methylobacterium. There is a weak association between the relative abundance of bacteria in the Hyphomicrobiales and liverwort size. Genetic distance was the most important factor in shaping beta diversity of the Calasterella californica microbiome. Environmental distance was only weakly predictive and geographic distance was not significant. Conclusions: Leveraging genomic data obtained from field samples of a liverwort species allowed us to characterize the microbial diversity of C. californica and its variation across space. There is a group of taxa that are consistently associated with this plant. And the variation observed across samples seems to be linked to the genetic similarity of the liverworts.