XVI International Botanical Congess

Despite a recent body of literature, the species of Gracilaria recognised for the Gulf of Mexico are still incompletely characterised, misidentified, and species limits not well defined. We will discuss whether taxa said to belong to a single species across various biogeographic realms (Gulf of Mexico, western Atlantic, Caribbean) encompass indeed a single species, various ecotypes which are in the process of speciation, or instead new taxonomic entities which have already speciated. Our new species concepts are based on phylogenies inferred from sequence analysis of chloroplast-encoded rbcL, and on morphological evidence. Our results indicate the need to resurrect older, validly published names currently placed in synonymy under other species of Gracilaria, and to describe new species.