In order to assess hybridization of rhesus macaques (Macaca mulatta) from an introduced population with native Japanese macaques (M. fuscata) in the Bousou Peninsula, we examined nine individuals for diagnostic genetic markers of blood proteins (adenosine deaminase and NADH-dependent diaphorase), TSPY (testis-specific protein, Y-encoded) gene and mitochondrial DNA. Two hybrid individuals were confirmed in an introduced group of rhesus macaques inhabiting the southernmost area of the peninsula. Close examination of genotypes revealed that one of the hybrids resulted from crossbreeding in the group for more than one generation. An adult male hybrid was also captured at Sugeno, Ichihara, located in the central hilly zone of the peninsula. Judging from the mtDNA profile, his natal group was not a rhesus but Japanese macaque group. These results suggest reciprocal hybridization between rhesus and Japanese macaques in the peninsula.

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We report here the preliminary results of studies on the distribution and status of five macaque species in Thailand. The latter lies in the center of the Indochinese Peninsula and is an important biogeographical region in SE Asia. We are conducting surveys through out Thailand in the order of questionnaire, census, and capture-and-release fieldwork where feasible. We have determined seven localities of stump-tailed macaques (M. arctoides); 36 localities of long-tailed macaques (M. fascicularis); eight localities of rhesus macaques (M. mulatta); six localities of assamese macaques (M. assamensis); and two localities of pig-tailed macaques (M. nemestrina leonina). Long-tailed and rhesus macaques belong to the same species-group, and are generally distributed allopatrically. The boundary between the two species in NE Thailand appears to lie close to latitude of 16oN. The phenotypic (pelage color and relative tail-length) and genetic characters (mtDNA and TSPY locus) of rhesus macaques resident in the area supposed close to the boundary have been analyzed; the results support the "Hybridization hypothesis" by Fooden ([2000], Fieldiana Zoology 96: 1-180). Troops of long-tailed macaques in Thailand, although their numbers sometimes exceed 1,000 animals, are isolated from other conspecifics. In addition, the genetic disturbance (pollution) introduced by artificial means, e.g., the breeding of released pets and human transfer of macaque troops threatens the innate biodiversity of the Thai macaque species.

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Old World primates have trichromatic vision because they have three types of cone photoreceptors, each of which is maximally sensitive to long (L)-, middle (M)- and short (S)- wavelengths of light. Although a proportion of human males (about 8 % of Caucasians, for example) have X-chromosome-linked color-vision abnormalities, no non-human Old World primates had been found to be color-vision defective to date. However, our molecular genetic analysis showed the existence of male protanopes and female heterozygotes among the long-tailed macaques in Pangandaran National Park, Indonesia (Onishi et al., 1999). The genome of male protanopes contains a single hybrid gene consisting of exons 1 to 4 of the L-photopigment gene and exons 5 and 6 of the M-photopigment gene (L4M5). The absorbance spectrum of L4M5 photopigment was very close to that of M-photopigment. We confirmed the phenotypes of these monkeys by electroretinogram (ERG) flicker photometry (Hanazawa et al., 2001) and by a pattern discrimination task with modified Ishihara pseudo-isochromatic plates (Mikami et al., 2001). The frequency of protanopes in this species was 0.4 %, much lower than in humans. No dichromatic monkeys were found in other macaque species (Onishi et al., 2002). We surveyed long-tailed macaques in Pangandaran National Park, 4 times between 1998 and 2002. This genotype was restricted to 3 neighboring groups among 8 groups in this area. We further surveyed variations of the long- and middle-wavelength-sensitive opsin genes in west and central Jawa, and in southern Thailand. We found another type of hybrid gene in west Jawa and multiple M opsin genes in southern Thailand. In both cases, those genotypes were restricted to each respective area. These results must be helpful to understand the evolution of color vision in primates.

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