New data on the distribution and intraspecific variation of the Millard’s giant rat Dacnomys millardi (Mammalia, Rodentia) from Vietnam

New occurrence records on the rodent species inhabiting Vietnam, based on Joint Russian-Vietnamese Tropical Research and Test Center genetic samples collection

Background

Open access to occurrence records in a standardised format has strong potential applications for many kinds of ecological research and bioresources management, including the assessment of invasion risks, formulation of nature protection, biomedical and management plans in the context of global climate and land-use changes both in the short and long perspective. The accumulation and aggregation of data on the occurrence records of small mammals are relevant for the study of biogeography and for ecological surveys including construction of the spatial distribution and ecological niche modelling of species ' distributions in the context of global climate change. The author has created a dataset of 2408 rodents and tree shrews occurrence records from Vietnam, collected from November 2007 to May 2022. A number of zoologist colleagues also provided genetic samples. A considerable part of these data has been published previously in a number of papers; however, most of these data have yet to be presented. These records cover a significant part of the range of many rodent species in Southeast Asia and provide new data on their distribution. The data were obtained during a number of different field expeditions, where some animals were caught by the author and some were provided by other researchers, resulting in different accuracy levels of geographic coordinates and altitude estimates may range from 10 to 1000 metres in area and from 1 to 100 metres for elevation. A number of samples were genetically examined to avoid inconsistencies with the taxonomic identification. With the help of colleagues, the author created a set of georeferenced occurrence records, adapted to the controlled vocabulary of Darwin Core format datasets, removed duplicates and standardised the format of records using commonly-used unified data structure. This paper presents the resulting dataset of rodents (mostly of Muridae and Sciuridae) along with other small terrestrial species (Scandentia Tupaidae) occurrence records in the territory of Vietnam and Laos.

New information

Much of the distribution data are currently available as open source GBIF databases and potentially may be combined into a united framework for better data resolution. The dataset presented here combines occurrence records of many species over a significant part of their recent natural range, in Vietnam and Laos. The author presents a validated and comprehensive dataset of rodents' occurrence records, based on genetic samples collection compiled during 15 years working in Vietnam (from 2007 to date). Prior to this project, a considerable part of the information about Vietnamese rodents was not available to a wide range of researchers to use these spatial data for analyses by modern methods, for example, for analysis based on geographic information systems (GIS technologies). This dataset now is available for any researchers who use the data format prepared in accordance with Darwin Core standards.For different countries of Southeast Asia and beyond, there are a lot of additional occurrence records for a number of species listed here which may be combined, but a considerable part of them is still scattered over a number of separate literary sources, while another is still presented as maps, field notes and huge amount of museum zoological collections records. The final set was created by a combination of species occurrence records and uniform data structure with verification of the samples' geographic coordinates. Most samples were genetically or/and morphologically verified for correct taxonomical identification, because the most part of the samples presented was carefully investigated by the author himself, both for morphology and genetic attribution. Therefore, the dataset expands the available information on the spatial and temporal distribution of a number of small mammals' species in Southeast Asia. All original notes and geographical localities were carefully checked and any duplicate and erroneous records have been removed from the final dataset.To the date of publication of these data, the GBIF database https://www.gbif.org contained 1408 rodent occurrence records from Vietnam (Fig. 1) along with 240 Scandentia records (Fig. 2), primarily the data on museum materials, including four large collections, such as the Field Museum of Natural History (Zoology) Mammal Collection (646 samples), Australian National Wildlife Collection provider for OZCAM (537), MVZ Mammal Collection Arctos (109), Museum of Comparative Zoology, Harvard University (69) and six other minor collections comprising single specimens.Actually, as for the small terrestrial mammals, Vietnam remains one of the least representative regions in Southeast Asia. Here, we present new data containing 2408 occurrence records, including 2237 rodent records, along with 171 Scandentia ones (Fig. 3). Thus, the data significantly expand our knowledge about actual ranges of a number of species, including rare and endangered ones.