Poster Presentation
JayarajVijaya Kumaran1,2,*, Ahmad Sofiman Othman2, ShahrulAnuarMohd Sah2, Seri Intan Mokhtar3
The timeline of evolution and diversification of treeshrews in the Indo-Malayan region
1Faculty of Earth Science, Universiti Malaysia Kelantan
2School of Biological Science, UniversitiSains Malaysia
3Faculty of Agro Based Industry, Universiti Malaysia Kelantan
Abstract:- Fossil records are integral part of many evolutionary studies nowadays as these records combined with genetic data can be used to estimate speciation events. The timeline of diversification of Scandentia previously determined by Roberts et al. (2011) indicated that the diversification of tree shrews occurred during the Miocene period and continued right up to the late Pliocene period. However the current diversity of tree shrews may be underestimated, as widespread species such as T. glis, T. belangeri, T. minor and A. elliotimay probably have divergent populations that have yet to be discovered. Here we present a re-analysis of evolutionary time line for tree shrews (Scandentia), a group of mammals endemic to the Indo-Malayan region. 12S gene sequences of tree shrews and other selected taxa of mammals were downloaded from NCBI (Genebank) and an additional 2 species of tree shrews newly discovered in Peninsular Malaysia was included in a Bayesian Markov Chain Monte Carlo (MCMC) analysis implemented in BEASTv2. A total of 5 fossil records 2 tree shrews, primates and ancestral clade of Euarchontawas used as the calibration point for branch splitting events. The first calibration was based on Tupaiamiocena at 18 Mya (Mein and Ginsburg 1997), which was the oldest known Tupaia and the fossil record for Eodendrogale (from the Middle Eocene, 37.2mya; Tong 1988) was then used for calibration for the Most Recent Common Ancestor (MRCA) of all Scandentia. Primate fossil records were also used as additional calibration points with reference to Timetree of Life database (Hedges et al. 2006).Our analysis indicates that there were 2 major speciation events that happened during the Miocene and Pliocene period that shaped the diversity of tree shrews known today. Our analysis also indicates there may probably be more species to be discovered given the possibility that the period of Pleistocene may also play a role in the diversification of tree shrews in the Indo-Malayan region. The separation of the additional T. glisphylogroup (provisionally named as T. glisphylogroup Sumatra) from the T. glisphylogroupsof Peninsular Malaysia is estimated to be 3.06mya in the Pliocene epoch. If the "out of Borneo theory" (Roberts et al. 2011) was invoked, the route of colonization of the common ancestor of T. glis and T. belangeri to the mainland of Peninsular Malaysia would be from Sumatra to Peninsular Malaysia up to southern Thailand. The colonization of T. glis and T. javanica in to Java from Sumatra would have happened after 2.4 mya as there was no mammals in Java prior to that period. This may likely happened due to secondary contact i.e connection of land bridges between these two major islands (Meijard 2004). The results highlights the importance accurate dating of fossil records in determining the species splitting events in the evolution of mammals.
Keywords: Fossil records, Scandentia, genetic analysis
References
Hedges, S. B., & Kumar, S. (eds.). (2009).TheTimetree Of Life. Oxford University Press.
Meijaard, E., 2004. Solving mammalian riddles: a reconstruction of the tertiary and quaternary distribution of mammals and their palaeoenvironments in island South-East Asia. School of Archaeology And Anthropology, The Australian National University, Canberra, Australia, p. 349.
Mein, P., & Ginsburg, L. (1997). Les mammifčres du gisementmiocčneinférieur de li mae long, thaïlande: systématique, biostratigraphie et paléoenvironnement.Geodiversitas,19(4), 783-844.
Roberts, T. E., Lanier, H. C., Sargis, E. J., & Olson, l. E. (2011). Molecular phylogeny of treeshrews (Mammalia: Scandentia) and the timescale of diversification in Southeast Asia.Molecular Phylogeneticsand Evolution,60(3), 358-372.
Tong, Y. (1988).Fossil tree shrews from the Eocene Hetaoyuan Formation of Xichuan, Henan.Vertebrata palasiatica,26, 214-220.