Laurencia natalensis (Ceramiales, Rhodophyta): a new record for the Atlantic Ocean

Abstract

We report for first time the species Laurencia natalensis for the Atlantic Ocean based on collections made in Venezuela. Once thought to be restricted to the Indian Ocean, the presence of this species is confirmed in this study by phylogenetic analyses using the plastid-encoded large subunit ribulose-bisphosphate carboxylase/oxygenase gene (rbcL). Sequences of the cytochrome C oxidase subunit I (COI) barcode region were obtained for additional support of taxonomic placement. In the rbcL phylogenetic analyses, a well-supported clade was recovered unequivocally placing our specimen as conspecific to L. natalensis from the east coast of South Africa. The barcode region (COI) sequences from Venezuela also clustered with the one obtained from L. natalensis from KwaZulu-Natal. In pairwise comparison of both markers, African and Venezuelan species diverged within the intraspecific variation recorded for Laurencia sensu stricto species. The Venezuelan specimens showed a distinctive combination of anatomical features shared with African specimens that aided in the species determination. However, sterile and immature sporophytic plants of Laurencia natalensis from Venezuela are morphologically variable; particularly sterile plants showed overall anatomical differences in habit when compared with African species. This finding raises the possibility that L. natalensis have been overlooked and probably confused in the field with other species of the Laurencia sensu stricto group.