Phylogenetic position of the East Asian ostracod genus Undulacandona within Candonidae with description of four new species from subterranean waters of Korea

Family Candonidae is one of the most diverse freshwater ostracod groups in terms of number of taxa and ecological adaptations. The family is especially well represented in the subterranean waters around the world, with many species being short-range endemics. Here we describe four new species, Undulacandona koreanasp. nov., U. aeolussp. nov., U. andromedasp. nov. and U. cetussp. nov., from two localities in the central part of South Korea. One more species, Undulacandona sp., is briefly reported here, but not described because of the absence of adults. The mtCOI sequence obtained from Undulacandona sp. and its closest relative, U. koreana, supports a separate species status. Undulacandona Smith, 2011 was previously known only from two species from Japan. A peculiar looking Zenker organ, hemipenis, and uropodal ramus of the six Undulacandona suggest an isolated position in the family Candonidae. Here we use 28S and 18S rRNA to reconstruct phylogenetical relationships within candonid ostracods, but also between the three closely related families: Candonidae, Cyclocyprididae and Paracyprididae. We sample 30 species and use three methods to reconstruct the phylogenetic relationships: Bayesian inference, maximum likelihood and maximum parsimony. None of the methods and neither of the markers clearly resolve the interfamily relationships. However, the family Candonidae is always supported with highest bootstrap values and posterior probabilities, as is a sister relationship between Undulacandona and Cryptocandona Kaufmann, 1900. Our results also indicate the need for a revision of Paracyprididae, as well as the polyphyletic nature of the genus Fabaeformiscandona Krstic, 1972. We also recognize potential misidentifications on GenBank. Finally, we also provide a taxonomic key to Undulacandona species.