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

Bioclimatic belts
Although circum-Sicilian islets host very few weather stations, the models
provided by Drago (2002) indicate that they harbour three bioclimatic
thermotypes (sensu Rivas-Martínez, 2008) whose distribution (Figure 1) mostly
depends on latitude and altitude. The harshest thermotype, infra-mediterranean,
occurs on the islets in the Strait of Sicily (the whole Pelagian Archipelago and
the lowest part of the Egadi islands and Pantelleria). The thermo-mediterranean
thermotype is widespread up to 450 m a.s.l. on all the satellite islands. The tops
of the major islands (i.e., Pantelleria, Marettimo, Alicudi, Filicudi, Lipari, Salina,
and Stromboli) that exceed 600 m a.s.l. experience the meso-mediterranean
thermotype. Moreover, a very humid microclimate occurs on the top (> 800 m
a.s.l.) of Pantelleria, Salina, and Stromboli.
In the absence of anthropogenic disturbance, those circum-Sicilian islets that
are subject to the infra or thermo-mediterranean climate should be covered by
a discontinuous maquis dominated by evergreen or summer-deciduous shrubs
(e.g., Anagyris foetida, Euphorbia dendroides, Lycium intricatum, Periploca
angustifolia, Rhus pentaphylla) and a few conifers like Pinus halepensis and
Juniperus turbinata, while the meso-mediterranean belt should be dominated
by thermophilous oak woods containing Quercus ilex, Q. suber, and Q. virgiliana
(and Pinus pinaster subsp. hamiltonii at Pantelleria).
According to many recent studies of the Pleistocene (Agnesi et al., 2000;
Incarbona et al., 2010), glacial maxima probably coincided with very arid
conditions in the central Mediterranean, so that the most widespread Sicilian
natural landscape was a savannah with very scattered tree cover (Noti et al.,
2009; Tinner et al., 2009). On the other hand, several works focusing on the
genetic diversity of woody trees have highlighted the special role played by the
main island; the canyons and the mountain ranges facing the northern coast
acted as refugia because of their humid meso and microclimate (Dumolin-
Lapègue et al., 1997; Hewitt, 1999; Fineschi et al., 2005; ecc.). The same role
could have been played by satellite islands, which still host some exceptionally
isolated species such as Pseudoscabiosa limonifolia (Devesa, 1984), Bupleurum
dianthifolium (Neves & Watson, 2004), Cytisus aeolicus (Cristofolini & Troìa,
2006), and Eokochia saxicola (Kadereit & Freitag, 2011).
Number and patchiness of local plant communities
Table 4 outlines the high heterogeneity of the natural landscape of 18 circum-
Sicilian islets. In fact, these islets host 29 different habitats of community
interest according to the 92/43 EU Directive. The large number of niches and

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