Shining disco: shedding light into the systematics of the family Discodorididae (Gastropoda: Nudibranchia)

Abstract The evolutionary relationships among genera within the nudibranch family Discodorididae remain poorly understood, with comprehensive molecular studies still largely absent. Discodoris, the most species-rich genus within this family, has historically represented a wastebasket taxon where species with ‘discodoridid’ morphology were placed. In this study, we present molecular data to evaluate the taxonomic classification of the family and to investigate potential (pseudo)cryptic diversity. Our molecular analyses comprised a multilocus phylogenetic analysis of 199 specimens, including 20 type species. The dataset included 142 specimens belonging to Discodorididae, 24 from Dorididae, and 33 outgroup taxa. A total of 52 specimens from 30 different species of Discodorididae, including six type taxa, were sequenced from the Mediterranean Sea, Eastern Atlantic Ocean, and Central and South America. Phylogenetic analyses recovered the monophyly of the family Discodorididae but including the doridid Aphelodoris, revealing evidence of hidden diversity in several genera such as Taringa, Tayuva, Paradoris, and Geitodoris. Our study unveiled the paraphyly of the genera Discodoris and Diaulula, which warrant a critical appraisal of their morphology. Overall, we provide relevant molecular information to infer the most complete phylogeny of Discodorididae to date and identify new questions for future studies.