An escalation toward risk: climate change impacts on the distribution, genetic diversity, and conservation of Neesiochloa barbata (Poaceae: Chloridoideae: Pappophorinae)

Abstract Climate change represents a primary threat to global biodiversity, particularly in seasonally dry tropical forests (SDTF), affecting species distribution, genetic diversity, and ecosystem conservation. Neesiochloa barbata (Poaceae: Chloridoideae: Pappophorinae) is a grass species belonging to a monotypic genus endemic to the Caatinga, the largest SDTF in South America. In this study, we addressed conservation issues related to the impacts of the climate crisis (2080–2100) on the potential distribution, genetic diversity, and structure of N. barbata populations to: (a) assess extinction risk; (b) estimate the future distribution overlap with protected areas (PA); and (c) identify priority areas for conservation. We assessed the current conservation status from Not Evaluated (NE) to Least Concern (LC), however, under future climate scenarios, suitable habitat for N. barbata will be reduced, elevating the threat level to Near Threatened (NT) and finally to Endangered (EN). This severe contraction of climatically suitable areas results in a progressive escalation in extinction risk: LC > NT > EN. Despite the overall loss of suitable habitat, the remaining future niche shows a slight spatial shift toward the boundaries of existing PA (increasing from 39% to 43%). The haplotype network (nrDNA and cpDNA) showed distinct polymorphism rates between the genomes, consistent with the DAPC clustering (best K = 2 and Northern and Southern haplogroups). This genetic structure highlights lineages with distinct evolutionary histories that must be preserved. The reduction in suitable areas and the rising extinction risk underscore the urgent need for targeted conservation in the Caatinga. While the current PA system is crucial for protecting climatic refugia, the expansion and connection of these areas are essential to ensure the long-term persistence and genetic heritage of N. barbata against the climate crisis.