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Islands and plants: preservation and understanding of flora on Mediterranean islands

species richness, biogeographic and conservation
interest of the vascular flora of THE SATELLITE islands

OF SICILY: PATTERNS, DRIVING FORCES and threats

Salvatore Pasta1 and Tommaso La Mantia2
1Consiglio Nazionale delle Ricerche, Istituto di Genetica Vegetale, Corso Calatafimi n°
414, I-90129 Palermo, Italy.
2Dipartimento SAF, Viale delle Scienze, Ed. 4, Ingr. H, 90128 Palermo.

Abstract
The vascular flora has been investigated on about 60 of the approximately

100 islands and islets of the Sicilian archipelago. This paper provides detailed
information on the number of exclusive, rare, or threatened vascular plants
living on these islands and islets. Focusing on the 18 most-investigated islets,
we evaluate the extent to which species richness, rate of endemism, number
of alien plants, and number of terrestrial habitats have been influenced by
1) geographical setting, 2) geological history, 3) geo-pedological variability,
4) bioclimate, 5) number and patchiness of local plant communities, and 6)
natural and human disturbance history and regime. Special attention is directed
to the rarefaction and extinction of many interesting species that live or have
lived only on these islands. Rarefaction and extinction are mostly linked to
the increase in anthropogenic disturbance, which have caused the destruction,
degradation, and/or fragmentation of many plant communities and especially
those associated with rocky or sandy shores and temporary ponds. Interestingly,
in some cases extinction has resulted from a reduction in certain human
activities. For example, many noteworthy species are disappearing with the
abandonment of traditional land uses that created low-impact agro-ecosystems,
new microhabitats (e.g., stone walls), and open semi-natural habitats (including
vineyards, cereal crops, olive groves, and fallows subject to extensive grazing).

Finally, we emphasize the need for current information about species
turnover, invasion processes, and demographic patterns of the vascular flora
of those islands and islets that support the most fragile communities and/or
species.

Keywords: species richness, rate of endemism, 92/43 EU Directive, conservation
policies, island biogeography

Corresponding author: Salvatore Pasta (salvatore.pasta@igv.cnr.it)
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