Hidden diversity in Antarctica: Molecular and morphological evidence of two different species within one of the most conspicuous ascidian species

RUIZ, MICAELA B.; TAVERNA, ANABELA; SERVETTO, NATALIA; HELD, CHRISTOPH; SAHADE, RICARDO

Ecology and Evolution

John Wiley & Sons Ltd.

Año: 2020

2045-7758

The Southern Ocean is one of the most isolated marine ecosystems, characterized byhigh levels of endemism, diversity, and biomass. Ascidians are among the dominantgroups in Antarctic benthic assemblages; thus, recording the evolutionary patternsof this group is crucial to improve our current understanding of the assembly of thispolar ocean. We studied the genetic variation within Cnemidocarpa verrucosa sensulato, one of the most widely distributed abundant and studied ascidian species inAntarctica. Using a mitochondrial and a nuclear gene (COI and 18S), the phylogeography of fifteen populations distributed along the West Antarctic Peninsula andBurdwood Bank/MPA Namuncurá (South American shelf) was characterized, wherethe distribution of the genetic distance suggested the existence of, at least, two species within nominal C. verrucosa. When reevaluating morphological traits to distinguish between genetically defined species, the presence of a basal disk in one ofthe genotypes could be a diagnostic morphological trait to differentiate the species.These results are surprising due to the large research that has been carried out withthe conspicuous C. verrucosa with no differentiation between species. Furthermore,it provides important tools to distinguish species in the field and laboratory. Butalso, these results give new insights into patterns of differentiation between closelyrelated species that are distributed in sympatry, where the permeability of speciesboundaries still needs to be well understood.