Morphology, genetics, and historical records support the synonymy of two ascidian species and suggest their spread throughout areas of the Southern Hemisphere

Taxonomic uncertainties and the lack of ecological knowledge can hinder correct identification assignment biogeographic status marine species. The ascidian Asterocarpa humilis (Heller, 1878), originally described from New Zealand, has a broad distribution in shallow temperate areas Southern Hemisphere, having recently colonised Northern Hemisphere. A closely related species, Cnemidocarpa robinsoni Hartmeyer, 1916, been reported South-Eastern Pacific South-Western Atlantic, several authors considered it junior synonym A. humilis. We gathered for first time morphological genetic data specimens distant areas. studied morphology collected at seven locations South America. also re-examined museum collections revised available literature on these Genetic were obtained Argentina compared with sequences Chile, England France. Morphological analyses showed that all conspecific. Furthermore, different continents shared haplotypes exhibited low distance among them. These results, biological characteristics this ascidian, its longstanding presence habitats disjoint areas, allow us to question native range. support idea is cryptogenic neocosmopolitan species transported by maritime traffic through revealing frequent processes exchange wide area more than century, presumably associated alterations biota.