Geissmann, T. 1990: Systematics of crested gibbons (Hylobates concolor group). Abstracts, International Symposium on Primate Conservation in China, pp. 82-83, Kunming Institute of Zoology, Kunming.

Systematics of crested gibbons (Hylobates concolor group)

T. Geissmann

Anthropological Institute, University Zürich-Irchel

Crested gibbons are highly endangered apes; the loss of their original habitat is estimated to be about 75%. The various forms of crested gibbons are mainly distributed in the Indochinese region, but the exact number of taxa as well as their affnities remain unclear. Traditionally regarded as consisting of a single species, Hylobates concolor, this group of gibbons probably contains several species. Only recently, two new black gibbon subspecies have been described from the Province of Yunnan (Ma & Wang, 1986: Zool. Res. 7: 393), and there is some evidence for the existence of additional, previously unrecognized taxa (Geissmann, 1989: Int. J. Primatol. 10: in press). our knowledge of crested gibbon systematics is hence very fragmentary, confused, and sometimes contradictory. This presentation reconstructs the reasons for some of these contradictions, and points out the obstacles that have rendered, and still render, a revision of crested gibbon systematics difficult. Possible solutions to some of these problems are discussed. Only in recent years has the potential of gibbon vocalizations for the analysis of systematic relationships been recognised. A comparative analysis of vocalizations of the various forms within the crested gibbons is in progress by the author. Preliminary results indicate that vocalizations are a powerful tool for the identification of the various taxa of crested gibbons and will provide important information on the number of species included in the concolor group. Recognition of the various crested gibbon taxa is a fundamental precondition both for establishing pure breeding colonies and for investigation of the distribution of the various taxa in future field surveys. This will provide a basis for a comprehensive revision of crested gibbon systematics, and a reconstruction of their phylogenetic radiation. The results will also be of key importance for defining a strategy for urgently-needed conservation efforts.

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