Persistent foliar anabasine and unusually broad geographic distribution make Nicotiana glauca a distinctive toxicological concern.

Approximately 294 million people live within 10-km grid cells containing recent, georeferenced records of Nicotiana glauca, a widely naturalized poisonous plant associated with severe anabasine-mediated intoxication. Although this spatial overlap does not represent direct human exposure, it highlights the broad geographic extent of potential human-plant encounters. However, it remains unclear whether readily observable plant characteristics, such as developmental stage, leaf morphology, or seasonal condition, can reliably identify plants with consistently low foliar anabasine concentrations. We combined a field survey in three Brazilian localities and longitudinal sampling at one of these localities with comparative phylogenetic and global occurrence analyses to address this question across within-species, evolutionary and geographic scales. All 174 field and longitudinal determinations yielded non-zero estimates, despite substantial quantitative variation among localities and individuals. Within the sampled plants, neither juvenile leaf size, adult collection state nor sampled calendar month identified a condition with consistently low foliar anabasine concentrations. Across 54 Nicotiana species, foliar anabasine showed significant phylogenetic structure (Blomberg's K = 0.59-1.11; Pagel's λ = 0.86-0.93), with consistently elevated standardized scores in Nicotiana section Noctiflorae. Nicotiana glauca ranked second in the cross-study foliar consensus, behind N. noctiflora, but its geographic distribution was markedly broader: 1243 one-degree grid cells across 66 countries, 12.8 times the occupied-cell breadth of the next most widespread high-scoring species. Together, these findings show that the toxicological significance of N. glauca arises from the convergence of persistent foliar anabasine occurrence across sampled conditions, lineage-associated high concentrations and an unusually broad global distribution, rather than from chemical constancy alone.