FNZ 37 - Coleoptera (Insecta) - Popular Summary
Klimaszewski, J; Watt, JC 1997. Coleoptera: family-group review and keys to identification. Fauna of New Zealand 37, 199 pages.
( ISSN 0111-5383 (print), ; no. 37. ISBN 0-478-09312-8 (print) ). Published 15 Aug 1997
Beetles are the largest order of organisms, comprising over 350 000 described species in the world fauna. These species are classified in some 23 000 genera. It has been estimated that there are more species of beetles than there are of vascular plants or fungi, and 90 times as many as there are mammal species.
In New Zealand at least 5223 native species of beetles have been recognised. A further 356 species are either self-introduced or have been deliberately brought in, for example for the biological control of noxious weeds. These beetles belong to some 1100 genera in 82 families. By comparison the vascular plant flora includes about 2500 species, and the terrestrial vertebrate fauna about 350 species. The actual number of beetle species in New Zealand is undoubtedly much higher many are undescribed.
The first European collections of New Zealand beetles were made by Joseph Banks and Daniel Solander during Captain James Cook's first voyage, in 1769, and the first formal descriptions were by Johannes Fabricius in 1775.
The origin of New Zealand's beetles is essentially unknown, but apparently at least some had developed on an ancient land mass of continental origin which became increasingly isolated since the late Mesozoic era. The earliest known beetle fossil from New Zealand is of an incomplete front wing dating from the Cretaceous.
Four factors are responsible for the composition and diversity of the present-day beetle fauna of New Zealand.
- The origin of some of our fauna on the ancient southern supercontinent known as Gondwana.
- The estimated 80 million years of geographic isolation of New Zealand, which has resulted in some 90 percent endemism (local origin) of species, and high endemism also at genus level.
- Changing climate, land areas, and land surfaces due to factors such as glaciation, mountain building, and volcanic activity.
- The absence of mammals and other animals and plants which have dominated ecosystems elsewhere in the world.
The flora and fauna have been greatly modified in the last 1000 years by humans, who brought devastation to native forest and introduced exotic animals with destructive influence (e.g., deer, rats, possum, goats).
Contemporary New Zealand beetles are thus a composite of ancient, variously changed lineages, elements introduced by dispersal over short and long distances, and species intentionally and accidentally introduced by humans. The majority of species are associated with native forest, which now constitutes only 23 percent of the total land area. The shrinking forest has profoundly reduced the population size of many native species and their potentia1 for long-term survival.
Our beetles are also vulnerable to introduced organisms: their defence mechanisms are often ineffective against the new arrivals. They may succumb to competition for food with introduced wasps, to predation by mammals, and to depletion of food sources by weeds out-competing native plants. A number of beetle species are recognised as being threatened with extinction, and are listed for protection by the Department of Conservation.
On a positive note, beetle diversity can be unexpectedly high in relatively small areas of habitat. The beetle fauna of the Auckland suburb of Lynfield has been shown to exceed 1000 species, of which three-quarters are native.