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common in plants (LINHART & GRANT 1996) and local speciation associated with several
different types of evolutionary processes, such as hybridization, polyploidisation, inbreeding
and reticulate evolution also contribute to the evolution of endemic species throughout the
Mediterranean basin (THOMPSON 2005). In this framework, Sicily makes no exception. This
is the case, for instance, of many Sicilian endemites belonging to the genera Anthemis (GUA-
RINO et al. 2013), Brassica (RAIMONDO & GERACI 2002; BRULLO et al. 2013; SCIAN-
DRELLO et al. 2013), Centaurea (BANCHEVA et al., 2006, 2011), Helichrysum (IAMONICO
et al. 2016; MAGGIO et al. 2016), Quercus (BRULLO et al. 1999), etc.
Moreover, in the Sicilian mosaic landscape, where environmental gradients vary strongly
in space, localised floristic differentiation could represent an important driver not only for
the allopatric and sympatric speciation, but also for the local genetic differentiation of plant
lineages and for the overall plant species richness of the island, as well. The long-lasting
human history deeply affected these natural patterns and trends, by means of induced isola-
tion through habitat fragmentation, species migrations and the consequent set up of new spe-
cies assemblages.
Purpose of this paper is to review the potential significance of isolation and ecological dif-
ferentiation for the local floristic diversity and the evolution of narrow endemism in the Sici-
lian flora. In particular, we will focus on the following drivers of Sicilian floristic patterns and
related still open questions: 1. Geographical segregation and age of the Sicilian terrains; 2.
Climate variability and heterogeneity; 3. Geological patchiness; 4. Human influence on habi-
tat fragmentation.
Taxonomic nomenclature follows the second edition of the Flora of Italy (PIGNATTI et al.
2017-2018); syntaxonomic nomenclature follows the most recent syntaxonomic list of Sicily
(GUARINO et al. 2017).

1. Geographical segregation and age of the Sicilian terrains

With the exception of the NE corner of Sicily (Peloritani Mts.), which is a fragment of the
Iberian Margin shifted towards SE during the Alpine orogeny (SCIANDRELLO et al. 2015),
and of the SE corner of Sicily (Hyblaean Plateau), which is a fragment of the African plate
isostatically raised and shifted towards NW (BRULLO et al. 2011), all the rest of the island
was under water during lower Pliocene, i.e. between 5.3 and 3.6 million years ago (hereinafter
abbreviated with Ma). This is true even for the highest peaks of Madonie and Nebrodi Mts.,
now reaching nearly 2000 m a.s.l. (CATALANO et al. 2013), as well as for the single most rele-
vant landmark of the island, i.e. Mt. Etna (currently standing 3329 m a.s.l.), whose geological
history begun just 570 thousand years ago (BRANCA et al. 2008).
So far, this geological evidence has not been sufficiently considered by the scholars of the
Sicilian flora. Before the Pliocenic submersion stage some localised areas might have experi-
enced emersion, not only during the Messinian salinity crisis (c. 5.6 to 5.3 Ma) but several
times during Palaeogene and even during Mesozoic, as testified by several sedimentary suc-
cessions and continental erosion surfaces on the Panormide, Trapanese, Saccense, Ibleo-Pela-
gian carbonatic platforms, corresponding to shallow waters basins, where slight sea level
oscillations could give rise to emerged areas (CATALANO 2004).
It is likely that during upper Pliocene wider areas were emerged northwards (i.e. near Cor-
sican-Sardinian microplate) and southwestwards (i.e. near Tunisia), and that they went under-
water during the opening of the Tyrrhenian sea (ROSENBAUM & LISTER 2004). This hypo-
thesis still needs to be utterly confirmed by geological evidence but the occurrence of Tyr-

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