Community composition and spatial aggregation patterns of the endangered endemic plant Menonvillea linearifolia (Brassicaceae) in the Atacama Desert

Menonvillea linearifolia is an endangered annual herb endemic to north-central Chile, growing on sandy coastal slopes within the Atacama Desert flowering zone. To characterise its ecological context, we surveyed the floristic composition, plant cover and spatial aggregation patterns of its associated plant community in Punta de Choros, Coquimbo Region, during a flowering desert event. Using 20 transects and 1,000 microplots, we recorded 29 vascular plant species, with a dominance of annual herbs (44.8%) and high endemism (79.3%). The community exhibited strong dominance of Cistanthe longiscapa, whereas most species occurred at low cover and in scattered patches. Spatial analyses (variance-to-mean ratio, Morisita, Green and negative binomial indices) revealed predominantly aggregated distributions. In particular, Menonvillea linearifolia, Alstroemeria werdermannii, Echinopsis deserticola and Heliotropium floridum were highly aggregated, reflecting limited dispersal and dependence on specific microhabitats. These traits make M. linearifolia particularly vulnerable to disturbances, including off-road vehicle use, grazing, mining expansion, and climatic variability. The results emphasize the importance of protecting key microhabitats and incorporating spatial structure into conservation strategies. This study provides the first quantitative ecological baseline for M. linearifolia, supporting targeted habitat management and conservation actions in the Atacama flowering desert ecosystems.