Two new flat species of Gracilaria (Gracilariales, Rhodophyta) from Brazil:: G-abyssalis sp nov and G-brasiliensis sp nov.

A recent survey of the Brazilian Gracilariaceae (Rhodophyta, Gracilariales) flora aided by molecular-based phylogenetic analyses and comparative morphological data revealed two unidentified flat species of Gracilaria described here: G. abyssalis sp. nov. and G. brasiliensis sp. nov. Gracilaria ablyssalis is a deep-water species characterized by a conspicuous holdfast; a long, branched, robust stipe; irregular to sympodial branching of the thallus occasional presence of midrib; and an extensive range of broad blade morphologies. Gracilaria brasiliensis is a shallow intertidal species characterized by an inconspicuous stipe (< 1 cm), regular dichotomously branched thalli, and narrow blades and rounded apices. DNA sequence analyses of the chloroplast-encoded rbcL-gene showed that flat species of Gracilaria in the western Atlantic belong to two distinct lineages. Maximum parsimony results placed G. brasiliensis as a member of the G. mammillaris clade with no support, while Bayesian results identified this species as a disntict new independent lineage. Furthermore, it was found that G. cuneata and G. curtissiae are recently diverged sister species and that rbcL phylogenetic distances among the morphologically distinct G. intermedia and G. yoneshigueana are quite small.