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Ber. d. Reinh.-Tüxen-Ges. 30, 133-148. Hannover 2018

Sicily: the island that didn’t know to be an archipelago

– Riccardo Guarino, Palermo & Salvatore Pasta, Fribourg –

Abstract

Recent geological studies demonstrated that most of Sicily was still under water during
lower Pliocene, with the exception of the NE and the SE corners of the island (Peloritani Mts
and Hyblaean Plateau, respectively). This geological evidence, so far not considered suffi-
ciently by the scholars of the Sicilian flora, poses many still open questions on how and where
many ancient lineages and Palaeogene relicts, currently found on the island, managed to sur-
vive. Purpose of this paper is to review the potential significance of isolation and ecological
differentiation for the local floristic diversity and the evolution of narrow endemism in the
Sicilian flora. In particular, the following drivers of Sicilian floristic patterns are considered:
geographical segregation and age of the Sicilian terrains; climate variability and heterogenei-
ty; geological patchiness; human influence on habitat fragmentation.
Key words: Sicily, flora, biogeography.
Introduction
2
Sicily is the largest Mediterranean island, with an extension of nearly 26000 km . The Sici-
lian territory is predominantly hilly or mountainous: one fourth of the island is at more than
700 m a.s.l.; two thirds range between 300 and 700; one sixth below 300 m a.s.l. The geogra-
phical position of Sicily, its complex geological history and the high topographic diversity
make the island one of the most heterogeneous Mediterranean territories, under the geo-mor-
phologic, edaphic and climatic viewpoint. The island is widely recognized by botanists as one
of the main hot-spots of plant diversity in the Mediterranean basin (HEYWOOD 1995;
MÉDAIL & QUÉZEL 1997, 1999; MYERS et al. 2000; MÉDAIL & DIADEMA 2009). Its rich
flora counts approximately 3250 native species, 12.6% of which are endemites (BRULLO et
al. 2012), witnessing the complex paleogeographic history and physiographic settlement of
the island (NIMIS 1984, 1985). A striking feature of the Sicilian endemism is that the largest
majority (9.1%, according to RAIMONDO & SPADARO 2009) are narrow endemic species,
i.e., they have a distribution which is restricted to a single well-defined area within a small
part of the island (BRULLO et al. 1995; BONANNO & VENEZIANO 2016).
Many Sicilian endemites exhibit what has been termed a “schizo-endemic” pattern of dis-
tribution (FAVARGER & CONTANDRIOPOULOS 1961, CONTANDRIOPOULOS 1962). The
prevailing paradigm for the evolution of such endemic taxa relies on the assumption of diffe-
rentiation due to the fragmentation of the range of a widespread ancestral taxon to produce
endemic taxa in different parts of the original distribution (THOMPSON et al. 2005). For
instance, this is the case of the Sicilian taxa ascribed to the genera Armeria (AGUILAR et al.
1999), Asperula (BRULLO et al. 2009), Astragalus (NIMIS 1981), Campanula (BRULLO
1983), Pseudoscabiosa (CAPUTO & COZZOLINO 1994), Salix (BRULLO & SPAMPINATO
1988) and Trifolium (BRULLO et al. 2000), among the others.
However, in the case of vascular plants, phylogeographic breaks may develop also in the
absence of geographical or ecological barriers to gene flow: local genetic differentiation is

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