Format: ORAL

Orsenigo Simone1; Giacomo Baldesi1, Carla Lambertini2; Fainelli Federico1

1 Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy 2 Department of Biosciences, University of Milan, Milan, Italy

Hieracium is one of the largest plant genera in the Angiosperms and experienced a rapid and recent evolutionary radiation. Due to the massive morphological variation among species, past hybridization events and frequent polyploidization, combined with apomictic reproduction in polyploids, the species concept in Hieracium is widely debated and species identification is very challenging. According to recent studies1 most vulnerable species are found within young and fast-evolving plant lineages and several Hieracium species are considered extinct or threatened2. Taxonomy represents the first fundamental step for every conservation project. Taxonomic investigation can lead to changes in conservation status or to de-extinctions of species3. Taxa with doubtful classification are particularly sensitive to this kind of problems. Hieracium tolstoii Fen. Zahn was a narrow endemic species described for the ancient walls of Milan Castle (Italy). Morphologically, this species was considered as intermediate between two other species (H. pospichalii and H. australe). However, no further investigations were conducted on H. tolstoii origin after the first description in early XX century and nowadays the species is considered extinct3. To verify the nomenclatural identity of H. tolstoii, disentangle its origin and ensure the validity of its current conservation status, we conducted a taxonomic investigation on herbaria specimens of the early XX century. Specimens were studied by morphometric analysis comparing H. tolstoii with H. australe, H. pospichalii, and other closely related species. Finally, we performed phylogenetic investigations using three plastid intergenic spacers (trnH-psbA, trnT-trnL, and trnV-ndhC) and ten nuclear microsatellites to evaluate the genetic relationship between species and assess the possibility of hybrid origin of H. tolstoii. 1Davies et al. (2011), PLOS Biology, 9(5):e1000620 2Abeli et al. (2021),Nature Plants, 7(3):282-286 3 Orsenigo et al. (2021), Plant Biosystems,155(2):310-335