Uncovering the reciprocal effects of plant polyploidy and the microbiome: implications for understanding of polyploid success

SummaryPolyploidy plays a major role in diversification and speciation of almost all plants. Separately, the microbiome is recognized for its ubiquitous role in plant functioning. Despite the importance of both processes, we lack a synthetic picture of their reciprocal relationship. I forge this missing linkage by presenting the ways in which plant polyploidy can shape the microbiome and how the microbiome in turn can affect polyploid phenotype and fitness. I illustrate these interactions by drawing on the small, but compelling, set of comparisons of the plant–microbial community interaction with taxa representing different stages of the polyploid continuum and thereby shed light on how the advantages of polyploidy may be influenced by microbes. I use findings from a range of studies to build the case for plant–microbiome reciprocal interactions in both key pathways for polyploid persistence: overcoming their minority cytotype disadvantage and increasing competitive ability and/or niche shifts relative to diploids. I put forward how the microbiome likely plays a role in polyploid stress tolerance, abiotic niche breadth, range limits and coexistence. I conclude by identifying the research needed to test these hypotheses and how doing so could transform our understanding of polyploidy as a driver of plant ecology and evolution.