Microbiome interactions within the seed ecological spectrum

Background/Question/Methods

Trade-offs are a central theme involved in the maintenance of species diversity. In plants, a commonly understood trade-off between species includes seed size and seed mass, where a species can choose to invest in a ‘fast’ strategy, producing many small seeds to increase fecundity, or a ‘slow’ strategy, producing few large seeds to ensure offspring survival. A trait emerging as an essential metric in plant economic trade-offs is the ability of plants to associate with microbial symbionts, often using them to offset trade-off costs. Seed-associated microbes are thought to influence host phenotypic variation and thus the outcome of well-known trade-offs in seed investment. We hypothesize that plants investing in a ‘slow’ strategy, with large seeds and lower seed number, will invest more in the acquisition of singular specialist microbial symbionts and limit the recruitment of a diverse set of generalist microbial symbionts. To test this, we analyze publicly available datasets of seed microbiome studies and analyze seed microbial diversity metrics within known seed trait gradients.

Results/Conclusions

We find seed microbial alpha diversity exists within the seed size-number economic spectrum. Specifically, we find lower seed microbial diversity strongly correlates with larger seed size and lower seed number. These findings suggest plants that invest in ‘slow’ reproductive strategies recruit specific microbes to maintain seedling establishment post-germination. These findings help us understand microbial assembly rules of the seed microbiome across multiple plant species and how these communities might affect plant trait strategies. By understanding the seed microbiome as an important extended phenotype, we can leverage future microbiome data to create a predictive framework for seed economic space, plant investment, and overall ecological dynamics.