Riccardo Guarino & Luigi Mossa Floristic, phenologic and chorological differences in the therophytic vegetation-types of Sardinia Abstract Guarino, R. & Mossa L.: Floristic, phenologic and chorological differences in the therophytic vegetation-types of Sardinia. — Bocconea 19: 177-193. 2006. — ISSN 1120-4060. The therophytic flora of Sardinia has been split into four main groups, basing on the ecologic requirements of species. The following groups have been recognized: flora of dry entisoils, flora of periodically swampy or submerged entisoils, flora of coastal sites, flora of fields, road edges and human settlements. Either, most frequent or exclusive species were ascribed to each group. A species was considered “exclusive” when its relative frequency outside a given group was estimated ?10%. Differences have been highlighted within the groups, dealing with chorol- ogy, growth form, flowering time, colour of flowers, pollination and seed dispersal strategies. Introduction The abundance of therophytes largely contributes to the naturalistic value of Sardinia. Moreover, most of the annual species belonging to the Sardinian flora also have an histor- ical and cultural value, as in most cases their occurrence reflects different ways of tradi- tional land management and exploitation of natural resources, that are still performed on the island. Indeed, the development of human technology increased number and frequen- cy of the annual plants of Sardinia over 10 thousand years of civilisation. At present, therophytes count about 40% of the Sardinian flora (Camarda 1984a; Bocchieri 1995): they occur in several habitats of the island, where they play a keystone role, both as biomass producers and protecting the soil from rill erosion during the rainy season, at least where the environmental factors do not let a thick layer of perennial plants. In the frame of a research about the ephemeral flora and vegetation of Sardinia, an updated checklist of the therophytes occurring on the island has been recently edited by Mossa & Guarino (in press). The list, counting 862 ascertained species, was based on over 250 bibliographic references, integrated with data concerning collections in the field. For each record of the check-list, information was provided about chorology, growth form, flowering time, colour of the flowers, pollination, seed dispersal strategies, habitat require- ments and rarity. Aim of this paper is to distinguish, within the check-list, groups of species having a similar ecologic specialisation and to characterize them by means of the above-