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

Polyploidy 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.