The recent fossil turtle record of the central plain of Thailand revealslocal extinctions

The recent fossil turtle record of the central plain of Thailand revealslocal extinctions


ไทย :

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English :

With more than 50 extant turtle species, Southeast Asia is currently a hotspot of turtle biodiversity.However, the distribution areas of most species are decreasing as a consequence of human activities.The causes of this decline are multiple: habitat and natural resources destruction, introduction of inva-sive species, hunting, etc. Historical data are however still lacking for a detailed understanding of thatregional trend as well as for forecasting its evolution in the future. Indeed, while oral testimonies andtext data can provide a rather good appreciation of the decline of biodiversity over the last few decades;nothing is known about the dynamic of turtle biodiversity over the Holocene. This lack of data is espe-cially damaging in area where human activities are interacting for a long time with the wild fauna,as the central plain of Thailand, which is now dominated by agricultural landscape. In order to solvethese issues, we investigated five Holocene localities in Thai central plain which provided assemblagesof turtle remains ranging from Neolithic to Dvaravati periods (4000 to 1000 BP). The studied archae-ological assemblages showed a very high species richness. Species such as Malayemys macrocephala,Cuora amboinensis, Heosemys annandalii, Heosemys grandis, Siebenrockiella crassicolis, Amyda ornata wereamong the most abundant. We also found several plates and a cranial material belonging to a speciesof the genus Batagur and tortoise remains including Indotestudo elongata and a few plates belonging tothe genus Geochelone. The Batagur and Geochelone genera are absent from living turtle assemblages inthe central plain but are present in Myanmar, Cambodia, Indonesia or Southern Thailand for Batagurand far in the West for Geochelone (Myanmar) respectively. Batagur is usually found in coastal areasand its disappearance from central plain is interpreted as resulting from the destruction of a fragilehabitat and possibly from the rapid geomorphological evolution of the Chao-Phraya deltaic plain, the disappearance of tortoises could result from deforestation. Cutting traces showed that most turtles wereused as food resources at these times, suggesting that turtle hunting was a common practise. Furthermore,occurrence of holes in the margin of the carapace of specimens from Kheed Khin (Saraburi Province) andPromthin Tai (Lopburi Province) suggests that turtles were sometimes kept captive alive or transported.This study shows that investigation of recent fossil localities allows for a better understanding of the roleof past human populations in the alteration of the biodiversity through time, and for a more accurateestimation of the rates of species extinction.