Uplift history and biological evolution of the Himalaya (I)

The Himalaya, a majestic mountain range often referred to as the “Roof of the World,” is distinguished by exceptional environmental heterogeneity, rich biodiversity, and high taxonomic endemism (Kitamura, 1963; Tabata, 1988; Sun, 2002). It serves as a natural “laboratory” for studying the formation, evolution, and patterns of biodiversity (Wen et al., 2014). The complex uplift history of the Himalaya has profoundly influenced biodiversity patterns across Asia and the globe, primarily through how it modifies the Asian monsoon system. In this special issue, we present 12 papers focusing on the Himalaya and surrounding regions, addressing topics such as paleoaltitude and paleovegetation reconstruction, biogeographic regionalization, floristic classification and history, and biodiversity conservation. These contributions aim to provide fresh perspectives and valuable insights into these critical topics. Geographically and ecologically, the Himalaya is closely linked to neighboring highland regions, including the Tibetan Plateau and the Hengduan Mountains. The Tibetan Plateau, the world′s largest and highest plateau, lies to the north of the Himalaya and had a complex tectonic development. To the southeast, and in contrast to the relatively flat plateau the Hengduan Mountains are characterized by dramatic high relief topography and exceptional biodiversity, featuring the highest vascular plant species richness and endemism, along with strong floristic and faunal connections to the Himalaya. Collectively, these regions form a distinct high-altitude system that has significantly shaped biodiversity patterns and climatic dynamics across Asia. This interconnectedness extends to broader concepts such as the Qinghai–Tibet Plateau (QTP), Pan-Tibetan Highlands, and Pan-Himalaya. The QTP, a widely recognized term, generally includes the plateau itself (sometimes referred to as the Qinghai-Tibet Plateau s.s.), along with the Himalaya and the Hengduan Mountains (Liu et al., 2021; Mao et al., 2021). Unfortunately, this combining of areas with very different geomorphological characteristics complicates understanding speciation processes and the origins of biodiversity. The inclusion of the Mountains of Central Asia to the northwest forms the “Pan-Tibetan Highlands” (Liu et al., 2022), but these authors point out the importance of treating regions with different geomorphological characteristics as separate entities for biodiversity studies. In contrast, the Pan-Himalaya is defined by floristic boundaries, encompassing the high relief Himalaya, the Hengduan Mountains, and adjacent regions with shared floristic characteristics (Wang & Hong, 2022). Regardless of the specific definitions or boundaries, the Himalaya, as an independent tectonic unit, undoubtedly exerts a profound influence on Asian biodiversity and climate change. Yang et al. (2025) reviewed the history of plant diversity surveys and monographic studies in the Pan-Himalaya region, highlighting the progress of the ongoing international Flora of Pan-Himalaya (FPH) project. They also emphasized the importance of prioritizing northern Myanmar and the Yarlung Zang–Brahmaputra for further botanic surveys. Liu et al. (2025) proposed a phylogenetic regionalization of the Pan-Himalayan vascular flora, dividing it into 15 zones grouped into five subregions and three main regions: West Himalayan, Southeast Himalayan, and Northeast Himalayan, based on comprehensive species distribution data and a species-level phylogenetic tree. The characteristics of these subregions and their floristic connections underscore the cohesion of the Pan-Himalaya as a unified floristic region. The Himalaya, formed by the collision of the Indian and Eurasian plates, represents a major Cenozoic geological event that profoundly shaped Asia's topography and climate. The timing and processes of its uplift, along with the formation of adjacent regions such as the Tibetan Plateau and the Hengduan Mountains, remain complex and an active focus for scientific inquiry. Two key debate aspects include: (i) whether the Tibetan Plateau had reached near-modern elevations by the Eocene (Rowley & Currie, 2006; Renner, 2016); and (ii) the tendency to treat the Tibetan region as a single entity (see critique in Spicer et al., 2021), sometimes using the Himalaya to represent the entire region. This oversimplification overlooks the fact that the plateau consists of several distinct tectonic terranes and the Himalayan orogenic belt, each with its own unique geological history. Although evidence from geology, paleontology, and modern biology have often conflicted in the past, recent studies have gradually led to an emerging consensus, often due to better dating of fossil assemblages and improved paleoaltimetric techniques. The uplift of the Himalaya began with the India–Asia continental collision around 65–60 Ma. During the Eocene, the Himalaya and much of the Tibetan Plateau had not yet reached their current elevations of ~4–5 km. Instead, the central plateau featured a low-altitude, east–west-oriented Paleogene Central Tibetan Valley, which served as a cradle and conduit for thermophilic biota (Su et al., 2020). The subsequent rise of eastern Tibetan Plateau intensified regional rainfall and erosion. The Himalayan orogenic belt surpassed 4000 m in elevation, ca. 15 Ma, followed by gradual and continuous uplift. This process enhanced topographic relief and drove biodiversification (Spicer et al., 2003; Ding et al., 2020; Spicer et al., 2025). Regional uplift also significantly influenced vegetation and plant diversity in eastern Asia by shaping the monsoon system (An et al., 2001; Li et al., 2021; Zhang et al., 2024), with modern-like Asian monsoons emerging only after the plateau's substantial formation during the Miocene (Spicer et al., 2025). Lai et al. (2025) proposed a novel method to calibrate paleoelevation by comparing fossil and extant plant communities in the Himalaya and the Tibetan Plateau, detailing the uplift processes of each terrane. When using the timing of Himalayan uplift to calibrate the divergence times of taxa, it is crucial to account for the distinct uplift histories of different tectonic units rather than treating the region as uniform entity. Zhang et al. (2025b) and Xie et al. (2025a) used phytoliths and pollen, respectively within the late Oligocene–Early Miocene sedimentary section of the Lunpola Basin, central Tibetan Plateau, to reconstruct the vegetation. Both proxies indicate that the vegetation in the central Tibetan region primarily comprised a mixed deciduous broad-leaved and coniferous forest surrounding the Lunpola paleolake during the latest Oligocene to Early Miocene. This vegetation pattern was shaped by the rise of the central Tibetan region, the retreat of the Tethys Ocean, and the uplift of the Himalaya. The Himalayan region hosts over 12 000 flowering plant species, with roughly half being endemic (Wen et al., 2014; Rana & Rawat, 2017). Across the broader Pan-Himalayan region, an impressive 22 183 vascular plant species have been recorded (Liu et al., 2025). Consequently, the region wholly or partially includes three of the world's recognized biodiversity hotspots: the Himalaya, the Mountains of Southwest China, and Indo–Burma. The uplift of the Himalaya played a pivotal role in driving biological diversification by creating new geophysical environments, opening ecological niches, imposing isolation barriers, and acting as natural selection filters, ultimately leading to the formation of new species (Manish & Pandit, 2018; Wu et al., 2022). Abundant fossil evidence further indicates that the Tibetan Plateau served as a globally significant hub for floristic exchange (Zhou et al., 2023). In addition, the formation of the Himalaya and the Tibetan Plateau, along with the intensification of the Asian monsoon system, promoted biodiversity formation and significantly influenced vegetation and biodiversification in eastern China, fostering a synergistic linkage between western and eastern China (Zhang et al., 2024). Qian (2025) used liverwort assemblages distributed along a central Himalayan elevational gradient to test the tropical niche conservatism hypothesis. Their findings revealed that phylogenetic diversity and dispersion decrease with elevation and temperature, supporting the hypothesis. Gui et al. (2025) found that conflicts between cpDNA and nrDNA in Tongoloa (Apiaceae) are likely due to hybridization–introgression and chloroplast capture. Their work highlighted how morphological complexities and evolutionary history have led to taxonomic misplacements in this group. Zhang et al. (2025a) used genomic target enrichment to investigate species relationships, reticulate evolution, and biogeographic diversification of the ginseng genus Panax (Araliaceae). Their findings highlighted the Himalayan–Hengduan Mountains (HHM) as both a refugium and a secondary diversification center, with orographic uplift and climatic changes driving Panax species diversity. Xie et al. (2025b) suggested that incomplete lineage sorting, hybridization, and geographic isolation drove the rapid divergence of Maianthemum in the HHM. Li et al. (2025) revealed that the rise of the Qinghai-Tibet Plateau reduced genetic constraints on Petrocodon (Gesneriaceae) floral architecture, facilitating diverse morphologies shaped by selection for ecological divergence. Huang et al. (2025) studied Lysionotus (Gesneriaceae), identifying the mountain forests of the southern Pan-Himalayan region as a diversity hotspot. Their findings indicate that forest formation and development, coupled with Miocene climatic fluctuations and morphological innovations, drove species diversification. Finally, Zhao et al. (2025) analyzed angiosperm extinction risk in the Sino-Himalaya and Tibetan Plateau using a 21 109-taxon mega-phylogeny and species distribution data. Their analysis demonstrated that evolutionary and environmental factors strongly interact to shape extinction risk, offering valuable insights for predicting trends and guiding targeted conservation strategies. Major mountain systems have garnered significant attention as focal points for studying biodiversity and conservation (Perrigo et al., 2020; Muellner-Riehl et al., 2024). We hope that the collection of articles in this special issue will inspire further research on the majestic Himalaya across the geological, biological, and environmental science community. We are grateful to De-Yuan Hong, Hong-Zhi Kong, Yan Liang, An-Min Lu, Kang-Shan Mao, Jing-Jing Tan, Yu-Fei Wang, Fu-Wen Wei, Tao Su, and Yao-Wu Xing for offering valuable suggestions and their support on the special issue. This work was supported by the National Key Research Development Program of China (2023YFF0805800 and 2022YFF0802300) and the National Natural Science Foundation of China (NSFC 31590822 and 32270233).