Molecular evidence forChondrophycus poiteauivar.gemmiferuscomb. etstat. nov. (Ceramiales, Rhodophyta) from the Mexican Caribbean Sea: implications for the taxonomy of theLaurenciacomplex

Molecular studies were carried out onChondrophycus gemmiferusandC. poiteaui(Rhodomelaceae) from the Mexican Caribbean Sea. These species are morphologically related, but differ mainly in the presence of the apiculate projection of epidermal cells near the apices of branches. Both species belong toChondrophycus,as indicated by the presence of two periaxial cells per axial segment and a 90° arrangement of tetrasporangia, but share characteristics withLaurenciaspecies (e.g., presence of secondary pit connections between adjacent epidermal cells). The phylogenetic position of these species was inferred by an analysis of chloroplast-encodedrbcL gene sequences of 21 taxa, using two members of the Rhodomelaceae and two of the Ceramiaceae as outgroups. The results corroborate the taxonomy of theLaurenciacomplex, which comprises the generaLaurencia, ChondrophycusandOsmundea, and indicate thatrbcL provides an adequate phylogenetic signal to study the intergeneric and interspecific relationships within the complex. In spite of this, relationships within the clade formed byC. gemmiferusandC. poiteauiwere not resolved by any analysis because of the low level of genetic variation between theirrbcL sequences (0.01–0.02%). On the basis of both molecular data and morphological similarities, we concluded thatC. gemmiferusshould be considered as a variety ofC. poiteauiand the following new combination is proposed:Chondrophycus poiteauivar.gemmiferus(Harvey) comb. etstat. nov.