Inbreeding depression in polyploid species: a meta-analysis

Whole-genome duplication (WGD) is a common mutation in eukaryotes with far-reaching phenotypic effects. Morphological and fitness consequences of WGD and their effects on the survival of novel polyploid lineages are intensively studied. Another important factor that may also determine the probability of establishment and success of polyploid lineages is inbreeding depression. Inbreeding depression is expected to play an important role in the establishment of neopolyploid lineages, their capacity to colonize new environments, and in the simultaneous evolution of ploidy and other life-history traits such as self-fertilization. Both theoretically and empirically, there is no consensus on the consequences of polyploidy on inbreeding depression. Here, we investigated the effect of polyploidy on the evolution of inbreeding depression by performing a meta-analysis within angiosperm species. The main results of our study are that the consequences of polyploidy on inbreeding depression are complex and depend on the time since polyploidization. We found that newly formed polyploid lineages have a much lower amount of inbreeding depression than their diploid relatives. Natural established polyploid lineages are intermediate, exhibiting a higher amount of inbreeding depression than synthetic neopolyploids, but smaller than diploids, suggesting that the negative effect of polyploidy on inbreeding depression decreases with time since polyploidization.