Extremely Rare and Endangered: Genetic Diversity of Nicotiana gandarela (Solanaceae)

The recently described Nicotiana gandarela (Solanaceae) is a wild tobacco with a limiteddistribution, inhabiting shaded areas (shelters) in the rocky outcrops of Serra do Gandarela,south-eastern Brazil. Only a few individuals are known from three occurrence sites, spreadacross different elevations. Our aim in this study was to assess the genetic diversity of N.gandarela across its entire known range. We based our research on high-throughput genomiccoverage and employed a next-generation sequencing method within a population geneticsframework, including multiple individuals of the species. We hypothesised that individualswould cluster according to elevation and that the species would exhibit low genetic diversitydue to its rarity. Unexpectedly, our results showed high diversity indices, mainly due toheterozygous loci, with no population structure evident among the collection sites. Thisindicates gene flow across different elevations, suggesting that the species functions as asingle population. Inbreeding coefficients revealed that individuals are less related thanexpected under random mating, likely due to pollinator behaviour, probably by a small fly.Due to the small number of individuals and the significant human impact on its habitat, thisunusually diverse and rare species faces a high risk of extinction.