MEDITERRANEAN CAULERPA TAXIFOLIA AND C. MEXICANA (CHLOROPHYTA) ARE NOT CONSPECIFIC

Abstract

In 1984, Caulerpa taxifolia (Vahl) C. Agardh was reported along the coast of Monaco. Over the past decade it has spread along 60 km of the Mediterranean coastline and presently represents a potential risk to biodiversity. Several explanations have been advanced regarding the presence of C. taxifolia in the Mediterranean. One hypothesis maintains that the alga was introduced accidentally into the sea at Monaco, where it has been used as a decorative alga in aquaria. Caulerpa taxifolia has not been reported in earlier marine floras of the Mediterranean, and its sudden appearance has suggested that it may be a recent introduction. Another hypothesis proposes that C. taxifolia and Caulerpa mexicana Sonder ex Kützing are morphological variants of one another and hence conspecific taxa. Caulerpa mexicana has been found in the eastern Mediterranean since at least 1941. In order to establish the taxonomic identities of these taxa, individuals from five populations of C. taxifolia and four populations of C. mexicana were collected from within and outside of the Mediterranean. Comparative DNA sequence analysis of the nuclear ribosomal cistron, including the 3′‐end of the 18S, ITS1, 5.8S, and ITS2 regions, show clear phylogenetic separation of the two taxa using parsimony and maximum likelihood analyses. Separation is maintained whether the analyses are based on just the more conserved 18S data or just the fast‐ evolving spacers. The two species are thus not conspecific. For specimens of uncertain identity (i.e. taxifolia–mexicana intermediates), a PCR diagnostic amplification can easily be performed because the ITS1 in C. taxifolia is 36 nucleotides shorter than the ITS1 in C. mexicana. Whether or not C. taxifolia has been present for a longer period of time in the marine flora, either as a cryptic endemic species or as the result of one or more introductions, represents an additional hypothesis that will require identification of biogeographic populations from throughout the world, as well as a population‐level study of the Mediterranean region.

First record of <em>Caulerpa cylindracea</em> (Caulerpaceae, Chlorophyta) in Andalusia (Southern Spain)

“…More than 100 nuclear rDNA-ITS sequences from Caulerpa species are available in GenBank. Amongst these, four sequences of Caulerpa mexicana Sonder ex Kützing (AJ007815-18; Olsen & al., 1998) were selected as outgroups in all phylogenetic reconstructions and were aligned against 27 ITS1-5.8S-ITS2 sequences produced in this study and 40 publically available sequences to create a final dataset of 71 sequences (see Table 1 for sequence accession numbers). Alignments were optimized in MUSCLE (http://www.ebi.ac.uk/Tools/msa/muscle/), trimmed in BIOEDIT version 7.0.9.0 (Hall, 1999) and refined by eye.…”

“…racemosa Heron Island, Australia AJ297651 (Durand & al., 2002) 57 C. racemosa var. racemosa Balicasag Island, Philippines AJ297652 clone a, AJ297653 clone b (Durand & al., 2002) 58 C. mexicana Canary Islands, Spain AJ007816 (Olsen & al., 1998) 59 C. mexicana Florida, USA AJ007818 (Olsen & al., 1998) 60 C. mexicana Israel AJ007815 (Olsen & al., 1998) 61 C. mexicana Panamá AJ007817 (Olsen & al., 1998) *New accession numbers. (Verlaque & al., 2003), i.e.…”

On the identity and origin of the Mediterranean invasiveCaulerpa racemosa(Caulerpales, Chlorophyta)

“…The statistical robustness of nodes was ascertained by bootstrapping (Felsenstein, 1992) with 1000 iterations for NJ and MP and 100 iterations for ML. A set of published sequences of Caulerpa mexicana Sonder ex Ku¨tzing (Olsen et al, 1998) (Table 1) was used as the outgroup taxon.…”

Identity and origin of a slender Caulerpa taxifolia strain introduced into the Mediterranean Sea

“…The more notorious of the two is C. taxifolia , which became a dominant feature of the northwestern Mediterranean coastline (Meinesz et al 2001 ) after its apparently accidental release from the public aquarium in Monaco, where it was on display Hesse 1991 , Jousson et al 1998 ). Large meadows of C. taxifolia have been reported along the Mediterranean coastlines of France, northern Italy, Croatia, Sicily, Sardinia and the Balearic Islands (Jousson et al 1998, Olsen et al 1998, Meinesz et al 2001, although currently it seems in natural regression in many areas (e.g., Ive š a et al , Meinesz et al 2010.…”