Manish Kumar, Pandit Maharaj K
Department of Environmental Studies, University of Delhi, Delhi, India.
Department of Environmental Studies, Dr. Bhim Rao Ambedkar College, University of Delhi, Delhi, India.
PeerJ. 2018 Nov 7;6:e5919. doi: 10.7717/peerj.5919. eCollection 2018.
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.
喜马拉雅山脉是世界上最年轻、最高耸的山脉之一；它也被称为亚洲水塔。喜马拉雅地区拥有近10000种植物，约占全球被子植物多样性的2.5%，其中4000多种是特有种。当今的喜马拉雅植物群是过去4000万年中移民类群和多样化物种的混合体。这里讨论的关于喜马拉雅植物群的有趣问题是：喜马拉雅山脉是如何从移民类群开始实现高特有植物多样性的，以及这种多样性的主要驱动因素是什么？本论文旨在回答这些问题，并提出更多问题。我们回顾和分析了来自地球与气候科学、古生物学和植物地理学等不同领域的现有信息，以建立喜马拉雅地区植物物种分化和进化的生物年代记录。通过分析，我们推断了主要环境剧变对该地区植物多样性的影响。以下讨论中形成的认识基于这样一种观点，即喜马拉雅山脉经历了至少五个主要地球物理剧变阶段，即：（i）印度板块与欧亚板块的巨型碰撞，（ii）阶段性构造隆升和地形逐渐抬升，（iii）西南季风的开始，（iv）中亚干旱条件的加剧，以及（v）第四纪的冷暖循环阶段。这些可能破坏生态系统稳定性的地球物理剧变在推动生物多样性方面发挥了关键作用。这些剧变产生了新的地球物理环境、新的生态位，形成了物理和生理隔离屏障，充当了自然选择筛子，并导致了新物种的形成。本论文旨在在地球系统过程、气候和植物多样性之间复杂、相互关联和动态的关系背景下，全面了解喜马拉雅山脉的植物生物多样性概况。
