Molecular assessment of the species of Gracilariaceae (Gracilariales, Rhodophyta) from the Yucatan Peninsula, Mexico, including two new records for the Mexican Atlantic

Background. The Gracilariaceae is one of the most diverse and abundant families of marine red algae. Most species in this family exhibit high morphological variability and overlapping of characters. In the Yucatan Peninsula 30 species have been historically recorded, but the phylogenetic identity for many of them is still unknown. Questions: Is the current diversity of the family in the area overestimated? Studied species: Crassiphycus caudatus, C. corneus, C. usneoides, Gracilaria flabelliformis, G. hayi, G. cf isabellana, G. microcarpa, G. occidentalis, G. suzanneae, Gracilariopsis tenuifrons. Study site and dates: Campeche: km 33 carretera Champotón, Bahía Tortuga, Puente Xen Kan III, Punta Xen, Sabancuy, 2017, 2018; Yucatan: Puerto Sisal, Puerto Progreso, Puerto Chicxulub, Puerto Telchac, 2018; Quintana Roo: Playa 88, Xcalacoco, Punta Esmeralda, 2019. Methods. Phylogenetic analysis (with COI-5P and rbcL sequences), supported by DNA species delimitation methods, genetic distances and morphological comparisons, allowed us to molecularly identify the specimens collected. Results. The phylogenetic identity of 10 species of Gracilariaceae was confirmed, two of which are new records for the Mexican Atlantic: G. hayi and G. suzanneae. Conclusion. The study demonstrated that the molecular assessment has proved to be very useful for the diversity evaluation, thus, the future phylogenetic identifies for the rest of morphospecies recorded in the area will allow a better approximation of Gracilariaceae diversity species.