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Flora Mediterranea 27 — 2017 231

Fig. 5. Known sites of occurrence of Caulerpa taxifolia var. distichophylla in Sicily and circum-
Sicilian Islands (see Table 2 for the site codes).

Similar rapid spreads were observed in other Mediterranean areas, e.g. along the French
Mediterranean coasts and the south-eastern coast of Spain (Ruitton & al. 2005; Ruiz & al.
2011). However, even if C. cylindracea spread much faster and further than C. taxifolia it
didn’t generate the same public concern (Piazzi & al. 2005; Klein & Verlaque 2008;
Boudouresque & al. 2009).
The spread of C. cylindracea, considered established in Sicily and in circum-Sicilian
Islands, would probably result from the co-occurrence of extrinsic (i.e. current regime,
temperate climate and presence of vectors of secondary dispersal) and intrinsic (i.e. the
efficiency of its vegetative multiplication by cutting and propagules, the production of sec-
ondary metabolites) factors (Occhipinti-Ambrogi & al. 2011a, b; Gorbi & al. 2014). It has
been suggested that the invasion of the Mediterranean region by C. cylindracea might have
originated in the southern coast of Sic ily (Papini & al. 2013). Transport-stowaway is con-
sidered the plausible pathway of introduction for local specimens but also the main vector
of its spread.
The active mechanism of stolonisation allowed C. cylindracea to spread rapidly, form-
ing compact multilayered mats which trap sediment creating a relevant decrease of redox
potential underneath and negatively affecting the native assemblages (Piazzi & al. 2005;