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254 CALOGERO MUSCARELLA & ALESSANDRO BARAGONA

by relating the number of endemic species with the due to the sea depth in this coastal area), so that
area of the islands (Linear function model data: y even the colonization of scarcely vagile insects, as
=0.1608x + 8.9845; R = 0.3209; Pearson correlation the Tenebrionids, was made easier in these periods
index r = 0.54, see figure 8). (Fattorini, 2001). This way, species belonging to
Also, no relations seem to exist between the groups with a high tendency to speciation have had
number of endemic species and the geological struc- the possibility to reach the Aeolian islands and
ture of the islands (volcanic or sedimentary). Alicudi rapidly differentiate (Fattorini, 2011). This might
and Favignana, for instance, show the same number be the case of the disderid spiders, present in Lipari
of endemic taxa (6) but they are characterised by a with two endemic taxa - Harpactea aeoliensis
profoundly different lithology (see figure 6). Alicata, 1973 and Dysdera flagellifera aeoliensis
The complex paleogeographic history (see fur- Alicata, 1973 (Alicata, 1973); of the Curculionid
ther on) of the circum-sicilian islands, together with Beetles Otiorhynchus (Arammichnus) meligunensis
the dispersive features typical of every taxa, seem Magnano, 1992 and Pseudomeira aeolica Bellò,
to have been the most incisive factors determining Pesarini et Pierotti, 1997; of the Blattaria, present
the endemic population, and it does not seem pos- with three exclusive species (Ectobius aeoliensis
sible to hypothesize a unique colonisation and spe- Failla et Messina, 1974, E. filicensis Failla et Mess-
ciation model. Quite certainly, the different islands ina, 1974 ed E. parvosacculatus Failla et Messina,
(or at least the different archipelagoes), have had 1974) or of the gastropods of the Oxychilus type
different population means, whose vicariantist and Fitzinger, 1833, O. (Hyalocornea) alicurensis (Ben-
dispersalist models overlap. oit, 1857) of Alicudi and O. (Oxychilus) lagrecai
Giusti, 1973 of Filicudi. A likely hypothesis to ex-
Considerations on the endemic populations plain the genesis of some endemic species recon-
and paleogeography of the circum-sicilian nects to the high degree of environmental instability
islands typical of the Aeolian islands: continuous eruptions
allegedly determined the nullification of the present
Aeolian Archipelago fauna, repeatedly causing “bottleneck” effects, trig-
gering and quickening the birth of many of the en-
The Aeolian Islands are of relatively recent demic species present on these islands (Lo Cascio
formation: the most reliable radiometric dating & Navarra, 2003; Fattorini, 2009; Lo Cascio &
estimate that the archipelago formed approximately Sparacio, 2010). This might as well be the origin of
1.3 million years ago (in reference to the disap- some taxa such as Anoxia (Mesanoxia) matutinalis
peared apparatuses), while the most ancient rocks moltonii Sabatinelli, 1976, exclusive of Vulcano but
above sea level, present in Filicudi, date back to present with the nominal subspecies in the nearby
about 600,000 years ago (De Rosa et al., 2004; Lipari and Salina, Anthaxia (Haplantaxia) flaviae
Lucchi et al., 2013). They are separate from Sicily Lo Cascio et Sparacio, 2010 known for Panarea,
by a sea area which is up to 2000 m. deep and have Salina and Lipari but sympatric in the latter with the
always been isolated, even during the marine re- akin A. (Haplantaxia) scutellaris Genè, 1839 prob-
gressions in Pleistocene. Considering the relatively ably for a process of “double invasion” (Lo Cascio
young age of the archipelago, the high number of & Sparacio, 2010) and especially the Lacertid Podar-
endemic species found today (30) and its relative cis raffoneae (Mertens, 1952) and its subspecies. In
faunistic richness are surprising (cf. Lo Cascio & particular, for P. raffoneae, it would be otherwise
Navarra, 2003). Based on this interpretative model, difficult to explain the supposed “antiquity”, con-
the entire Aeolian fauna should be of recent ac- sidering that the molecular clocks that have been
quisition as entirely formed by propagules of high used for the datations confer it an age between 2
vagility species which rapidly differentiated on the and 13 million years, well before the formation of
spot thanks to the well known phenomena of the the “present” Aeolian islands (see Lo Cascio &
“bottleneck” and the “founder effect”. We should Navarra, 2003). Its current distribution, limited to
as well consider that during the phases of marine a few peripheral islets and Vulcano, is interpreted
regression the distance between Sicily and these is- as relictual in the field of an original area which
lands was undoubtedly shorter (though not annulled probably involved the whole archipelago; the most