A new species of marine algae from the Mexican Atlantic based on morphology and molecular data: Gelidium rodrigueziae sp. nov. (Gelidiaceae, Rhodophyta)

The algae of the genus Gelidium can be found as frequent and abundant inhabitants in the rocky intertidal zone of the Mexican Atlantic. Six species of this genus have been reported in this region, but only Gelidium americanum has been confirmed with morphological and molecular tools, despite how important both tools have proven to be for the group. This research aimed to evaluate the Mexican specimens previously identified as Gelidium through morphological and molecular approaches, using rbcL and COI-5P markers. This study examined 20 specimens found living attached to the shell of a gastropod Stramonita rustica in the mid-high intertidal zone of the Mexican Atlantic and ten specimens found living on rocks. Phylogenetic analyses resolved these specimens to be an independent species closely related to G. gonzalezii, G. yangmeikengense, and G. indonesianum. Genetic distances and morphological information confirmed this. Gelidium rodrigueziae sp. nov. is described as a new species. It is distinguished from its related species by having a simpler branching pattern, a smaller number and size of medullary cells, and the smaller quantity and distribution of restricted internal rhizoid filaments around the medulla.