Age of the alpine biota

[First paragraph...]
The suggestion that the New Zealand alpine biota is geologically young is not new, but has recently been revived in the light of developing ideas on Tertiary and Pleistocene climatic and topographic history (Fleming 1962 b). Cockayne was aware of the problems raised by evidence of very warm Tertiary climates and minimal land relief, and he suggested that a nucleus of plastic species, descended from a Cretaceous mountain flora, survived until the growth of mountains and cooling climate in the Pliocene allowed them to exploit the alpine environment once more. A history back to the time of the Cretaceous mountains is, however, unlikely because the mountains formed in the Early Cretaceous Rangitata Orogeny were already dwindling by the time angiosperms were distributed in the Later Cretaceous, and because there is no evidence that climatic conditions in New Zealand were suitable for the alpine biota at that time.