Cenozoic formation and colonisation history of the New Zealand vascular flora based on molecular clock dating of the plastid rbcL gene

A colonisation history for 411 extant genera and 477 lineages of the vascular flora of New Zealand was constructed using the plastid rbcL gene. Molecular clock crown ages suggest that the Eocene-Oligocene transition extinction at 33.9 Ma was critical to the development of the extant flora as few lineages, mostly ferns and conifers, predate this event. Based on crown dates, almost all extant angiosperm lineages have established after the Eocene-Oligocene transition extinction. The Oligocene marine transgression had little discernible impact on the formation of the extant flora, as at the culmination of the inundation (22.0–25.0 Ma) fifty extant lineages of vascular plant were present and another eight lineages originated during this time. The majority of extant species (89%) originated after the end of the Miocene Thermal Optimum at about 15.0 Ma. Nearly 50% of the extant species have evolved during mountain uplift and glaciation of the late Pliocene-Pleistocene (0–4.99 Ma). Therefore, despite a residual contribution from the Eocene, Oligocene and early to mid Miocene periods, the New Zealand vascular flora essentially originated in the late Miocene and after.