Widespread evolution of poricidal flowers: A striking example of morphological convergence across flowering plants

Abstract

SummaryThe evolution of tube-like floral morphologies that control pollen release via small openings (functionally poricidal flowers) represents a taxonomically and geographically widespread instance of repeated and independent evolution of a functionally similar morphology. Poricidal flowers are often closely associated with buzz pollination by bees, but we lack an updated angiosperm-wide survey of their phylogenetic distribution.We identify all presently known angiosperm genera containing poricidal flowers via a literature survey. We determined the phylogenetic distribution of poricidal flowers and minimum number of independent gains and losses via a genus-level and species level angiosperm-wide phylogeny. We estimated if evolution of poricidal flowers is associated with changes in speciation/extinction via diversification rate analyses.Poricidal flowers occur across at least 87 angiosperm families and 635 genera containing > 28,000 species. At the genus level, more than 200 independent gains and 145 independent losses of poricidal flowers occurred. Across angiosperms, genus-level analyses suggest poricidal flower evolution is associated with lower net diversification rates (origination-extinction). Species-level analyses argue no diversification linked to poricidal morphology but within the two focal families we found family-specific diversification effects.We present different hypotheses for the functional significance of poricidal flowers, including its association with buzz pollination, and suggest future directions for studies elucidating the extent to which morphological and functional convergence of poricidal flowers are correlated.