BIOGEOGRAPHY OF AQUATIC INSECTS IN NEW ZEALAND

Abstract

There a re few publications on this subject and only two taxa have been well covered. PLECOPTERA Although there is little published on Plecoptera I am able to use tha t plus what I am currently working on to give some idea what possibly has occurred and is occurring in New Zealand. Mention of the origin of our fauna is first necessarv. The sole representatives of their families, Austroperla cyrene and Stenoperla prasina, are widespread throughout New Zealand. I consider them to be developed from recent wind drif t invaders from Australia where very similar sister species a re found. The notonemourids also appear to have arrived via Australia but earlier than the two species mentioned above. The Spaniocerca group is possibly prePleistocene and the Notonemoura group during or postPleistocene. Zelandobius (which is now not considered a gripopterygid) has sister genera only in South America, and like the gripopterygids which constitute the bulk of our stoneflies, has probably entered New Zealand via Antarctica. In New Zealand the notonemourids, gripopterygids and Zelandobius show no endemism in the North Island apar t f rom one forin of gripopterygid species. There is, however, considerable endemism in the South Island, Stewart Island, the Snares, Campbell Island and the Auckland Islands. Restricted species exist i n areas like Fiordland and NW Nelson which are considered to have been Pleistocene refugia. Most species of Zelandobius and Gripopterygidae, endemic to alpine and subantarctic biotopes, a re wingless. These wingless species a re generally so closely related to winged species that i t is difficult to find differences apart from characters which change with winglessness, o r a re adaptations to niore severe conditions. The North Island's only endemic is a n alpine brachypterous form of Aucklandobius fulvescens found in the Tararua Mountains. This species is common in both islands bu t has not been found as a brachypterous form in the South Island. I t must have invaded a niche lef t vacant in the north which would be filled by other species in the south. The stoneflies of the Auckland and Campbell Islands a re endemic griptopterygids, obviously New Zealand derived from the Apteryoperla-Aucklandobius complex. Those from the Auckland Islands exhibit adaptive radiation from two ancestors. One group consisting of a winged species with aquatic larvae, a stout apterous