Molecular and morphological characterization of Laurencia intricataand Laurenciella mayaimii sp. nov. (Ceramiales, Rhodophyta) in South Florida, USA

Abstract:Morphological characterization, together with phylogenetic and DNA barcoding analyses on the basis of rbcL and COI-5P, conducted on some species of the Laurenciacomplex in South Florida confirmed the occurrence of Laurencia intricataand supported the presence and recognition of Laurenciellain the United States. Samples of L. intricatafrom Florida grouped with full support with the species from the type locality (Antilles). The intraspecific divergence within the L. intricataclade ranged from 0.0% to 1.3%; the samples from Florida diverged by only 0.06% to 0.20%, the sample from Mexico (EF658643 – Puerto Morelos, Quintana Roo) being the most divergent. The two new species of Laurenciellafrom Florida, La. mayaimiiand La. sp., formed an assemblage with La. marilzaewith full support, and the interspecific divergence was high for both molecular markers. Laurenciella mayaimiiis characterized mainly by its brownish-yellow main axis and cylindrical, alternate to subopposite branchlets, anastomoses between branches in the basal portions, and a single ‘corps en cerise’ present in each cortical cell and in trichoblasts. In addition, the walls of the cortical cells near the apices project, and lenticular thickenings are absent. The finding of Laurenciellain Biscayne Bay and Key Largo, South Florida expands its geographic distribution to western Atlantic lower subtropical waters.