Page 1 - Mannino_Balistreri_2017

Fl. Medit. 27: 221-240
doi: 10.7320/FlMedit27.221
Version of Record published online on 13 November 2017

Anna Maria Mannino & Paolo Balistreri

An updated overview of invasive Caulerpa taxa in Sicily and circum-
Sicilian Islands, strategic zones within the NW Mediterranean Sea

Abstract
Mannino, A. M. & Balistreri, P.: An updated overview of invasive Caulerpa taxa in Sicily and
circum-Sicilian Islands, strategic zones within the NW Mediterranean Sea. — Fl. Medit. 27:
221-240. 2017. — ISSN: 1120-4052 printed, 2240-4538 online.
The spread dynamics of invasive Caulerpa taxa (i.e. Caulerpa cylindracea, C. taxifolia var. taxi-
folia and C. taxifolia var. distichophylla) in Sicily and circum-Sicilian Islands, based on relevant
publications, grey literature, unpublished data and in situ observations during the last 23 years, is
presented here and discussed. Their known distribution is mapped. New records are also reported.
Transport-stowaway is considered the most plausible vector of introduction of invasive Caulerpa
in the area. The three invasive taxa showed different spread dynamics. Caulerpa cylindracea and
C. taxifolia var. distichophylla, behaved as highly successful and fast-spreading taxa, i.e. as true
invasive taxa. On the contrary, C. taxifolia var. taxifolia did not behave like the others, remaining
limited to two small areas distant from each other. Due to their geographical position, Sicily and
circum-Sicilian Islands are particularly vulnerable to biological invasions and therefore they could
play an important role as receiver, transit and donor zone for alien species within the
Mediterranean Sea. The creation of permanent observatories and alarm systems in this area might
be an effective tool in the management of present and future introductions of alien species in the
Mediterranean Sea.
Key words: Caulerpa cylindracea, C. taxifolia, invasive species, Mediterranean basin.

Introduction

The Mediterranean Sea is an important hotspot for alien species (Rilov & Galil 2009;
Coll & al. 2010; Zenetos & al. 2012; Galil & al. 2015) which have almost reached a num-
ber of 1,000 (about 6% of the total flora and fauna) (Zenetos & al. 2012).
According to the definition adopted by the European Environmental Agency (2012), “an
alien species is an organism introduced outside its natural past or present distribution range
by human agency, either directly or indirectly.” Whereas species which have expanded their
range as a result of changing environmental conditions are not considered alien species.
Por (1978) coined the term “Lessepsian migration” to indicate the phenomenon of migra-
tion of Red Sea species into the Mediterranean Sea through the Suez Canal (opened in 1869).