Abstract
The Himalaya is one of the youngest and the loftiest mountain chains of the world; it is also referred to as the water tower of Asia. The Himalayan region harbors nearly 10,000 plant species constituting approximately 2.5% of the global angiosperm diversity of which over 4,000 are endemics. The present-day Himalayan flora consists of an admixture of immigrant taxa and diversified species over the last 40 million years. The interesting questions about the Himalayan flora discussed here are: how did the Himalaya achieve high endemic plant diversity starting with immigrant taxa and what were the main drivers of this diversity? This contribution aims to answer these questions and raise some more. We review and analyze existing information from diverse areas of earth and climate sciences, palaeobiology and phytogeography to evolve a bio-chronological record of plant species divergence and evolution in the Himalaya. From the analysis we infer the effects of major environmental upheavals on plant diversity in the region. The understanding developed in the following discussion is based on the idea that Himalaya experienced at least five phases of major geophysical upheavals, namely: (i) mega-collision between India and Eurasian plates, (ii) tectonic uplift in phases and progressive landform elevation, (iii) onset of southwest (SW) Indian monsoon, (iv) spurring of arid conditions in Central Asia, and (v) cyclic phases of cooling and warming in the Quaternary. The geophysical upheavals that were potentially disrupting for the ecosystem stability had a key role in providing impetus for biological diversification. The upheavals produced new geophysical environments, new ecological niches, imposed physical and physiological isolation barriers, acted as natural selection sieves and led to the formation of new species. This contribution aims to develop a comprehensive understanding of the plant biodiversity profile of the Himalaya in the context of complex, interconnected and dynamic relationship between earth system processes, climate and plant diversity.
Highlights
IntroductionHow to cite this article Manish and Pandit (2018), Geophysical upheavals and evolutionary diversification of plant species in the Himalaya
Mountain regions comprise the large majority of the global biodiversity hotspots and it is argued that species diversification is associated with mountain building through changes in landscape and climate followed by formation of varied and heterogeneous habitatsHow to cite this article Manish and Pandit (2018), Geophysical upheavals and evolutionary diversification of plant species in the Himalaya
Strong allopatric divergence was promoted in Hippophae tibetana during the Last Interglacial period (0.13–0.115 million years ago (Mya)) by orogenic processes and climate oscillations during the Quaternary
Summary
How to cite this article Manish and Pandit (2018), Geophysical upheavals and evolutionary diversification of plant species in the Himalaya. For relatively younger mountain systems such as the Himalaya and Mount Kinabalu, their progress as biodiverse landscapes has been shown to be the result of various geophysical upheavals (Pandit, Manish & Koh, 2014; Merckx et al, 2015). The periodic orogenic events led to physiographic and environmental changes (e.g., formation of land bridges, development of monsoon, formation of glaciers and establishment of an elaborate perennial river drainage system) and served as key drivers of the newly evolving ecosystems resulting in geographical isolation of taxa, vicariance, and evolutionary divergence of life forms (Pandit, 2017). The interconnectedness between geophysical and biological components of the Himalayan ecosystems needs to be unraveled to develop insights into understanding of the build-up of its biodiversity
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