Abstract
Contribution to the vascular flora of Castelvecchio Nature Reserve (central Tuscany, Italy). This study reports the outcomes of botanical surveys of vascular plants carried out in the Castelvecchio Nature Reserve, located in the Municipality of San Gimignano (Siena province). The Reserve has an extension of 6.28 km2 with a predominance of calcareous bedrock. The compiled floristic inventory of the Reserve includes 454 species and subspecies, divided into 73 families and 185 genera. Data on life forms and chorological types are provided. The life-form spectrum revealed a dominance of hemicryptophytes followed by terophytes, whereas the chorological spectrum showed a majority of species with Eurasiatic distribution as opposed to a Mediterranean one, in line with the local macro and microclimatic conditions. Rare species in central Tuscany - such as Cleistogenes serotina subsp. serotina, Ononis natrix and Phagnalon sordidum - and two species on the Italian Red List - Galanthus nivalis and Ruscus aculeatus - were recorded. Also of interest is the occurrence of phytogeographically relevant entities as Taxus baccata and populations of Fagus sylvatica subsp. sylvatica outside of its altitudinal belt. Compared to other areas of central and southern Tuscany, the Italian endemics - Digitalis micrantha, Helleborus viridis subsp. bocconei, Hieracium pallidum subsp. lanudae, Melampyrum italicum, Polygala flavescens subsp. flavescens, Scabiosa uniseta - were less numerous. The Reserve does not have a species pool typical of limestone as other protected areas of central or southern Tuscany. However, the mosaic of different communities, combined with geological and microclimatic factors, makes the Reserve highly relevant for the conservation of biodiversity in central Tuscany. Its peculiarity is the presence of isolated populations of mesophilous species that are confined to ravines with a cool microclimate and are in contact with xerophilous species of calcareous garrigues. Besides a valuable heterogeneity of environments in the Reserve it is worth nothing that there are only fourteen alien species, mainly with a casual status of invasivity.