Climatic relict plants and syntaxonomical classification: a case study from Sicily (Italy)

Ptilostemon greuteri is one of the most intriguing narrow endemic plant species of the Mediterranean Basin. At first glimpse, the largest individuals of this species remind the most remarkable and weird cases of herbaceous genera (e.g., Echium, Senecio) turned woody on insular or insular-like mountain ecosystems. This woody thistle is only known from two populations mostly growing on NNE-facing calcareous cliffs and ledges on the NW coast of Sicily (Italy) and can be considered a climatic relict. To better understand its ecology for conservation purpose, we carried out a study at community level to investigate in which plant communities does P. greuteri lives, which species/life form are most frequently associated with it and which microtopographic variables are influencing the distribution of the communities where P. greuteri lives. The analysis of vegetation relevés collected along four transects showed that P.greuteri lives in different plant communities, being positively associated with species belonging to several syntaxa, and preferring shady environmental conditions. Our results suggest that relict species are difficult to frame into syntaxonomical classification, because they represent the last remnants of a vegetation type that disappeared.