Processes of distribution

Abstract

An important part of the southern fauna not so far discussed are the terrestrial invertebrates of New Zealand. I wish to mention only two points relevant to this discussion. The first is to include New Zealand with Dr Darlington’s observations on the depauperate Tasmanian and Fuegian faunas. Despite a great variety of environments the New Zealand insect fauna, for example, has only about one quarter the number of species of Australia. Secondly, as to the derivation of the New Zealand invertebrates: valuable biogeographical data which have recently appeared in monographs by Lee on the N. Z. earthworm fauna, and Forster on the Opiliones emphasize a relatively recent northern element which arrived by land connexions of Tertiary times. Of the two Megascolecid families that make up the earthworm fauna the Megascolecinae are, in Lee’s view, a ‘younger’ element, Australian or Indo–Malayan in origin, while the ‘earlier' Acanthrodrilinae may he interpreted as being of northern or southern origin, though Lee supports a Cretaceous invasion from the North. A fuller knowledge of the soil, moss, and litter animals of Nothofagus forest throughout its range will be important in assessing the nature, and extent of the antarctic element in the New Zealand fauna. One of the many difficulties in considering the distribution of the outlying circumpolar flora and fauna is to account for variation in the distribution patterns. Professor Skottsberg has indicated that, as far as certain elements of the preglacial flora are concerned, the lines of distribution seem to radiate from the Antarctic. This seems to be equally true for certain terrestrial arthropods, but the lines do not radiate in all directions with regard to any one species. For example, the Ilburnia-Nesosydne complex traversed the Pacific through Juan Fernandez to Hawaii, and the South Atlantic to St Helena, but did not reach New Zealand and Australia (unless we recognize a single monotypic alohine genus ( Proterosydne ), known only from Queensland, as a derivative of this stock).