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.
As it will be seen in the following chapter the available zoogeographical data support this scheme. Having analysed the species composition of the rodent fauna of Vietnam (see Table 1) its most characteristic feature becomes clear: a mixing of the temperate and subtropical elements from the northern fauna with the tropical ones from the southern faunas. Attention must be paid to the feet that for some forms of the temperate zone ( Eothenomys, Micro- mys, Niviventer confucianus) and those of the subtropical zone ( Rattus flavipectus , Rattus nitidus , Callosciurus erythraeus) North Vietnam represents the southern limit of their ranges; and on the contrary for some tropical forms ( Callosciurus flavimanus, Rattus exulans , Hylopetes spadiceus , Menetes bredmorei etc. ) it is the northern limit of their ranges. On the basis of the data from a number of authors we have to point out the following general zoogeographical characteristics of the rodent fauna of Vietnam. 1. Cosmopolite species: to this group belong only two species (3. 1 %). The areal of the species Mus musculus includes five geographical regions (Ethiopian, Indo-Chinese, Holarctis, Nearctis and Australia). Rattus norvegicu s - the other species of this kind - originates according to a number of authors from North China. The latter species has been distributed by different kinds of transport means over the whole world up to date. 2. Almost all of the rodent species of Vietnam belong to those of the indo-Chinese fauna - 58 species (92%); these species determine the general feature of the rodent fauna of our country. 3. 13 species (20.8%) are common with those of the Indian fauna, 30 species (47.2 %) represent common elements with the Sunda fauna, 14 species (22.2%) are common faunal elements with the Palaearctic fauna and only three species are shared by the Vietnamese fauna with that of Wallacian. And at last, there are species which can be found only in this district - these are endemic species or species discovered as new for science ( Rattus os- goodi). The above-reported data used for the zoogeographical analysis were suitable to draw the following conclusions. The composition of the rodent fauna of Vietnam is characterized by the fact that in the north it has been mixed with Palearctic elements, in the south with those of the Indo-Malayan fauna. The mixed character of the fauna agrees to the geographical situation of our country. But the Vietnamese rodent fauna is strongly connected with the districts of the Indo-Malayan region further in the south. Smaller is the number of the faunal elements being common with the Palearctic (22.2%) and Indian ones (20.8%), especially small is the number of species shared by the Wallacian subregion (4. 7%). Not one species of the rodent fauna of Vietnam occurs in the Ethiopian or the Australian regions. It seems reasonable to suppose that in the forming of the rodent fauna of Vietnam elements of the Oriental realm had a determining role. In analysing the fauna of Vietnam we have to rely first of all on the characteristic features revealed by the present distribution of different representatives of the seven rodentfamilies inhabiting this country. The simplest structure is represented by the families Cri- cetidae and Arvicolidae both of them have only one typical species), and the range inhabited by them to the ridge Phan Si Pan. For the species of the other families two variants exist. There are species whose range lies in the southern part of Vietnam, e.g. Callosciurus flavimanus , Callosciurus notatus, Hylopetes lepidus, Hylopetes spadiceus , Sundasciurus hippurus , etc. and there are species having their ranges in the northern parts of Vietnam, e.g. Callosciurus erythraeus , Callo- sciurus pygerythrus , Dremomys pernyi etc. The range of many other species occupies the whole territory of the country (Table 1). We should bear in mind that all of the last-mentioned species are typical for the Oriental realm. The number of endemic species is very small. Only three species have been recorded by us (Rattus germaini, Rattus osgoodi , Maxomy s moi) , which are found only in mountainous localities of difficult access. It can be stated that inspite of the heterogeneous character of the rodent fauna of Vietnam preponderate in it the elements of the Oriental realm. A group of "southern" species originating from the Malayan subregion can be found in the southern part of Vietnam, whereas the group of "northern" species of North-Chinese and Burmese-Indian origin inhabits the Analysis of the rodent fauna of Vietnam
