Conservation of Ptilostemon greuteri (Asteraceae), an enigmatic climate relict from Sicily (Italy): state of the knowledge after the discovery of a second population.

Ptilostemon greuteri is one of the most endangered and poorly studied woody vascular plant species of the Mediterranean Basin, endemic to Sicily (Italy). Several peculiar traits confer to P. greuteri a character of uniqueness and an enigmatic attractiveness. In fact, at first glimpse the largest individuals of this species remind the most remarkable and peculiar cases of herbaceous genera (e. g., Echium, Senecio) turned woody on insular or insular-like mountain ecosystems. Following the discovery of a second population of this rare species, a project aiming at the study and conservation of P. greuteri was set up. We present here updated information on the distribution, conservation status, biology and ecological requirements of this species. Field surveys supported by drone imagery were carried out to estimate the current range of the two populations. The data obtained allowed to refine the conservation status assessment of the species and to update the distribution pattern of P. greuteri by means of detailed digital maps of each population. Ongoing field investigations currently provide valuable information about the ecological requirements of the species and point out the impact of wildfires on population size and structure. Our research has also highlighted several knowledge gaps that need to be filled to apply more effective conservation measures. Preliminary results suggest that local topographic and mesoclimatic factors (air humidity and shade) are key variables explaining the persistency and survival of P. greuteri in the area.