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SPECIES VARIATION - Editorial Comment

Editorial Comment

(Editorial Overview Text Replicated on Overall Species page - Pan paniscus - Bonobo)
  • Bonobos are monotypic, with no subspecies. Now accepted as Pan paniscus, a separate species within the genus Pan, previously they had been considered only a subspecies of Pan troglodytes. However, it has also been suggested that differences are such that they should be placed in their own genus.

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Intraspecific Variation

Source Information

Monotypic.
  • Pygmy chimpanzees were first described as Pan satyrus paniscus in 1928 by Dr Ernest Schwarz, based on skulls and skin. (B596.1.w1)
  • Elevation to full species status was first proposed by Coolidge in 1933 (J569.18.w1). 
  • A distribution map published in 1944 showed clearly that Pan paniscus and Pan troglodytes were allopatric. (B596.1.w1)
  • A comparative study of blood group serology concluded that not only were Pan paniscus and Pan troglodytes separate species, but that they "are even as distant from P. troglodytes as to be placed in a separate genus." (B596.2.w2)
  • Based on mitochondrial DNA and serum electrophoretic data, Pan paniscus and Pan troglodytes diverged about 1.5 MYA (million years ago), in the early Pleistocene period. (B596.3.w3)
  • Bonobos have previously been considered as a subspecies of chimpanzee: Pan trogodytes paniscus. The two species are thought to have diverged about 2.5 million years ago. (B147)
  • Acceptance of bonobos as a separate species rather than a subspecies within Pan troglodytes has not been universal, with publications in the late 1970s/early 1980s arguing for only a subspecific designation. (J569.51.w1, B596.8.w8)
  • In 1925 a young chimpanzee from the Congo, named "Prince Chim", was described as being of "an unusual type which rarely is seen in America", with a black face, small ears, "rather conspicuous" nose and fine hair: he was, although unrecognised at the time, a bonobo. The author noted the difference in Prince Chim's personality compared with Panzee, another young chimpanzee. Prince Chim was described as follows: "I have never met an animal the equal of Prince Chim in approach to physical perfection, alertness, adaptability and agreeableness of disposition." He was "even-tempered and good-natured, always ready for a romp", seldom showing resentment and never showing jealousy, and he was considerably less timid of new experiences than Panzee. Additionally he was noted to have "remarkable alertness and quickness to learn." (B597.13.w13)
  • Investigation of genetic diversity in bonobos, using DNA from faecal samples collected from 150 individuals of an estimated eight wild communities across the bonobos' geographical range, showed little geographical patterning of variation. (P119.2003.w17)
  • Note: It has been suggested (2001) that the name "marungensis" was first used for what are now considered to be bonobos, predates that of "paniscus" and should thus properly be used to denote the bonobo as Pan marungensis, but that this would produce considerable confusion, therefore should not be used. (J576.42.w2) However, more recent work (accepted by the author of the 2001 paper) has established marungensis as belonging to Pan troglodytes, either as part of Pan troglodytes schweinfurthii or (suggested by the author) as a fifth subspecies Pan troglodytes marungensis, for the most south-easterly chimpanzees. (J587.17.w1)
  • A study using the mitochondrial DNA control region with construction of phylogenetic trees based on both the neighbour-joining and maximum-likelihood methods, two major clades, A and B) of bonono genotypes were detected. In the Central and Southern regions, both haplotypes were found approximately evenly; in the north and northeast, haplotype A was more common and in the East, only clade B was found. Based on both nucleotide and haplotype diversity, the level of diversity in bonobos was found to be intermediate between that of humans and chimpanzees, and similar to that of a single Pan troglodytes subspecies. Genetic distances between regions showed significant correlation with geographical distance measured going around rivers and not with straight-line distance between populations, indicating that major rivers have acted as effective barriers. (J335.13.w1)
Hybridization
  • Hybridization with Pan troglodytes has occurred in captivity between a male Pan paniscus and two female Pan troglodytes. (P119.2003.w13)
  • Five hybrids were recorded between a male bonobo and female chimpanzees. Two of these were aborted, as an embryo of about 2-3 months, and as a fetus of about six months (this abortion aparently due to stress during a storm). Two offspring were live born to one female and one to another female. Compared to common chimpanzees, the hybrid infants were noted to have smaller, darker ears, a darker, less prognathic face, pink lips, marked whiskers, larger and more ventrally-orientated genitalia in the two females. By one year of age the male showed a wider chest than not=rmal for Pan paniscus and spotted skin pigmentation on the inner thighs. No webbing between the second and thid toe on any of the infants. Preliminary voice analysis idicated characteristics of both species. Compared to common chimpanzees, the yearling male was noted to have less aggressive behaviour and show a marked preference for water, as well as often walking bipedally. (J187.56.w1)

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Authors & Referees

Authors

Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)

Referee

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