Ecological Vulnerability and Phytochemical Richness of Rheum australe in the Indian Himalayan Region: Insights for Conservation

The Indian Himalayan Region, a globally recognised biodiversity hotspot, supports over 10,000 plant species, including a rich repository of medicinal flora (over 1,700 medicinal plants) integral to ecosystem services and traditional healthcare. Among them, Rheum australe, a high-value medicinal species currently listed as “Data Deficient” on the IUCN Red List, facing escalating threats from overharvesting, climate change, and habitat fragmentation. This study assessed the population status, phytochemical diversity, and habitat suitability to inform targeted conservation strategies. Extensive field surveys were conducted across altitudinal gradients (3200-4200 m amsl) in Uttarakhand using a stratified random sampling. Population data revealed an aggregated distribution pattern, with significant site-wise variation in population density (0.73–1.82 ind./m²) and relative density (0.93-2.48%). A clear increase in population density was observed at higher altitudes, supporting higher density, particularly in rocky crevice habitats. Phytochemical analysis showed notable site-specific variations in total phenolic (2.35-12.70 mg GAE/g DW), flavonoid (6.13-15.30 mg QE/g DW), tannin (1.18-10.60 mg TAE/g DW), and antioxidant activity (DPPH: 2.51- 6.67 mM AAE/100g DW; FRAP: 1.31 - 3.73 mM AAE/100g DW). HPLC profiling identified gallic acid as a predominant polyphenolic compound. A significant positive correlation (p<0.01) between altitude and phytochemical parameters suggested, high-altitude stressors, such as UV radiation and temperature extremes, on secondary metabolite accumulation. Habitat suitability modelling, performed using R Studio software, identified a high habitat probability zone (0.7–0.9) above 3000 m asl, particularly in Uttarakhand, Jammu & Kashmir, and Himachal Pradesh. These findings highlight both ecological vulnerability and phytochemical richness of R. australe, emphasising the urgent need for integrated conservation. In situ conservation should prioritise habitat protection and regulated harvesting, while ex-situ strategies are essential for safeguarding genetic resources.