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Our understanding of the richness and uniqueness of the flora growing on gypsum substrates in Italy has grown significantly since the 19th century and, even today, new plant species are still being discovered. However, the plants and plant communities, growing on gypsum substrates in Italy, are still a relatively unknown subject.The main aim of this paper was to elaborate a checklist of the Italian gypsophilous flora, to increase knowledge about this peculiar flora and for which conservation efforts need to be addressed.Through a structured group communication process of experts (application of the Delphi technique), a remarkable number of experienced Italian botanists have joined together to select focal plant species linked to gypsum substrates. From the results obtained, 31 plant species behave as absolute or preferent taxa (gypsophytes and gypsoclines) and form the ‘core’ Italian gypsophilous flora. The most abundant life forms were chamaephytes and hemicryptophytes, belonging to Poaceae and Brassicaceae; as for chorotypes, the most represented are Mediterranean and narrow endemics. By improving on previously available information about the flora with a clear preference for gypsum in Italy, this undertaking represents an important contribution to the knowledge of a habitat which is today considered a priority for conservation.

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Abstract. Gypseous substrates are well-recognised as supporting distinctive and unique flora assemblages, including numerous gypsum endemic (gypsophile) species. Along with these, others are also frequent although their presence is not restricted to gypsum; they show a clear preference for them (gypsocline). While this phenomenon (gypsophily) has been studied regionally, and various hypotheses put forward to explain it, there has been little global synthesis. We present a preliminary check-list on the gypsophile and gypsocline flora of the Palaearctic and Australian areas as a part of a project to develop a global checklist of the World's gypsophytes, which can broaden our ecological and biogeographical understanding of these unique environments. The database contains 935 taxa spanning 54 countries. The Irano-Turanian region -and to a lesser extent the Mediterranean region-emerged as the richest territories in terms of gypsophile species; this richness was much reduced in the SaharoArabian and, especially in the Eurosiberian regions. The factors that can modulate the richness of gypsophytes in a region are discussed and have been distributed into four groups: a) geological and edaphic factors; b) factors linked to the insular nature of outcrops; c) climatic variables and their interaction with the soil; d) biogeographical factors. The importance of those factors linked to insularity and, especially, to water availability is emphasized. Because the soil structure of many gypsum outcrops reduces water ability to plants, such outcrops can be regarded as "dry-islands" surrounded by less xeric substrates. The fact that gypsophytes can be grouped within a few major flowering plant clades across continents, confirms their pre-adaptations to these harsh and unique environments. Our work provides a preliminary database for exploring ecological and biogeographic issues relating to gypsophily, and we hope it will stimulate global interest in these valuable ecosystems. Keywords: edaphism; global check-list; gypsicolous; gypsophile; gypsophyte; gypsophily. Un primer inventario de la flora gipsícola del Paleártico y de AustraliaResumen. Los sustratos yesíferos son sobradamente conocidos por presentar cortejos florísticos peculiares y exclusivos, lo que incluye a numerosos endemismos (especies gipsófilas). Junto a estas especies, aparecen otras también muy frecuentes cuya presencia no se restringe al yeso, pero hacia el que muestran una clara preferencia (gipsoclinas). Mientras que este fenómeno (gipsofilia) ha sido estudiado regionalmente, y se han sugerido varias hipótesis para explicarlo, apenas existen síntesis globales sobre el mismo. Aquí se ofrece un inventario preliminar de la flora gipsófila y gipsoclina de los territorios paleártico y australiano como parte de un proyecto que pretende desarrollar una checklist mundial, de manera que se contribuya a ampliar el conocimiento ecológico y biogeográfico de este ambiente único. Este inventario incluye 935 taxa distribuidos por 54 países. La región irano-turaniana -y en meno...

Abstract.-The Betic ranges are recognised as one of the hot spots of biodiversity in the Mediterranean region. The greater part of this territory is in Andalusia and is very rich in vascular plants, some of them endemic. The territory exhibits enormous orographical and geological complexity. This is, in short, a mosaic, fragmented landscape with extremely high b-diversity. This scenario is ideal for monitoring the efficiency of reserve areas. The main aim of this research is to see whether the Network of Natural Protected Areas of Andalusia, extended with the SCIs, is sufficient to safeguard the plant biodiversity, represented in this case by the threatened vascular flora. The analysis includes also the areas corresponding to the priority habitats as defined in the Directive 92/43/EEC. Considering that the presence of priority habitats was a guideline in the drafting of the SCIs, this last inclusion is logical. The results reveal that SCIs are the most efficient strategy for the preservation of the flora, although almost 30% of the flora occur outside these sites. By contrast, the areas with priority habitats failed to cover over 70% of the threatened flora.Key words : priority algorithm -preservation -flora -priority habitats.Résumé.-Les cordillères bétiques ont été reconnues comme l'un des points les plus chauds pour la biodiversité méditerranéenne. Ce territoire abrite une grande richesse floristique et un important endémisme. En effet, il s'agit d'un territoire d'une grande complexité orographique et géologique. En définitive, il s'agit d'un paysage fragmenté en mosaïque d'une grande diversité b. Le principal objectif de cette recherche a été de vérifier si le réseau d'espaces naturels protégés d'Andalousie, augmentés des SIC, est suffisamment efficace pour sauvegarder cette biodiversité végétale vasculaire menacée. En plus de la RENPA et des SIC, on a examiné les habitats prioritaires de la directive 92/43/CEE, élé-ment de base pour la proposition de SIC. Les résultats obtenus ont présenté les SIC comme la stratégie la plus efficace pour cette protection, bien que presque 30% de la flore n'en fassent pas partie. Au contraire, les secteurs à habitats prioritaires recèlent plus de 70% de flore menacée.

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