An African Royal Flush: five crowned nudibranch species (Nudibranchia: Polyceridae) recovered from temperate southern Africa using integrative taxonomy

The northeastern Atlantic species of nudibranch genus Polycera have received much attention in recent years, however southern African representatives remain to be further investigated. Here, we further examine the genus along the south and southwest coasts of southern Africa, combining molecular and morphological data. We describe three new species, Polycera namaquae sp. nov., Polycera enesithsaba sp. nov. and Polycera onomqhele sp. nov., in addition to the already documented P. capensis and P. hedgpethi. We demonstrate variation in external appearance within the species we examined, highlighting the importance of incorporating genetic data in species identification and descriptions. Molecular evidence supports the hypothesis that Polycera hedgpethi is introduced in South Africa, likely from the northeastern Pacific coast, while all other species share close relationships to species from the northeastern Atlantic with more biogeographical connections spanning hemispheres, rather than within. Recovered ranges of each species within southern Africa follow defined biogeographical boundaries, highlighting the importance of these diverse ecoregions in shaping marine biodiversity. Overall, this work suggests multiple vicariant events as drivers of diversification of the southern African and northeastern Atlantic coastal biota.