Arctic-Alpine species in the northern hemisphere are occasionally derived from Tertiary relict groups, but the genus Pyrola (Ericaceae) appears to be exceptional and lineages may have arisen multiple times. Liu et al. reconstruct the biogeographic history of Pyrola based on a phylogenetic analysis, and find that three circumboreal lineages have arisen independently, and at least two of these appear to have originated in Asia. The cool, high-altitude habitats of many Pyrola species together with the fact that diversification in the genus coincided with global cooling from the late Miocene onwards fits a hypothesis of pre-adaptation to become circumboreal within this group.
A study finds that three circumboreal lineages of Pyrola have arisen independently, and at least two of these appear to have originated in Asia.