Synthesizing Existing Phylogenetic Data to Advance Phylogenetic Research in Orobanchaceae

Abstract To date, no comprehensive phylogenetic analyses have been conducted in Orobanchaceae that include both a wide sampling of genera and a large sampling of species. In addition, a lack of fossil evidence in the clade precludes the use of primary fossil calibrations for divergence time estimation, preventing the establishment of a comprehensive temporal framework for use in macroevolutionary studies. Here, we use a recently developed set of tools for synthesizing publicly available data, apply these to reconstruct a comprehensive timetree for Orobanchaceae, and then investigate diversification dynamics in this clade of mostly parasitic plants using two model based methods. The assembled supermatrix included more than 900 species, representing approximately 40% of the known species diversity of the family, and the resulting phylogeny largely confirmed relationships revealed in earlier studies; however, we identified ten non-monophyletic genera that will require focused systematic attention to resolve. Diversification rate analyses found substantial support for character-dependent diversification, with elevated rates in hemiparasitic clades, and evidence for a number of speciation rate changes throughout the tree that are likely linked to other traits. Importantly, our multi-state HiSSE (Hidden State Speciation and Extinction) analysis revealed that transitions to a parasitic lifestyle only occur when there is a prior transition in an unobserved precursor state. For Orobanchaceae, our study provides a new comprehensive framework for the clade that can serve as a stepping-stone for future macroevolutionary studies.