The origins and diversification of hummingbird pollination in Bromeliaceae

Elizabeth Anne Forward, Jamie B Thompson 

Bromeliaceae are a model group for understanding explosive Neotropical diversification, combining remarkable ecological breadth and high species richness, despite relatively recent evolutionary origins. Multiple drivers are hypothesised to accelerate bromeliad diversification, and hummingbird pollination is frequently proposed to be among the strongest. However, our understanding has been limited by sparse and uneven pollinator datasets and by the amount of diversification rate variation in bromeliads, much of which can be explained by other drivers. Here we assemble a novel database of published pollinators for 403 bromeliad species spanning 70% of genera across all subfamilies and analyse these data in a phylogenetic framework. We estimate ancestral states, which indicate widespread lability, including previously unknown transitions. Many of these occur in recent evolutionary time, indicating ongoing turnover in pollinators. Despite pronounced background diversification rate heterogeneity, we confirm hummingbird pollination to be a primary driver of diversification, a result that we show is unlikely to change even under unrealistic assumptions of its prevalence in unsampled species. Our findings support hummingbirds as a central organising force in the complex web of bromeliad evolution and provide a foundation for future data collection and integrative analyses in this charismatic family.