Gracilaria suzannae sp. nov. (Gracilariales, Rhodophyta), a new flattened species from northeast Brazil based on morphological and molecular evidence

Abstract:

A new species of Gracilaria, G. suzannae sp. nov., is described on the basis of detailed morphological, anatomical and molecular evidence from recent collections from intertidal reefs of northeastern Brazil. Diagnostic features of the new species include: tufted and tough thalli with subdichotomous, alternate to irregular branches; some branches incurved, with discrete marginal teeth, giving thalli a dentate to lacerate appearance in the upper parts; an abrupt transition of cell size between cortical and medullary regions; spermatangial conceptacles of the textorii type; and mature cystocarps with inconspicuous inner pericarp and few tubular nutritive filaments, particularly in basal portions. Universal plastid amplicon sequences of G. suzannae formed a distinct group within the genus Gracilaria, with intraspecific divergence of 0.24%. In the rbcL analysis, G. suzannae was recovered as sister to a well-supported clade containing G. occidentalis from the United States, with interspecific divergence of 1.3%. Unlike our specimens, the thallus habit of G. occidentalis is repeatedly forked, with smooth margins and rounded apices. Furthermore, G. suzannae was phylogenetically positioned close to a major clade composed of Indo-Pacific flat species with lobed, spiny or denticulate margins, all of which diverged 1.1 to 4.8% from G. suzannae. Gracilaria suzannae becomes the 16th flat species of Gracilaria reported for Brazil.

Key Words::

• Algae
• Brazil
• Gracilaria
• Marine macroalgae
• Phylogeny
• rbcL
• Rhodophyta
• Seaweed
• Systematics
• Taxonomy
• UPA

ACKNOWLEDGEMENTS

The authors thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior for the PhD fellowship (23038.000077/2010-38) to LPS, as well as the Conselho Nacional de Desenvolvimento Científico e Tecnológico for the Productivity Fellowships (303915/2013-7) to MTF and (309658/2016-0) to CFDG. This work was partially supported by a research grant from Fundação de Amparo à Pesquisa de São Paulo (2012/18775-6). The authors are grateful to reviewers and editors who helped improve this manuscript with their suggestions.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/17-102.1.s1.