Reproductive complexity, whole genome duplication, and genome size data across vascular plants

Whole genome duplication (WGD) may be an important factor in plant macroevolution, implicated in diversification rate shifts, structural innovations, and increased disparity. But general effects of WGD on plant evolution are challenging to evaluate, in part due to the difficulty of directly comparing morphological patterns across clades. We explored relationships between WGD and the evolution of complexity across vascular plants using a metric based on the number of reproductive part types. We used multiple regression models to evaluate the relative importance of inferred WGD events, genome size, and a suite of additional variables relating to growth habit and reproductive biology in explaining part type complexity. WGD was a consistent predictor of reproductive complexity only among angiosperms. Across vascular plants more generally, reproductive biology, clade identity, and the presence of bisexual strobili (those that produce microsporangiate and megasporangiate organs) were better predictors of complexity. Angiosperms are unique among vascular plants in combining frequent polyploidy with high reproductive complexity. Whether WGD is mechanistically linked to floral complexity is unclear, but we suggest widespread polyploidy and increased complexity were ultimately facilitated by the evolution of herbaceous growth habits in early angiosperms.