DNA SEQUENCE DATA DEMONSTRATE THE POLYPHYLY OF THE GENUS CYSTOSEIRA AND OTHER SARGASSACEAE GENERA (PHAEOPHYCEAE)¹

Abstract

Phylogenetic relationships in the Sargassaceae were explored using three DNA markers, and the monophyly of its genera was challenged. Nineteen out of 24 currently recognized genera were sampled, representing 63 species. The variable mt23S-tRNA Val intergenic spacer could only be aligned within genera and could not be used to infer intergeneric relationships. The partial mt23S was also useful to delineate genera and was alignable at the family level but provided few informative characters. Analysis of mt23S DNA sequences together with chloroplastencoded psbA sequences resulted in a better resolved phylogeny. Hormophysa was the first genus to branch off within the Sargassaceae, followed by Myriodesma; then the three genera Caulocystis, Carpoglossum, and Scaberia in unresolved order; and then Acrocarpia. The other taxa studied here were divided over three major clades, but there was no branch support for the monophyly of two of these. The genera Bifurcaria, Cystoseira, Halidrys, and Sargassum appeared polyphyletic. The following taxonomic changes are proposed: a new genus Brassicophycus for Bifurcaria brassicaeformis (Kützing) E. S. Barton; reinstatement of the genus Sargassopsis for Sargassum decurrens (R. Brown ex Turner) C. Agardh; reinstatement of the genus Sirophysalis for Indo-Pacific Cystoseira trinodis (Forsskål) C. Agardh; reinstatement of the genus Polycladia for the western Indian Ocean species Cystoseira indica (Thivy et Doshi) Mairh, Cystoseira myrica (S. G. Gmelin) C. Agardh, and Acystis heinii Schiffner; and reinstatement of the genus Stephanocystis for the North Pacific Cystoseira species and Halidrys dioica N. L. Gardner. The European Cystoseira species should be split into three genera, but no name changes are proposed yet, because diagnostic characters were found only for the clade including the type species. Some evolutionary trends could be discerned from the mt23S + psbA phylogeny.

Decline and local extinction of Fucales in French Riviera: the harbinger of future extinctions?

“…The Mediterranean treatment of the genera Cystoseira and Sargassum differs according to the authors (Ribera et al, 1992;Gómez Garreta et al, 2000;Coll et al, 2010;Draisma et al, 2010;Cormaci et al, 2012;Rožić et al, 2012;Guiry & Guiry, 2014). The taxonomy of these genera is complex and progress will depend on molecular studies unravelling the relationships between the species, varieties and forms.…”

Taxonomy of Marine Macroalgae Used as Sources of Bioactive Compounds

“…Molecular data have become available only very recently for Cystoseira and related genera, and have revealed a very complex evolutionary scenario. Draisma et al ( 2010 ) showed that Cystoseira , as circumscribed morphologically, is polyphyletic, and this is also the case for other closely related genera such as Bifurcaria and Halidrys (hypothesis that had already been suggested by Harvey and Goff 2006 ) . For this reason these authors split Cystoseira in four different genera, reinstating Sirophysalis for the Indo-Pacifi c species Cystoseira trinodis , Polycladia for the western Indian Ocean species Cystoseira indica and Cystoseira myrica , and Stephanocystis for the North Pacifi c Cystoseira and Halidrys species.…”

“…Molecular data produced in recent studies have signifi cantly contributed to the understanding of the diversity and phylogenetic relationships in this genus. Draisma et al ( 2010 ) showed that Sargassum was polyphyletic and reinstated the genus Sargassopsis Trevisan (non Nizamuddin et al) for S. decurrens . Examining the diversity of Sargassum in the south Pacifi c, Mattio et al ( 2008 ) ; reassessed the status of numerous species, resolved several taxonomic incongruities, and provided an advanced revision of several sections.…”

“…For this reason these authors split Cystoseira in four different genera, reinstating Sirophysalis for the Indo-Pacifi c species Cystoseira trinodis , Polycladia for the western Indian Ocean species Cystoseira indica and Cystoseira myrica , and Stephanocystis for the North Pacifi c Cystoseira and Halidrys species. Draisma et al ( 2010 ) concluded that European Cystoseira will also need further study to discover diagnostic characters for different lineages. Many species of Cystoseira are very variable in morphology; for Mediterranean species, in particular, it is not uncommon to fi nd specimens with intermediate characteristics that are impossible to identify unambiguously on the basis of morphology.…”

Seasonal dynamics and annual production of <i>Cystoseira crinita</i> (Fucales: Ochrophyta)-dominated assemblages from the northwestern Mediterranean

“…extremely reduced tides, oligotrophy, relatively high salinity and a high mean summer temperature (Ros et al 1985), probably prevent the growth of kelp beds. The genus Cystoseira is present in the northern Atlantic Ocean and in the Mediterranean Sea (Draisma et al 2010), and it is especially diverse in the Mediterranean (ca. 50 species).…”