|
The New Zealand wrens are a family (Acanthisittidae) of tiny passerines endemic to New Zealand. They were represented by six known species in four or five genera, although only two species survive in two genera today. They are understood to form a distinct lineage within the passerines, but authorities differ on their assignment to the oscines or suboscines (the two suborders that between them make up the Passeriformes). More recent studies suggest that they form a third, most ancient, suborder Acanthisitti and have no living close relatives at all. They are called "wrens" due to similarities in appearance and behaviour to the true wrens (Troglodytidae), but are not members of that family. New Zealand wrens are mostly insectivorous foragers of New Zealand’s forests, with one species, the New Zealand rockwren, being restricted to alpine areas. Both the remaining species are poor fliers and four of the five extinct species are known to or are suspected of having been flightless (based on observations of living birds and the size of their sterna); along with the long-legged bunting from the Canary Islands, they are the only passerines known to have lost the ability to fly. Of the species for which the plumage is known they are drab coloured birds with brown-green plumage. They form monogamous pair bonds to raise their young laying their eggs in small nests in trees or amongst rocks. They are diurnal and like all New Zealand passerines, for the most part, are sedentary. New Zealand wrens, like many New Zealand birds, suffered several extinctions after the arrival of humans in New Zealand. Two species went extinct after the arrival of the Māori and the Polynesian rat, and are known today only from fossil remains; a third, the Stephens Island wren, went extinct on the main islands, surviving only as a relict population on Stephens Island in the Cook Strait. This species and the bush wren became extinct after the arrival of Europeans, with the bush wren surviving until 1972. Of the two remaining species, the rifleman is still common on both the North and the South Islands, while the New Zealand rockwren is restricted to the alpine areas of the South Island and is considered vulnerable. ==Taxonomy and systematics== The taxonomy of the New Zealand wrens has been a subject of considerable debate since their discovery, although they have long been known to be an unusual family. In the 1880s, Forbes assigned the New Zealand wrens to the suboscines related to the cotingas and pittas (and gave the family the name Xenicidae). Later, they were thought to be closer to the ovenbirds and antbirds. Sibley’s 1970 study comparing egg-white proteins moved them to the oscines, but later studies, including the 1982 DNA-DNA hybridization study, suggested the family was a sister taxon to the subocines and the oscines. This theory has proven most robust since then, and the New Zealand wrens might be the survivors of a lineage of passerines that was isolated when New Zealand broke away from Gondwana 82-85 million years ago (Mya),〔Ericson P, Christidis L, Cooper, A, Irestedt M, Jackson J, Johansson US, Norman JA. (2002). A Gondwanan origin of passerine birds supported by DNA sequences of the endemic New Zealand wrens. ''Proc Biol Sci''. 269(1488):235-41.〕 though a pre-Paleogene origin of passerines is highly disputed and tends to be rejected in more recent studies. As no evidence indicates passerines were flightless when they arrived on New Zealand (that apomorphy is extremely rare and unevenly distributed in Passeriformes), they are not required by present theories to have been distinct in the Mesozoic. As unequivocal Passeriformes are known from Australia some 55 Mya, the acanthisittids' ancestors likely arrived in the Late Paleocene from Australia or the then-temperate Antarctic coasts. Plate tectonics indicate that the shortest distance between New Zealand and those two continents was roughly 1,500 km (1,000 miles) at that time. New Zealand's minimum distance from Australia is a bit more today - some 1,700 km/1,100 miles -, whereas it is now at least 2,500 km (1,550 miles) from Antarctica. The extant species are closely related and thought to be descendants of birds that survived a genetic bottleneck caused by the marine transgression during the Oligocene, when most of New Zealand was under water.〔Cooper A. & Cooper R. (1995). The Oligocene Bottleneck and New Zealand Biota: Genetic Record of a past Environmental Crisis ''Proceedings of the Royal Society of London, Series B.'' 261(1362):293-302.〕 The relationships between the genera and species are poorly understood. The extant genus ''Acanthisitta'' has one species, the rifleman, and the other surviving genus, ''Xenicus'', includes the rock wren and the recently extinct bush wren. Some authorities have retained the Stephens Island wren in ''Xenicus'', as well, but it is often afforded its own monotpic genus, ''Traversia''. The stout-legged wren (genus ''Pachyplichas'') was originally split into two species, but more recent research disputes this. The final genus was ''Dendroscansor'', which had one species, the long-billed wren. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「New Zealand wren」の詳細全文を読む スポンサード リンク
|