Plant Diversity ›› 2023, Vol. 45 ›› Issue (03): 243-264.DOI: 10.1016/j.pld.2022.12.003

• Review • Previous Articles     Next Articles

Siwalik plant megafossil diversity in the Eastern Himalayas:A review

Mahasin Ali Khana, Sumana Mahatoa, Robert A. Spicerb,c, Teresa E.V. Spicerb, Ashif Alia, Taposhi Hazraa, Subir Berad   

  1. a. Palaeobotany and Palynology Laboratory, Department of Botany, Sidho-Kanho-Birsha University, Ranchi Road, Purulia 723104, India;
    b. CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, PR China;
    c. School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, MK7 6AA, UK;
    d. Centre of Advanced Study, Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata 700019, India
  • Received:2022-07-31 Revised:2022-12-05 Published:2023-07-06
  • Contact: Mahasin Ali Khan,
  • Supported by:
    MK and SM gratefully acknowledge the Department of Botany, Sidho-Kanho-Birsha University for providing infrastructural facilities to accomplish this work. SB acknowledges the Centre of Advanced Study (Phase-VII), the Department of Botany, the University of Calcutta for providing necessary facilities. We also thank Prof. Paul Valdes, Bristol University, U.K., for providing the modern WorldClim2 climate data for the fossil localities. RAS and TEVS were supported by NERC/NSFC BETR Project NE/P013805/1.

Abstract: The Eastern Himalayas are renowned for their high plant diversity. To understand how this modern botanical richness formed, it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan Siwalik succession (middle Miocene-early Pleistocene). Here, we present a summary of plant diversity records that document Neogene floristic and climate changes. We do this by compiling published records of megafossil plant remains, because these offer better spatial and temporal resolution than do palynological records. Analyses of the Siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time. This qualitative interpretation is also corroborated by published CLAMP (Climate Leaf Analysis Multivariate Program) analyses. Here, we also reconstruct the climate by applying a new common proxy WorldClim2 calibration. This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations. An analysis of the Siwalik floras indicates that there was a gradual change in floral composition. The lower Siwalik assemblages provide evidence of a predominance of evergreen elements. An increase in deciduous elements in the floral composition is noticed towards the close of the middle Siwalik and the beginning of the upper Siwalik formation. This change reflects a climatic difference between Miocene and Plio-Pleistocene times. This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic.

Key words: Megafossils, Siwalik, Miocene-Pleistocene, Palaeovegetation, Palaeoenvironment, Eastern Himalayas