Gelidiella papillosa sp. nov. (Gelidiellaceae, Rhodophyta) from Veracruz, Mexico, in the context of the worldwide distribution of G. acerosa

Abstract Gelidiella acerosa is a widely distributed species, with type locality in Yemen, whose morphology has been characterized by decumbent axes from which numerous abundantly branched erect axes emerge, pectinate, alternate or radial. Recent phylogenetic studies have revealed the presence of genetically independent groups throughout its distribution range. However, these groups cannot be described as independent since there are no sequences from the type locality that allow us to establish the genetic group to which the true G. acerosa belongs, generating a complex of cryptic species. In the present study, from COI-5P and rbc L sequence data, we detected six genetically differentiated groups, one of which is represented only by specimens from the Western Atlantic region. Given the allopatric pattern, it is possible to describe the Atlantic group as an independent species of the cryptic complex in the Indo-Pacific. Gelidiella papillosa sp. nov. shares several morphological features with other specimens previously identified as G. acerosa in other countries, like the appearance of the thallus, branching patterns, the presence of multiple superficial hairs on the branches or cell measurements. However, these characters have not been evaluated in detail among the different genetic groups within Gelidiella acerosa , consequently, G. papillosa can be supported only by its genetic independence and allopatric distribution.