Zoogeography of the ostracod genus Nannocandona (Podocopa) with description of two new species from Europe and East Asia

Candoninae is by far the most diverse ostracod group in subterranean habitats, with many genera which today have no surface water representatives. This subfamily is also peculiar because species tend to have restricted distributions regardless of habitat type, and, unlike other non-marine ostracod lineages, extremely rarely reproduce parthenogenetically. Nannocandona faba Ekman, 1914 is an exception, being originally described from Sweden, but then reported throughout the Holarctic. We study morphological variability of this species here, both based on old museum specimens and on freshly collected material. We propose that the name should only be restricted to the Swedish population, and we describe two new subterranean species: Nannocandona danielopoli n. sp. from Austria, and Nannocandona schornikovi n. sp. from South Korea and the Russian Far East. These descriptions allow us to evaluate records of N. faba in other parts of the Holarctic. A new map of the genus distribution is proposed, as well as a key to species identification. Parthenogenetic reproduction of Candoninae and their general ecology is also discussed.