Habitat suitability modeling for the conservation of Exacum bicolor Roxb.: An endangered, medicinal and ornamental species of Kerala’s lateritic hillocks under current and future climatic scenarios

Exacum bicolor Roxb. (Gentianaceae) is a perennial herb with striking flowers and medicinal beneficial properties. Endemic to Peninsular India, it is currently listed as endangered. Despite its aesthetic and therapeutic value, the species remains underexplored and underutilized. Preserving the genetic diversity through in-situ or ex-situ conservation is essential to meet the growing demand for its medicinal and ornamental uses. A Maximum Entropy (MaxEnt) modeling approach was used to estimate the potential distribution of E. bicolor in Kerala, India, considering both present and future climatic scenarios, due to its efficiency with presence-only data. The MaxEnt model predicted habitat suitability for E. bicolor with an area of approximately 1126 km², showing high probability zones concentrated in the northern parts of Kerala. To evaluate habitat suitability, 22 environment parameters - including bioclimatic variables, soil types, agroecological zones, topographical features - were incorporated into the MaxEnt model. The most influential variables were precipitation of driest quarter (Bio17), water vapour pressure (January), annual precipitation (Bio12), mean diurnal range (Bio2), solar radiation (July and March), Topographic Position Index (TPI) and slope. Habitat suitability for E. bicolor was projected under future climate scenarios (2020-2100) using Shared Socioeconomic Pathways (SSPs) 126, 245, 370 and 585. In the SSP585 scenario, highly suitable areas for E. bicolor are anticipated to decrease by 14.20 % during the period of 2080-2100 compared to the current scenario. This decline is likely attributed to rising temperatures and decreasing rainfall, underscoring the need for climate-resilient conservation planning.