Spatiotemporal maintenance of flora in the Himalaya biodiversity hotspot: Current knowledge and future perspectives.

Moses C Wambulwa,Jie Liu,Jim Provan,Lian‐Ming Gao,Ya‐Huang Luo,Hong Wang,Guang‐Fu Zhu,De‐Zhu Li,Zeng‐Yuan Wu,Robert A Spicer,Wan‐Ting Wang,Richard Milne

doi:10.1002/ece3.7906

Abstract

Mountain ecosystems support a significant one‐third of all terrestrial biodiversity, but our understanding of the spatiotemporal maintenance of this high biodiversity remains poor, or at best controversial. The Himalaya hosts a complex mountain ecosystem with high topographic and climatic heterogeneity and harbors one of the world's richest floras. The high species endemism, together with increasing anthropogenic threats, has qualified the Himalaya as one of the most significant global biodiversity hotspots. The topographic and climatic complexity of the Himalaya makes it an ideal natural laboratory for studying the mechanisms of floral exchange, diversification, and spatiotemporal distributions. Here, we review literature pertaining to the Himalaya in order to generate a concise synthesis of the origin, distribution, and climate change responses of the Himalayan flora. We found that the Himalaya supports a rich biodiversity and that the Hengduan Mountains supplied the majority of the Himalayan floral elements, which subsequently diversified from the late Miocene onward, to create today's relatively high endemicity in the Himalaya. Further, we uncover links between this Miocene diversification and the joint effect of geological and climatic upheavals in the Himalaya. There is marked variance regarding species dispersal, elevational gradients, and impact of climate change among plant species in the Himalaya, and our review highlights some of the general trends and recent advances on these aspects. Finally, we provide some recommendations for conservation planning and future research. Our work could be useful in guiding future research in this important ecosystem and will also provide new insights into the maintenance mechanisms underpinning other mountain systems.

Highlights

Mountain ecosystems are important as biodiversity reservoirs (Myers et al, 2000), and as sources of raw materials and for their associated sociocultural value (Stepp et al, 2005)
Where the elevational gradient is strong, drastic altitudinal climate variation over very short distances may create different environmental niches very close together, such juxtapositions can result from simple geometric constraints on species distribution boundaries without the action of any environmental gradients (Brehm et al, 2007; Colwell et al, 2004), potentially driving divergence and speciation (Doebeli & Dieckmann, 2003; Funk et al, 2016)
In spite of the major role played by immigration in the assembly of the Himalayan flora, numerous studies have argued in favor of in situ speciation and diversification, which were triggered by the orogeny and the subsequent climatic changes in the Himalaya and its surrounds (e.g., Bai et al, 2015; Rana, Luo, et al, 2019; Ren et al, 2017; Xie et al, 2014; Xing & Ree, 2017; Zhao et al, 2016), and which could offer a convincing explanation for the high endemism in the Himalaya

Summary

Introduction

Mountain ecosystems are important as biodiversity reservoirs (Myers et al, 2000), and as sources of raw materials and for their associated sociocultural value (Stepp et al, 2005). KEYWORDS biodiversity hotspot, climate change, elevational gradient, Himalayan flora, mountain ecosystem, spatiotemporal diversification

Results

Conclusion