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The vascular flora of the satellite islands of Sicily

This paper provides an overview on the number of exclusive, rare, or
threatened vascular plants living on the circum-Sicilian islands and islets, and
focuses 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 a number of abiotic and biotic
factors. We pay special attention to those species whose numbers have been
decreasing and that are threatened with extinction.

WHICH FACTORS ARE RESPONSIBLE FOR THE FLORISTIC
DIVERSITY OF THE CIRCUM-SICILIAN SATELLITE ISLANDS AND
ISLETS?

Many papers have emphasized the high phytogeographic importance of
Sicilian plant heritage (Di Martino & Raimondo, 1979; Nimis, 1985; Brullo et
al., 1995; Brullo et al., 2013) but only a few have focused on the major role
played by the satellite islands (Pasta, 1997; Mazzola et al., 2002; Raimondo,
2004; Bocchieri & Iiriti, 2011; Troìa et al., 2012; Troìa, 2012). The recorded high
values of both species-richness and endemism depend on six main factors: 1)
geographical setting; 2) geological (and geological disturbance) history; 3) geo-
pedological variability; 4) bioclimatic belts; 5) number and patchiness of local
plant communities; and 6) natural and human disturbance history and regime.
Basic data on some of these factors are provided in Table 3, while additional
information on their effects is provided in the following paragraphs.

Geographical setting
The circum-Sicilian islands (Figure 1) have a wide latitudinal range and
extend from Lampedusa in the Pelagie Archipelago (at 35°30’ N) to the south
and Strombolicchio in the Aeolian Archipelago (at 38°50’ N) to the north. The
Strait of Messina (which is 3 km wide) currently separates Sicily from Eurasia,
while the nearest part of Africa (Tunisia) is about 70 km from the island of
Pantelleria. These separations may have been less significant or non-existent at
some times in the geologic past. Plio-Pleistocenic climate change, for example,
may have favoured direct plant migration between Sicily and both Eurasia and
Africa. In fact, during the Last Glacial Maximum (hereinafter LGM, about
18-12 Kya), the sea level was some 80–120 m lower than today (Lambeck et
al., 2010), so that the Egadi Islands, Sicily, and the Maltese Archipelago were
united; Lampedusa and Lampione were part of Africa; and Pantelleria was
less than 10 km from Sicily. Hence, the complex history of past connection
and proximity between Sicily and nearby territories may have greatly affected

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