Evolution of subalpine and alpine plant groups in New Zealand

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Abstract
Although some of the plants of alpine and subalpine habitats in New Zealand are derived from ancestors that have been present since Paleogene, or possibly Cretaceous, times, many entered via Australia following the late Pliocene and subsequent elevation of mountains in Malaysia, New Guinea, Australia, and New Zealand. The New Zealand alpine and subalpine habitats only developed in the past few million years, during which they have been profoundly and repeatedly altered by Pleistocene glaciations and finally by man. As these habitats developed in isolation they were colonised mainly by plants derived from Australia, as a result of long-distance dispersal. Westward dispersal, in the face of the prevailing westerlies, is almost ruled out for Australasian plants. In New Zealand, many of them evolved rapidly to produce numerous species in consequence of the processes of adaptive radiation, interspecific hybridisation and recombination, and in many instances self-pollination. These large clusters of species, when compared with the relatively few members of the same groups in Australia, have previously led to the impression that the Australian representatives were derived from New Zealand. In fact, it seems to have been the unusual opportunities for rapid evolution, in response to a novel, isolated, and rapidly changing environment, that has led to the far greater representation of species in New Zealand.