Phylogeny and the Evolution of Floral Diversity in Pedicularis (Orobanchaceae)

Pedicularis has a conflicted infrageneric taxonomic history in which floral and vegetative characters have alternately been interpreted as primary indicators of common ancestry. Recent classifications favor subgenera delimited by similarity in leaf arrangement, on the basis of the premise that corolla morphology has been subject to pollinator‐mediated selection, resulting in the convergent evolution of specialized floral forms from generalized ancestors. In this study, molecular phylogenetic analysis of Pedicularis reveals a low concordance of robust clade support and taxonomic groups. Nevertheless, the basic premise of higher homoplasy in floral characters relative to leaf arrangement is confirmed, although the hypothesized direction of change (from short‐tubed, beakless, toothed corollas to long‐tubed, beaked, toothless forms) is not uniformly upheld. In spite of the high evolutionary lability of floral form in Pedicularis, some character state combinations are rarely or never observed, suggesting functional constraints. Correlation analysis shows a significant association between curved‐rostrate corollas (a marker for nectar production) and long corolla tubes, indicating that access to nectar by pollinators has acted as a constraint on the evolution of corolla tube length.