Taverna, A.; De Aranzamendi, M. C.; Maggioni, T.; Alurralde, G.; Turon, X.; Tatián, M. (2021). Morphology, genetics, and historical records support the synonymy of two ascidian species and suggest their spread throughout areas of the Southern Hemisphere. Invertebrate Systematics. 35: 675–687.
Taverna, A.; De Aranzamendi, M. C.; Maggioni, T.; Alurralde, G.; Turon, X.; Tatián, M.
2021
Morphology, genetics, and historical records support the synonymy of two ascidian species and suggest their spread throughout areas of the Southern Hemisphere
Invertebrate Systematics
35: 675–687
Publication
Taxonomic uncertainties and the lack of ecological knowledge can hinder the correct identification and the
assignment of biogeographic status of marine species. The ascidian Asterocarpa humilis (Heller, 1878), originally
described from New Zealand, has a broad distribution in shallow temperate areas of the Southern Hemisphere, having
recently colonised areas of the Northern Hemisphere. A closely related species, Cnemidocarpa robinsoni Hartmeyer,
1916, has been reported in the South-Eastern Pacific and the South-Western Atlantic, and several authors considered it a
junior synonym of A. humilis. We gathered for the first time morphological and genetic data from specimens from
distant areas. We studied the morphology of specimens collected at seven locations of South America. We also reexamined specimens from museum collections and revised the available literature on these species. Genetic data were
obtained from specimens from Argentina and compared with available sequences of A. humilis from Chile, New
Zealand, England and France. Morphological and genetic analyses showed that all compared specimens were
conspecific. Furthermore, specimens from different continents shared haplotypes and exhibited low genetic
distance among them. These results, the biological characteristics of this ascidian, and its longstanding presence in
different habitats from disjoint areas, allow us to question its native range. We support the idea that A. humilis is a
cryptogenic and neocosmopolitan species that has been transported by maritime traffic through the Southern
Hemisphere, revealing frequent processes of exchange through this wide area for more than a century, with
presumably associated alterations in the marine biota
