Himalayan-Tibetan Plateau Uplift Drives Divergence of Polyploid Poppies: Meconopsis Viguier (Papaveraceae)

Abstract

Meconopsis Viguier (Papaveraceae) is an iconic genus of alpine forbs that includes medicinal and ornamental species. This study extends previous phylogenetic analyses of Meconopsis, using ITS sequences representing all the major Meconopsis clades. Phenotypic traits are also analysed for all described species. Our results show that Meconopsis evolved as a ≥ octaploid clade, with considerable interior structure reflecting further changes in ploidy levels as well as phenotypic differentiation. We support the exclusion of a few species as Cathcartia or Papaver, making Meconopsis a Tibetan region clade. Based on average rates of nucleotide substitution in angiosperm herbs we estimate that the Meconopsis clade diverged from the Meconella clade of Papaver approximately 16.6 Ma. This is soon after the 'hard' collision of the Indian continent with Asia caused uplift of the Himalaya and Hengduan ranges, greatly extended the Tibetan plateau, and initiated monsoonal climates. Eight major clades within Meconopsis are well supported and these correspond closely to previously recognised subgenus groups. However, the relationship among the clades is poorly resolved, probably because they diverged rapidly ∼15-11 Ma. Two of these clades are ∼dodecaploid but appear to have originated independently. The eight clades have distinct distributions, variously associated with the Himalaya, the eastern Plateau and Hengduan ranges. Some Meconopsis species were not monophyletic, suggesting that a combination of multilocus molecular and phenotypic traits is required when defining and revising species.