Systematic revision of the speciose sea slug genusDoto(Heterobranchia: Nudibranchia) - from the Mediterranean to South America

The genusDotoOken, 1815 is, taxonomically, one of the most complex genera of nudibranchs due to the cryptic nature of its species, their small body size, and the homogeneity among their internal and external features. Here, an extensive molecular analysis of Mediterranean, Northeastern Atlantic, and South American specimens sheds light on the species-level taxonomy of the group. Our multilocus analyses include 171 specimens, 59 newly sequenced, corresponding to 20 species. Ten species are included in a molecular phylogeny for the first time, two being new species. Here, we provided detailed morphological and ecological descriptions of three Atlantic species, 11 Mediterranean, and one from the Pacific, complemented by live photographs evidencing their chromatic variation. The phylogenetic and species delimitation analyses suggest that coloration and external morphology often seem unreliable to differentiate among species. Molecular evidence corroborates and expands the geographical distribution ofDotospecies, some of which have never been included in molecular studies. The Mediterranean species currently recognized asD. coronata(Gmelin, 1791) andD. dunneiLemche, 1976 correspond toD. millbayanaLemche, 1976. Consequently, we suggest the junior synonymy withD. dunneisyn. nov.Nevertheless, we found evidence for a restricted distribution ofD. coronatain the western Mediterranean, coexisting in sympatry withD. cavernicolasp. nov.An additional new species from the Chilean Patagonia is also described asD. vrenifossorumsp. nov.Considering the present phylogenetic scenario, there is a highlighted need for further new morphological and genetic evidence, expanding the number of taxa and species to further unravel the taxonomy ofDoto.

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