Research Highlights
Plant Ecology and Evolutionary Biology
Predicting invasion risk model of wild sugarcane (Saccharum spontaneum)
1. CABI Compendium
This datasheet on Saccharum spontaneum covers Impact, Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Dispersal, Hosts/Species Affected, Vectors & Intermediate Hosts, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control and Further Information.(https://www.cabidigitallibrary.org/doi/full/10.1079/cabicompendium.48162)
Pleistocene glaciation-driven diversification
This study investigates the speciation dynamics of Stellera chamaejasme L. in Southwest China's mountains, a region recognized for its rich biodiversity but increasingly threatened by climate change. While past research suggested a long timeline for plant diversification spanning over 10 million years, our findings reveal that the diversification of this species occurred much more recently, around 2.67–0.90 million years ago, influenced by Pleistocene glaciation and climatic fluctuations. Using genomic and eco-morphological data, we identified four cryptic species that had previously gone unrecognized due to their subtle morphological differences. These species have evolved in large, distinct metapopulations, shaped by historical allopatric speciation and cyclical warming–cooling episodes along elevational gradients. This refined timeline challenges earlier views of ancient speciation and highlights the vulnerability of alpine species to future climate change, emphasizing the urgent need for targeted conservation efforts to protect these ecosystems.
Rana et al. (2024) Journal of Integrative Plant Biology (https://doi.org/10.1111/jipb.13663)
Genomic signatures of habitat isolation and paleo-climate unveil the “island-like” pattern in the glasshouse plant Rheum nobile
The Himalaya-Hengduan Mountains (HHM), known as 'Sky Islands,' offer a unique opportunity to study the genomic differentiation of endemic plants and their “island-like” genetic distinctness. Despite the region's ecological importance, the underlying mechanisms remain poorly understood. This study examines Rheum nobile, a species from the alpine subnival summits of HHM, to explore the genetic dynamics contributing to its distinct structure. Analysis of plastome and Internal Transcribed Spacer (ITS) sequences from 104 samples revealed high genetic diversity and unique alleles, aligning with three phylogroups that reflect the floristic regionalization of HHM. These lineages diverged 7.72–4.18 million years ago, with a population bottleneck occurring between 0.18–0.016 million years ago (plastome) and 0.38–0.031 million years ago (ITS). No correlation was found between genetic patterns and geographic distance or environment, and limited gene flow occurred between phylogroups. Ensemble Species Distribution Modeling (eSDM) suggested multiple refugia during or before the Last Glacial Maximum, highlighting the species’ complex historical distribution. This research reveals the role of fragmented 'Sky Island' habitats and prolonged isolation in shaping R. nobile's genetic structure, with important implications for its conservation.
Rana et al. (2025; Global Ecology and COnservation). https://www.sciencedirect.com/science/article/pii/S2351989425000721
Biogeographic barriers for the divergence and differentiation of Koenigia forrestii (Rana HK)
The interaction between orographic and climatic changes in the Himalaya–Hengduan Mountains has created biogeographic barriers that led to the allopatric differentiation of plant species. This study investigates the long-term Neogene–Quaternary geo-climatic history of the Eastern Himalaya–Hengduan Mountains, focusing on the narrow distributions of Koenigia forrestii. Ten populations (97 individuals) were sampled and analyzed for their genetic structure, including phylogenetic reconstruction based on plastome, plastid DNA, and nuclear regions, molecular dating, demography, and niche dynamics. Our findings suggest that K. forrestii (stem age: 11.39 million years) diverged into three distinct lineages between 5.84–2.57 million years ago, with the Eastern Himalaya (EHa) lineage being the first and most diverse. "Isolation by environment" revealed significant genetic structure influenced by environmental variation. Bayesian skyline plot analysis supports recent demographic expansion, while lineage divergence was mainly driven by the heterogeneous environment, shaped by biogeographic barriers such as the Tsangpo-Brahmaputra Grand Canyon, Mekong-Salween Divide, and local mountain ranges. Niche shifts and local adaptation were key factors in determining the genetic structure, demographic patterns, and diversification history of K. forrestii.
Rana et al. (2023); https://doi.org/10.1093/botlinnean/boac045
Evolutionary history of Incarvillea
and population genetic connectivity of Incarvillea; Population genetic connectivity of Mirabilis himalaica (Rana HK); Phylogeography of rare fern Polystichum glaciale (Luo D)
Evolutionary history of Incarvillea
Genus-level phylogenomics and biogeography indicate Incarvillea is monophyletic, with a Central Asian origin in the mid-Oligocene (~29.4 Ma). Early Miocene diversification split lineages toward the western Himalaya and the Sino-Himalaya, consistent with QTP/Hengduan uplift and subsequent climatic shifts driving range expansion and trait evolution. Intraspecific work (e.g., I. sinensis) shows deep cpDNA lineage divergence (southern/eastern QTP vs. northern ranges) dating to ~4.4 Ma, linking spatial genetic structure to mountain building and Quaternary climate oscillations.
Population genetic connectivity of Incarvillea
Landscape–genetic studies in the HHM hotspot (e.g., I. arguta) combine cpDNA/low-copy nuclear markers with ensemble SDMs and least-cost paths to map corridors and barriers. Geoclimatic factors (topographic relief, river systems, passes) better explain connectivity than simple geographic distance, revealing discrete dispersal routes threaded through valleys and gorges. For I. sinensis, strong structure and allopatric lineages imply limited contemporary gene flow across major physiographic breaks; southern (eastern QTP) populations harbor higher diversity, consistent with long-term refugia and post-glacial recolonization to the north and east.
Population genetic connectivity of Mirabilis himalaica (Rana HK)
Range-wide sampling (241 individuals, 29 populations) using four cpDNA regions + nuclear G3pdh resolved four spatially structured phylogroups with diversification beginning in the late Pliocene (~3.6 Ma). No recent demographic expansion was detected. Integrating phylogeography with SDMs and least-cost path analysis showed that river drainages, intermontane valleys, and mountain gorges act as key dispersal corridors from the Last Interglacial through the LGM to the present—and are projected to remain important—while recent uplift and monsoon changes fragmented habitats and constrained long-distance dispersal.
Ecological Niche Modeling
Hotspots of grassland suitability for restoration
This project focuses on the complex relationship between species distributions and climate, aiming to inform and improve grassland restoration efforts as climate change progresses. By using ensemble species distribution modeling (eSDM), researchers examined habitat suitability for 26 grassland species frequently used in restoration. The goal was to identify the key bioclimatic factors shaping these species' distributions and predict how habitat suitability may change by 2050. The analysis spotlighted temperature and precipitation during the warmest quarters as critical variables, suggesting that changes in these factors could profoundly impact grassland ecosystems.
The project identified current and future hotspots of habitat suitability for diverse grassland species and functional groups. These hotspots, centered mainly in Minnesota, North Dakota, and South Dakota, are projected to shift northward under warming scenarios. By overlaying these hotspots with maps of landscape connectivity and protected status, the project revealed that suitable habitats often lack both protection and connectivity. This insight underscores the need for targeted restoration and conservation actions in these areas, especially in anticipation of climate-induced range shifts.
Ultimately, this research emphasizes a forward-looking approach to restoration management, encouraging the use of climate-informed hotspots to prioritize seed sourcing and restoration initiatives. By focusing on areas where connectivity and protection are lacking, restoration efforts can be better aligned to maintain functional and resilient grassland ecosystems, ensuring their viability in an uncertain climate future.
Rana et al. (2024; preprint)
Distribution modeling of two alpine glasshouse species
This project uses ensemble species distribution modeling (eSDM) to explore the historical, present, and future distribution of two alpine "glasshouse" species, Rheum nobile and Rheum alexandrae, under various climate scenarios. Both species have adapted to alpine environments but show distinct geographic ranges: R. nobile is predicted to extend from the Eastern Himalaya (EH) into the Hengduan Mountains (HM), while R. alexandrae remains limited to the HM. Modeling results reveal significant range shifts for both species, driven largely by changes in precipitation rather than temperature.
In response to climate changes since the last glacial period, both species are predicted to move northward and upward in elevation, reflecting a trend that is expected to continue with future climate shifts. Interestingly, the models show an initial northward expansion of suitable habitats followed by a southern retreat within the HM region. Although niche overlap analyses suggest that these two species occupy distinct ecological niches, there is some convergence in specific HM areas.
This study highlights the precarious future of R. nobile and R. alexandrae, as their suitable habitats shift to northern and higher elevations. However, their survival may be challenged by extreme alpine conditions despite favorable location shifts. Thus, this work calls for targeted conservation strategies in these critical biodiversity hotspots to support these unique alpine species under projected climate conditions. Rana et al., (2022)
Himalayan Incarvillea Juss.
Our project investigates the impact of global climate change on mountain biodiversity, focusing on the resilience and range shifts of species in high-altitude regions. Using the Himalayan Incarvillea genus as a model, we explore the "Nowhere to go" hypothesis, which predicts that alpine plants face intensified competition and limited range expansion opportunities as warming conditions allow new colonizers into high-altitude habitats. To assess potential range shifts, we employed a multi-model median (MMM) ensemble species distribution model (eSDM), incorporating 13 climatic and 15 environmental variables alongside 542 rarefied occurrence records of Incarvillea species. We also used principal component analysis (PCA) and discriminant function analysis (DFA) to evaluate the environmental drivers behind ecological divergence within the genus. Under four projected climate scenarios, our model suggests a northwestern range expansion for Incarvillea within key Asian biodiversity hotspots, though the occupied niche range may not fully meet the predicted outcomes of the "Nowhere to go" hypothesis. This research provides valuable insights into how climate-induced changes could reshape biodiversity in mountain ecosystems, informing future biogeography and conservation strategies in these critical habitats. (Rana et al., 2021)
Medicinal and aromatic plants of Nepal
This project addresses the urgent need for effective conservation and sustainable management of valuable Himalayan medicinal plants under climate change pressures and unsustainable extraction practices. We focus on Neopicrorhiza scrophulariiflora, a high-demand plant at risk of depletion due to trade pressures, and examine its habitat suitability in Nepal. Our species distribution modeling reveals a narrow range of suitable elevations (4000-4400m) largely in eastern Nepal, with less suitable habitats dominating the western regions where trade activity is highest, underscoring the unsustainable nature of current harvesting patterns. Additionally, ensemble modeling of six other prioritized medicinal plants, including Nardostachys jatamansi and Aconitum spicatum, maps current and future suitability zones. The models indicate a core hotspot for cultivation in central Nepal at mid- to high altitudes, ideal for combating trade-induced pressures. For two threatened species, Fritillaria cirrhosa and Lilium nepalense, MaxEnt projections show a significant habitat shift to the northwest by 2050. Together, these results inform strategies for habitat conservation, local farming practices, and sustainable harvesting limits that are essential to safeguard these critical medicinal resources and benefit rural livelihoods. (Rana et al., 2020; Poudeyal et al., 2021; Rana et al., 2017)
Bioclimatic space of Himalayan alder
The Himalayan alder species, Alnus nepalensis and Alnus nitida, play a crucial role in agroforestry and land restoration across Nepal, offering nitrogen fixation that benefits soil health and agricultural productivity. This project mapped the current and future suitable habitat for these species using climate models in MaxEnt software, integrating bioclimatic and topographic variables, along with Land Use Land Cover (LULC) data. Our findings indicate that central Nepal, especially the moist north-west facing slopes, is highly favorable for A. nepalensis, while western Nepal provides optimal conditions for A. nitida. Key environmental drivers of their distribution include seasonal precipitation patterns: the warmest quarter for A. nepalensis and the driest for A. nitida. Using Earth System Models (ESMs) for future projections, we identified regions where the probability of their growth remains stable, highlighting areas for conservation and new agroforestry initiatives. This model also underscores opportunities for using alder species to strengthen traditional agroforestry practices and to source material for effective land restoration in Nepal's hilly regions. (Rana et al., 2018)
Plant Systematics and Biodiversity
Industrial floristic inventories valuable for resolving taxonomic ambiguity? A test case in the genus Glandularia: Verbenaceae.
New species Saussurea talungensis HK Rana and SK Ghimire.
A recent alpine botanical survey in the Talung Valley, Humla District, NW Nepal led to the description of Saussurea talungensis S.K.Ghimire & H.K.Rana, a high‐elevation (ca. 4300 m) species of Saussurea sect. Strictae distinguished by its longer leaf petioles, purplish‐tinged margins, and 1–3 capitula per stem. Chloroplast genome analysis placed it as sister to S. roylei, and its restricted range (< 500 m², ~50 mature individuals) prompted a preliminary IUCN assessment as Critically Endangered. However, subsequent morphological reassessment and plastome comparison revealed these traits fall within the intraspecific variation of S. roylei, leading to its recent treatment as a synonym. This case highlights the importance of integrating detailed field morphology with genomic data and broad herbarium comparisons to refine species delimitations in morphologically variable alpine taxa.
Temperate Himalayan peatland
We provided a seminal review of Khecheopalri, a temperate peatland nestled in the Eastern Himalayas, Sikkim, India. This peatland—formed after the Last Glacial Maximum—hosts a broad spectrum of biodiversity, featuring 682 species across five kingdoms, 196 families, and 453 genera. The site’s hydrology follows a monsoon-dominated pattern (approximately 85% of its ~2100 mm average annual rainfall arrives during the monsoon) and is both ecologically and culturally significant, being central to local indigenous groups and proposed for recognition under both Ramsar and UNESCO designations.This work offers the first comprehensive ecological baseline for Himalayan peatlands, crucial for tracking anthropogenic disturbances—such as infrastructure development and tourism—that have altered the site since the late 1980s. It underscores the pressing need for systematic biodiversity assessments and hydrological monitoring to inform adaptive conservation strategies across the region.
(O’Neill et al. (2020); Wetland Ecology and Management