Molecular analyses reveal a misidentification of <i>Gracilaria parvispora</i><scp>Abbott</scp> 1985 (<scp>Gracilariales, Rhodophyta</scp>) in the southern <scp>Mexican Pacific</scp> and the proposal of <i>Gracilaria huavensis</i> sp. nov.

SUMMARY Cylindrical red algae of the genus Gracilaria from the coastal lagoons of the Southern Mexican Pacific are described as a new species, G. huavensis sp. nov. based on rbc L and COI‐5P sequence analyses and detailed morphological, anatomical, and reproductive characteristics. This species typically grows in the intertidal and subtidal in brackish lagoons in the Southern Mexican Pacific. It is characterized by its percurrent cylindrical thalli with one to three orders of ramification with acute unilateral branchlets. Spermatangial conceptacles are of the textorii‐type. Cystocarps are spherical and possess numerous nutritive filaments at lateral and basal positions in the cystocarp cavity. Gracilaria huavensis is morphologically like G. parvispora but differs genetically. This species has been typically misidentified as G. parvispora but the clades formed by the Southern Mexican lagoons specimens for both markers were clearly separated from the G. parvispora sequences from Hawaii, Japan, South Korea, and Baja California Sur. Genetic distances between the Southern Mexican Pacific specimens and G. parvispora sequences were 1–1.6% in rbc L and 2.5–2.7% in COI‐5P. The morphological similarity between both species is the main cause of misidentifications. The occurrence of Asiatic G. parvispora in the Southern Mexican Pacific was not confirmed in this study, highlighting the need for molecular confirmation of species with problematic taxonomy.