Geissmann, T. (2010). Taxonomy and historical distribution of the crested gibbons (genus Nomascus). Primate Research (Primate Society of Japan) 26, Supplement (September 2010): 88 (Abstract only).
Anthropological Institute and Museum, University of Zürich, Switzerland
The crested gibbons have traditionally been regarded as a single species, Hylobates concolor, containing 6 subspecies (concolor, hainanus, lu, leucogenys, siki, gabriellae). More recent studies using vocal data, morphological data, and DNA sequences suggest that these gibbons should be recognized as a distinct genus (i.e. Nomascus) consisting of several species. These include: (1) black crested gibbon (Nomascus concolor) from China, Laos, and Vietnam, (2) cao-vit crested gibbon (Nomascus nasutus) from China and Vietnam, (3) Hainan crested gibbon (Nomascus hainanus) from China, (4) northern white-cheeked crested gibbon (Nomascus leucogenys) from China, Laos, and Vietnam, (5) southern white-cheeked crested gibbon (Nomascus siki) from Laos and Vietnam, and (6) yellow-cheeked crested gibbon (Nomascus gabriellae) from Cambodia, Laos, and Vietnam. Vocal data and DNA sequences produce virtually identical phylogenies suggesting that hainanus and nasutus represent the most basal clade of the genus, followed by concolor, then by gabriellae, while siki and leucogenys are the last species to diverge. Although the male phenotypes of siki and leucogneys are clearly distinct, preliminary vocal and molecular data suggest a close relationship. The identity of the crested gibbons occurring in a large area encompassing parts of central Vietnam, southern Laos and northeastern Cambodia is uncertain, as these differ in their song from both gabriellae and siki, but phenotypically resemble gabriellae. This may be a new subspecies of N. gabriellae. Habitat destruction and hunting resulted in a dramatic reduction of the distribution area of crested gibbons China, but also affect species in other countries, for instance N. leucogenys in Vietnam.
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