Page 3 - Mannino_Balistreri_2017

Flora Mediterranea 27 — 2017 223

species is crucial for planning effective management and conservation strategies, the aim
of the present paper is to offer an updated overview of the distribution of invasive
Caulerpa specific and infraspecific taxa in Sicily and in circum-Sicilian Islands.

Materials and methods

All the relevant publications and reports dealing with invasive Caulerpa taxa in Sicily
and in circum-Sicilian Islands, from their first record in the area and updated till 2016,
were searched and analysed, using standard databases and available libraries at the
University of Palermo and at the Institut Méditerranéen d’Océanologie (MIO) of
Marseille. In situ observations provided by the authors of the present paper were included,
as well as personal communications provided by skilled citizen scientists.
The successful establishment of each taxon was determined on the basis of published
and unpublished data. We considered species as established when the species
was either established in the wild with free-living, self-maintaining and self-perpetuating
populations, or recorded at least twice and spread over time and space. The most plausible
pathway of introduction was attributed according to the hierarchical classification pathway
adopted by the CBD (2014).

Results

Caulerpa cylindracea
Distribution (Table 1 and Fig. 1): since 1993 (first Italian record at Baia di San Panagia
and at the Island of Lampedusa), the number of Sicilian sites affected by Caulerpa cylin-
dracea has regularly increased and the alga has been steadily spreading, as indicated by
the numerous new sightings recently recorded, mainly on the eastern coast. In particular,
the number of new colonized sites has increased significantly from 2000 to 2007.
Currently, 90% of areas colonized by C. cylindracea are located along the eastern and
north-western coasts of Sicily.
Colonisation level: the level of colonisation ranged from sparse individuals to patches
(ranging from 1 to 25 mq) and meadows (ranging from 150 mq to 1 ha) whereas the sub-
stratum cover (%) ranged from 5 to 100%.
Habitat (Fig. 2A, 3A, 3B): Caulerpa cylindracea is thriving under wide environmental
conditions: in marine and hyperaline habitats, from the surface down to 50 m depth (even
though the areas which were highly colonized ranged mainly from 0 to 20 m depth), on
sand, rock and mud (mainly on sand), on exposed and sheltered sites, under low and high
light conditions, in areas characterized by secondary volcanism phenomena (i.e. fumaroles
and hot springs, e.g. Aeolian Islands), in altered areas as well as in pristine and protected
areas (e.g. Marine Protected Areas and Natural Reserves).
Caulerpa cylindracea was found as an epibiont on different habitat-building species
like Mytilus galloprovincialis (Lamarck, 1819), the two reef-building species, the vermetid
Dendropoma cristatum (Biondi, 1859) and the polychaete Sabellaria alveolata (Linnaeus,
1767), but also on calcareous algae, sponges and corals. It was associated to both indige-