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The Balearic Islands are an archipelago of five major islands and other minor islets placed in the western Mediterranean, southeast of the Catalonian coasts. The archipelago covers a surface of 4992 km2 and its coastlines stretch for 1,428 km. Only the major island, Mallorca, is characterized by the presence of true mountain ranges, the Serra de Llevant and the Serra de Tramuntana whose highest peak is the Puig Major (1,445 m a.s.l.).
The Balearic bioclimate falls in the Mediterranean pluviseasonal oceanic and only in part in the Mediterranean xeric oceanic (Rivas-Martínez, 2008). The thermotype is mainly Thermomediterranean while the Mesomediterranean can be found in the reliefs and the Supramediterranean only in the highest peaks.
The Balearic flora displays 2089 taxa of which 173 endemics (Rita Larrucea et Payeras Coll, 2006).
Corsica covers a surface of 8,748 km² with approximately 1,000 km of coastlines and stretches along the North-South direction in the Ligurian Sea north of Sardinia and south of the Gulf of Genova. From a geomorphological point of view, Corsica can be described as a mountain in the sea being its territory mainly mountainous with fewer flatlands and having its highest mountain represented by Monte Cintu (2,710 m a.s.l.).
The most representative bioclimate is the Mediterranean pluviseasonal while thermotype ranges from Themomediterranean to alpine (Jeanmonod et Gamisans, 2013).
The Corsican flora amounts to 2724 taxa, of which 302 are endemic (13.49%). Endemics are represented by 132 exclusive units, 78 Corso-Sardinian taxa, 19 taxa of which belong to the Italian-Tyrrhenian superprovince, 7 taxa which can be found in both Corsica and the Balearic Islands, while other endemics belong also to other adjacent areas (Jeanmonod et Gamisans, 2013).
Concerning rarity, according to Jeanmonod et Gamisans (2013) 415 taxa, of which 53 endemics, can be defined as very rare (5 or less localities) while 275 taxa, of which 33 endemics, are rare (6 to 10 localities).
Sardinia, placed at the center of the Thyrrenian Sea, covers a surface of 24,089 km² and is the second largest island in the whole basin after Sicily. The high mountain of Sardinia is represented by the Gennargentu massif whose highest peak is Punta la Marmora 1,834 m a.s.l. Its territory is divided into seven regions that approximately correspond to the same number of morphological regions.
According to Rivas-Martínez (2008), the Sardinian climate can be described as oceanic on the basis of the continentality index and principally set in the semihyperoceanic, the euoceanic and in the semicontinental subtype, while the most representative bioclimate is the Mediterranean pluviseasonal oceanic (MPO). Three thermotypes characterize the MPO: the upper Thermomediterranean, the lower and upper Mesomediterranean and the lower Supramediterranean. Different ombrotype have been reported for Sardinia: the upper and lower dry, the lower and upper subhumid and the lower humid ones (Bacchetta et al., 2009).
Sardinian flora, after the latest floristic researches, counts more than 3,000 taxa, of which 347 are endemic (e.g. narrow endemics, Sardinian endemics, Corso-Sardinian endemics, Corso-Sardinian-Balearic endemics) with 45.8% (183 taxa) being exclusive endemics (Fenu et al., 2014). 291 taxa are included in the regional Red List of Italy and are distributed in the following IUCN categories: 5 EW, 39 CR, 41 EN, 69 VU, 119 LR, 17 DD and 1 NE. Sardinian endemics are mostly located in coastal habitats, both sandy and rocky, and on mountain ranges, where the ecological insularity and the local isolation have led to a notable speciation. Unfortunately, these habitats are among those that are mostly threatened by tourism, exaggerated land use, recurrent fires, invasive alien plants species and global warming.
A number of ecosystems and natural habitats have been considered of great importance for plant conservation in Sardinia, e.g. its 15 Special Protection Areas (SPA), 92 Site of Community Importance (SCI) and 34 Important Plant Areas (IPAs). Despite that, they are still not under protection or, at least, not for the entirety of their area, nor a dedicated law has been enacted to preserve the Sardinian flora and its natural habitats. Being considered itself part of the Tyrrhenian Islands hotspot (Médail et Quézel 1997, 1999), the Sardinian endemic flora has been recently studied by Cañadas et al. (2014), who pinpointed three areas that well fit the concept of the so-called micro-hotspot: Iglesiente (South-western Sardinia), Supramontes, and Gennargentu (Central-eastern Sardinia), the latter containing nine nano-hotspots.
Sicily, located in the center of the Mediterranean, is the largest island in the basin covering an area of 25,711 km2 with a coastline length of 1,484 km. Sicily constitutes a sort of continuation of the southern Apennines with its highest mountain ranges located in the northern part of the island, while the highest peak is represented by the volcano Mt. Etna (currently 3,320 m a.s.l.).
The bioclimate that characterizes Sicily is Mediterranean pluviseasonal oceanic, while thermotype at low elevation is mainly Thermomediterranean with a transition to the Mesomediterranean and the Supramediterranean as elevation rises up. Oromediterranean and Cryo-oromediterranean thermothypes are circumscribed to the highest part of Mt. Etna (above 2,000 m a.s.l.).
Regarding the floristic richness of Sicily, the vascular flora is currently estimated to consist of about 3,200 taxa (Giardina et al., 2007; Raimondo et al., 2009) with about 350 narrow endemics (i.e. exclusively occurring in Sicily). From a conservation point of view, following the latest IUCN categories and criteria, 431 taxa, corresponding to about the 13.4% of Sicilian flora, are threatened falling within the categories CR, EN, and VU, and additional 286 taxa are classified as LR.
Currently, five regional parks are established in Sicily: Mt. Etna (58,095 ha), Mts. Madonie (39,941 ha), Mts. Nebrodi (85,859 ha), Alcantara (1,927 ha) and Mts. Sicani (43,687 ha). In addition to these protected areas, there are several natural reserves (73) for a total 73,374 ha of protected area plus 238 SCIs (Sites of Community Importance) recognized within the Natura 2000 network of Sicily.
Crete is the fifth largest island in the Mediterranean Basin and is located in the southernmost part of Greece. It has a maximum length of about 250 km, 56 km maximum width and total area of 8,700 km2 including 200 small islands and islets around it. The island is generally characterized as mountainous. The proximity of the high mountains to the sea is characterized by large deep gorges, accommodating unique habitats.
According to the latest update, the flora of Crete comprises 1742 native species representing 623 genera and 128 families with ~10% of the taxa being endemic to the island. The floristic region of Crete - Karpathos is the most important center of endemism in Greece since according to recent data it is characterized by the highest rate of endemism.
Habitats rich in endemic species in Crete are the cliffs, gorges and areas of high altitude above 1,500 m a.s.l. However, the habitats in the gorges are more stable and not currently receiving intense pressure from human activities. In areas that are not characterized as rich in endemic plant species, such as lowland and upland areas, intensive agriculture has expanded, especially the cultivation of olive trees and greenhouse crops, thereby increasing the use of herbicides, pesticides and fertilizers and abandoning traditional terracing.
According to the Red Data Book of Rare and Threatened Plants of Greece (Phitos et al., 1995; Phitos et al., 2009), 110 plant taxa of Crete are considered threatened at national level.
Cyprus is the third largest island in the Mediterranean with an area of 9,251 km2. The island is divided into three geomorphological zones, the Troodos Range, the Pentadaktylos Range and the Mesaoria plain. The climate of Cyprus is typically Mediterranean with relatively short, mild and humid winters, long hot, dry summers and short autumn and spring seasons. The average annual rainfall is about 480 mm and ranges from 300 mm in the central plain and the south-eastern parts of the island up to 1,100 mm at the top of the Troodos range and 550 mm at the top of Pentadaktylos. The variation in rainfall is not only regional but annual and often two and even three-year consecutive droughts are observed. The average maximum temperature in July and August ranges between 29oC on the central plain and 22oC on the Troodos mountains.
The geomorphology of the island, the great variation in climatic conditions, its location between the three continents (Europe, Africa and Asia), along with 10,000 years of human presence, yielded a flora and fauna of great diversity and richness. Natural vegetation is made up primarily of extensive, natural pine forests, evergreen, sclerophyllous shrubs (maquis) and phrygana, while other vegetation types occupy more specialized habitats like riverine vegetation along streams, chasmophytes on cliffs, hygrophilous vegetation in water flooded sites etc. Concerning the terrestrial ecosystems, 41 habitat types are known so far to exist on the island, 11 of which are priority habitat types, according to the Habitats Directive of the European Union, including 4 endemic habitat types: Serpentinophilous grasslands of Cyprus (62B0*), Peat grasslands of Troodos (6460), Scrub and low forest vegetation of Quercus alnifolia (9390*) and Cedrus brevifolia forests (9590*).The percentage of Cyprus endemism regarding plants , is among the highest in Europe. The flora of Cyprus comprises about 1633 indigenous species and subspecies. The endemic flora of Cyprus includes 142 endemic taxa (species and subspecies) which consists the 8.7% of the native flora of Cyprus. Concerning the protection status, 46 plant taxa are characterised as critically endangered, 64 as endangered, 128 as vulnerable while 15 as near threatened based on the Red Data Book of the flora of Cyprus.