O. Gy. Dely szerk.: Vertebrata Hungarica 23. (Budapest, 1989)
Cao, van Sung: On the problem of zoogeographical division of the rodent fauna of Vietnam (Mammalia, Rodentia) 57-66. o.
well as five subspecies of the yellow-handed Squirrel from the southern part of Vietnam ( Cal losciurus flavimanus piratus, C. f. fanrangis, C. f. contumax, C. f. dactylis , C. f. grisei- manu s) . In the Quaternary on the territory of Vietnam there was an immense geological activity (tectonic as well as volcanic). As a result of such geological movements before 600, 000 years the basalt plateau of Tay nguyen was lifted, too. And even here we can find a very characteristic vegetation (Dipterocarpu s forests, rich grassy fields). This peculiar vegetation serves as habitat for a number of typical rodent species. An other important factor is that the thawing of the ice' following each glacials raised the sea-level by 200 m. This allowed the parting of the Sunda islands from the Indo-Chinese mainland. The faunal elements originating from the Sunda islands and being present now in the rodent fauna of Vietnam prove the former connection (Hylopetes spadiceus, Menetes berdmorei, Hystrix brachyurus , Callosciurus notatus , Callosciurus nigrovittatus, Sundasciurus hippuru s, etc. ). The distribution of the rodent fauna of Vietnam depends on the climate and geographical relief conditions. Species originating from Palearctic have their ranges at present mainly on the tops of massives and high mountains ( Eothenomys melanogaster , Micromys minutus) . Some other species as Menetes berdmorei, Hylopetes spadiceus , Callosciurus finlaysoni etc. are inhabitating the xerophilic deciduous forests of Vietnam which are very similar to their original range located in the Sunda islands. Thus, the rodent fauna of Vietnam is composed of elements, which are different both according to their ecological type and to their origin. The zoogeographical division of Vietnam seems to meet - in its main features - the present life conditions of the country. Each province and district has its own particular and special fauna. But the aim of zoogeography is not only to establish the elements of which the fauna consist of a given territory, but also to elucidate its genesis. In the recent fauna of Vietnam a number of ancient elements of the Oriental realm is represented, therefore the ancestral character of the endemic fauna is without doubt. The mixed character of the rodent fauna of Vietnam is closely connected with the ecological plasticity of the elements and their adaptability to the various life conditions of Vietnam. From the fact that the rodent species of northern origin are restricted to the northern part of Vietnem, whereas those of southern origin to the southern parts of the country, it can be concluded that in the past the expansion of northern elements to the south was prevented by natural barriers. On the other hand, it can be explained by these barriers why are living certain species on localities situated very far from each other. Callosciurus finlaysoni can be found on the island Phu quoc and in Sa thay in district Gia Lai-Kon Turn. The fossilic fieldvole (Microtus ) species excavated in the northern parts of Vietnam reveal the fact that all of these species reached in the geological past our country, but they became extinct, because life conditions were not suitable for their survival. REFERENCES BOURRET, R. (1942): La faune de l' Indochinoise. Les Gibbons. - Hanoi. CAO van Sung (1978): Rodent fauna of Vietnam. - Sei. Report. Biology, Hanoi: 131-139. CHASEN, F.N. (1940): A handlist of Malaysian Mammals. - Bull. Raffles Mus. No. 15. DAO van Tien (1978): Experience of zoogeographical zonation of Vietnam. - Zool. J. 57 (4): 582-586. DAO et al. (1970): Results of zoo-parasitological survey of North Vietnam in 1962-1966. Geo-Biological J. 8 (1-2): 4-32. ELLERMAN, J.R. et MORRISON-SCOTT, T.C.S, (1951): Checklist of Palearctic and Indian Mammals. - Brit. Mus. Nat. Hist. London: 456-670. JACCARD, L. (1902): Lois de distribution florale dans la zone alpine. - Bull. Soc. Vaudoise Sc. Nat. 5: 38. HONACKI, H.E. et al. (ed.) (1982): Mammals species of world. - Lawrence (Kans.): 694 pp. LEAKAGUL, B. et McNEELY, J.A. (1977): Mammals of Thailand. - Bangkok. MAI DINH YEN (1963): On the composition, origin and distribution of fish population in Red River. - Geobiological J. 2 (1): 34-39.
