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# of Endemic Species
811: New Zealand
Major Habitat Type:
temperate coastal rivers
Lindsay Chatterton, The Nature Conservancy
New Zealand lies in the southwestern Pacific Ocean and encompasses the North Island and South Island, as well as Waiheke Island, Great Barrier Island, Stewart Island/Rakiura Island, and the Chatham Islands. The ecoregion also includes the Auckland Islands and Campbell Island. Within the ecoregion there are three areas of biogeographic distinction, including the northern North Island, central New Zealand, and southern New Zealand. The northern North Island sub-ecoregion consists of the landmass north of the Auckland isthmus. Its southern boundary includes all of the catchments draining Kaipara harbor. The central New Zealand sub-ecoregion is the largest and most geologically diverse unit, and includes all of the catchments entering the Hauraki Gulf. It could arguably be separated into two separate units, although defining a possible boundary within the central portion of the North Island is difficult due to the loss of most freshwater biological evidence. The southern New Zealand sub-ecoregion includes the eastern coast of the South Island from the Hapuku and Kahutara rivers in the north, to Stewart Island in the south, and the Chatham Islands in the east.
Drainages flowing into:
Drainages of the ecoregion flow into the Pacific Ocean and Tasman Sea.
Main rivers or other water bodies:
The longest rivers in New Zealand include the Waikato River (425 km), Whanganui River (290 km), and Rangitikei River (241 km) in the North Island, and the Clutha River (322 km) and Taieri River (288 km) in the South Island. The three largest lakes in the ecoregion include Taupo, Te Anau, and Wakatipu. The largest of these, Lake Taupo, is drained by the Waikato River and is volcanic in origin. During glacial maxima the catchments of the Hauraki Gulf, Little and Great Barrier Islands, and the Coromandel Peninsula are likely to have been connected to watersheds flowing from the Hauraki plains that at times included the Waikato River (Manville and Wilson 2004). In the lower North Island, geological and genetic evidence indicates that the Tukituki, Manawatu, and Ruamahanga rivers were once linked. Rivers in southern New Zealand include the Hapuku and Kahutara that drain the southeastern slopes of the Seaward Kaikouras.
New Zealand lies on the boundary of the Pacific and Australian plates and has a rich tectonic and volcanic history. The northern North Island is centered around a chain of ancient Pliocene islands (7-4 million years (Ma) ago) that have since been connected to the central North Island by sand, volcanic activity, and changes in sea level (Morgan-Richards et al. 2001). The area has been relatively free of major disturbances that mark southern and central New Zealand, although volcanism has had an intermittent influence during the Pleistocene, with localized basaltic eruptions occurring in northeastern Northland as recently as 1300 years ago (Leathwick et al. 2004).
The northern part of central New Zealand contains both the andesitic volcanoes of Taranaki and Tongariro, and the rhyolitic Taupo Volcanic Zone. Eruptions from the latter generally consisted of high-energy, ignimbrite flow material and air-fall tephra deposits. Over the last 50,000 years over thirty-six significant tephra events have been recorded. The largest of these would have affected most of the central and lower North Island and northeastern South Island (Leathwick et al. 2003).
The southern and eastern side of the central New Zealand sub-ecoregion is marked by another area of major historic disturbance, but here glaciation rather than volcanism was the major biogeographic driver. The Southern Alps (highest point at 3754 m) runs lengthwise down the middle of the South Island and forms a natural dispersal barrier between east and west coast rivers. During major glacial periods ice cover at higher elevations was extensive and thought to have occurred almost continuously from Nelson Lakes in the north to southern Fiordland (Leathwick et al 2004). Ice also descended to form piedmont glaciers that covered much of the coastal plain in Westland (Soons 1982), an area devoid of non-diadromous fish species.
The southern New Zealand sub-ecoregion encompasses a topographically and environmentally diverse part of New Zealand, including eastern slopes of high elevation mountains along the Southern Alps, lower elevation hill country and mountains further east, and extensive inter-montane basins and plains of glacial and/or alluvial origin (Leathwick et al. 2003).
The climate of this ecoregion varies from subtropical in the north to cool temperate in the south, with alpine conditions in the Southern Alps. In the northern North Island impacts during the last glacial maximum were relatively muted, with forest cover prevailing during this period.
The terrestrial habitats in this ecoregion are diverse, and span four biomes, including temperate broadleaf and mixed forests in the north and west; temperate grasslands, savannas, and shrublands in the southeast; montane grasslands in the Southern Alps; and tundra in the Subantarctic islands. Within these biomes are twelve terrestrial ecoregions, including the North Island temperate forests, South Island temperate forests, Fiordland temperate forests, Rakiura Island temperate forests, Westland temperate forests, Northland temperate kauri forests, Nelson Coast temperate forests, Richmond temperate forests, Westland temperate forests, Cantebury-Otago tussock grasslands, South Island montane grasslands, and Antipodes Subantarctic Islands tundra.
The relatively depauperate New Zealand native fish fauna is dominated by Galaxiidae, with Eleotridae the second most common group. Over 85% are endemic to New Zealand and there is also an unusually high level of diadromy, with almost half of the species requiring passage to and from the sea during parts of their lifecycle. Consequently, there is a core of species that are widespread, and biogeographic patterns are best illustrated by the non-diadromous species.
The fish fauna of the northern North Island is dominanted by diadromous species, and only four non-diadromous species are recorded, although two are regionally endemic. The extent of volcanic disturbance in central New Zealand is such that populations of non-diadromous fish and crayfish are rare or absent, particularly where the effects of rhyolitic ignimbrite eruptions were most severe (McDowall 1996). During the last glacial maximum the coastal plain along the Manawatu Coast extended across the northern entrance to Cook Strait to provide a connection with the northern South Island. Distribution patterns of the brown mudfish (Neochanna apoda) and the crayfish Paranephrops planiforms, and genetic relationships across populations of dwarf galaxias (Galaxias divergens) and upland bully (Gobiomorphus breviceps) support a connection between southern and eastern North Island and northwestern South Island drainages during this and previous glacial periods (Allibone 2002; Smith et al. 2005).
In southern New Zealand the high elevation western mountains were extensively affected by glaciation during the last glacial maximum, whereas lower elevation units to the east had minimal ice cover. These areas are thought to have provided refugia for a diverse and distinctive collection of non-diadromous galaxiid fish (Waters & Wallis 2001). The eastern region is the center for non-diadromous galaxiids, with as many as ten species only found in streams in eastern South Island and Stewart Island. Some of these include Galaxias anomalus, G. pullus, G. gollumoides, G. eldoni, G. depressiceps, G. cobitinis, G. macronasus, and Canterbury mudfish (Neochanna burrowsius). Furthermore, three other species (the common river galaxias (Galaxias vulgaris), longjawed galaxias (G. prognathus), and alpine galaxias (G. paucispondylus)) have distributions centered in this region, with occasional populations found in neighboring catchments of northwestern South Island, the northern limit of these species. These species occur at only a few sites, and their presence is thought to be representative of historic catchment linkages (Waters & Wallis 2000).
There is compelling evidence that Stewart Island was also connected to the mainland South Island during periods of lower sea levels (e.g. 6-8000 year ago). The island fish fauna is dominated by common mainland diadromous species (Chadderton 1988). Waters & Wallis (2001) have documented strong genetic similarities between two of the three non-diadromous fish species recorded, a pattern matched by two freshwater isopod species common to Stewart Island and eastern South Island (McGaughan et al. 2005).
Description of endemic fishes:
The archipelago has been isolated from Australia for over 80 million years. The fauna and flora show high levels of endemism and radiation among groups, many of which are thought to be ancient lineages, although recent debate suggests that the biotas’ origin may be more recent and the result of colonization after New Zealand emerged from the sea since the early Miocene (25 Ma: Trewick et al 2007). Endemics are dominated by the genera Galaxias, Gobiomorphus, and Neochanna. Two widespread endemic diadromous species, black flounder (Rhombosolea retiaria) and giant kokopu (Galaxias argenteus), are noticeably absent in the northern North Island, as is dwarf galaxies (G. divergens), the most widespread non-diadromous species.
Other noteworthy aquatic biotic elements:
The northern North Island is considered a region of high mayfly diversity (Towns 1987, Collier 1993), but has low caddisfly and stonefly diversity (Henderson 1985, McLellan, 1990). The Auckland isthmus appears to be a major barrier to dispersal of aquatic insects. (Smith & Collier 2001; Smith et al. 2006).
Justification for delineation:
For New Zealand and other islands and island groups, islands were placed in ecoregions on the basis of expert input.
Collier, K. (1993). "Review of the Status, Distribution, and Conservation of Fresh-Water Invertebrates in New-Zealand" New Zealand Journal of Marine and Freshwater Research 27(3) 339-356.
Leathwick, J. R., Collier, K., et al. (2003) "Identifying Freshwater Ecosystems with Nationally Important Natural Heritage Values: Development of a Biogeographic Framework". Hamilton, New Zealand. National Institute of Water & Atmospheric Research Ltd.
McDowall, R. M. (1996). "Volcanisms and freshwater fish biogeograpny in the northeastern North Island of New Zealand" Journal of Biogeography 23 139-148.
McLellan, I. D. (1990)"Distribution of stoneflies in New Zealand" In Camplbell, I.C. (Ed.). Mayflies and stoneflies. (pp. 135-140) Dordrecht, Netherlands: Kluwer Academic Publishers.
Towns, D. R. (1987). "The mayflies (Ephemeroptera) of Great Barrier Island, New Zealand: macro- and micro-distributional comparisons" Journal of the Royal Society of New Zealand 17 349-361.