Understanding polyploid establishment: temporary persistence or stable coexistence?

Polyploidy, resulting from whole-genome duplication (WGD), is ubiquitous in nature and reportedly associated with extreme environments and biological invasions. However, WGD usually comes with great costs, raising questions about the establishment chance of newly formed polyploids. The surprisingly high number of polyploid and mixed-ploidy species observed in nature may be a consequence of their continuous emergence or may reflect stable polyploid persistence and even coexistence with the ancestral ploidy under certain circumstances. However, empirical studies on contemporary polyploid establishment often neglect the cost-benefit balances of polyploid characteristics, tradeoffs between phenotypic characteristics, intercytotype interactions, recurrent polyploid formation, and stochastic processes. Here, we advocate for considering population-level success, combining the aforementioned factors that affect polyploid establishment and long-term coexistence with their ancestors. We approach the paradox of polyploid establishment despite high costs from a modern coexistence theory perspective and give an overview of the diversity of mechanisms and their timing that may potentially enable stable rather than transient persistence.