Geographical Variation within the Species Ratufa bicolor (Sparrman, 1778) Inferred from External and Cranial Morphology (Sciuridae: Ratufinae) in Thailand

Ngagyel Tenzin; Sara Bumrungsri; Chutamus Satasook

Authors

Ngagyel Tenzin Department of Biology, Faculty of Science, Prince of Songkhla University, Hat Yai 90112 Thailand
Sara Bumrungsri Department of Biology, Faculty of Science, Prince of Songkhla University, Hat Yai 90112 Thailand
Chutamus Satasook Department of Biology, Faculty of Science, Prince of Songkhla University, Hat Yai 90112 Thailand; Princess Maha Chakri Sirindhorn Natural History Museum, Faculty of Science, Prince of Songkhla University, Hat Yai 90112 Thailand

Keywords:

Bergmann’s rule, delimitation, Isthmus of Kra, sexual dimorphism

Abstract

The giant black squirrel, Ratufa bicolor is distributed widely from the south to the north of Thailand. It is easily distinguished from other squirrels owing to its larger size. In this study, the northern population was delimited above the Isthmus of Kra and the southern population below the Isthmus of Kra following the biogeographic transition zone of Hughes et al., 2011. Four external and twenty-four cranial characteristics were studied to determine the geographical variation of this species. Mean measurements suggest that the northern population is larger. In addition, eleven skull characteristics show significant differences between the northern and southern populations. Principal component analysis also identifies two distinct populations.

References

Barnett, R. J. 1977. Bergmann's Rule and Variation in Structures Related to Feeding in the Gray Squirrel. Society for the Study of Evolution. 31(3): 538-545.

Chaimanee, Y. 1998. Plio-Pleistocene rodents of Thailand. Bio-diversity Re-search and Training Program, National Center for Genetic Engineering and Biotechnology (BIOTEC), Cham-long Phengklai, Thailand. 303 pp.

Corbet, G. B. and J. E. Hill. 1992. The mammals of the Indo-malayan region; Systematic review. Oxford University Press, New York. 488 pp.

Francis, M. C. 2008. A field guide to the mammals of Thailand and South-east Asia. Asia Books Co. Ltd, Bangkok. 392 pp.

Gorrell, J. C., S. Boutin, S. Raveh, P. Neuhaus, S. D. CÔTÉ and D. W. Coltman. 2012. Sexing the Sciuridae: a simple and accurate set of molecular methods to determine sex in tree squirrels, ground squirrels and marmots. Molecular Ecology Resources. 12(5): 806-809.

Hayashida, A., H. Endo, M. Sasaki, T. Oshida, J. Kimura, S. Waeng-sothorn, N. Kitamura and J. Yamada. 2006. Geographical Variation in Skull Morphology of Gray-bellied Squirrel Callosciurus caniceps. Journal of Veterinary Medical Science. 69(2): 149-157.

Hughes, A. C., C. Satasook, P. J. J. Bates, S. Bumrungsri and G. Jones. 2011. Explaining the causes of the zoogeographic transition around the Isthmus of Kra: Using bats as a case study. Journal of Biogeography. 38(12): 2362-2372.

Hughes, J. B., P. D. Round and D. S. Woodruff. 2003. The Indo-chinese-Sundaic faunal transition at the Isthmus of Kra: an analysis of resident forest bird species distribution. Journal of Biogeography. 30: 569-580.

IUCN. 2012. Red List of Threatened Species, Vol. 2012.

Lekagul, B. and J. A. McNeely. (Eds.). 1988. Mammals of Thailand. Saha Karn Bhaet Co., Bangrak, Bangkok. 758 pp.

Lunde, T. and N. T. Son. 2001. An Identification guide to the rodents of Vietnam. American Museum of Natural History, New York. 88 pp.

MacKinnon, S. K. 1978. Stratification and feeding differences among Malayan squirrels. Malayan Nature Journal. 30(3/4): 330-608.

Mitchell, R. 1979. The Sciurid rodents of Nepal. Journal of Asia Ecology. 1: 21-28.

Moore, J. C. and G. H. H. 1965. A study of diurnal squirrels, Sciurinae, of the Indian and Indo-Chinese subregions. Natural History Museum Press, Chicago. 351 pp.

Roth, V. L. 1996. Cranial Integration in the Sciuridae. American Zoologist. 36(1): 14-23.

Thorington, Jr., J. L. Koprowski, M. A. Steele and J. F. Whatton. 2012. Squirrels of the world. John Hopkins University Press, Baltimore. 459 pp.

Thorington, R. W. and K. Ferrell. 2006. Squirrels animal answer guide. Johns Hopkins University Press, Baltimore. 195 pp.

Timmins, J. R. and J. W. Duckworth. 2008. Diurnal squirrels (Mammalia Rodentia Sciuridae) in Lao PDR: Distribution, status and conservation. Tropical Zoology. (21): 11-56.

Wilson, D. E., and D. M. Reeder. 2005. The mammals Species of the World. The Johns Hopkins University Press, Baltimore. 2142 pp.