Population structure and genetic diversity uncover hidden speciation in an atypical <i>Petunia</i> (Solanaceae) population

Abstract Determining the limits of plant species is often challenging, which complicates efforts to preserve biodiversity, especially in transitional zones or areas in constant change due to human activities. The genus Petunia (Solanaceae) is endemic to the open fields of southern South America, an ecosystem strongly impacted by agriculture and livestock. Despite the importance of this ecosystem to Neotropical biodiversity, the genetic diversity of species from these grasslands is still poorly known. Here, we applied genotyping-by-sequencing to multiple individuals to investigate the genetic diversity and population structure in co-occurring Petunia species, aiming to understand the speciation process. We describe the origin of one atypical population and its evolutionary relationships with other Petunia species. Our results suggest that this genetically and ecologically atypical population could constitute a new species, contributing to the recognition and conservation of biodiversity in an understudied Neotropical region. Furthermore, our study highlights the importance of continually assessing the genetic diversity of various populations, particularly those that diverge ecologically, morphologically, or geographically from typical populations, to understand and conserve biodiversity.