Abstract
We discovered an unknown taxon of Cardamine (Brassicaceae) in Gifu Prefecture, located in the central part of Honshu Island, Japan. To elucidate the identity of this taxon, we constructed a highly resolved phylogeny of 19 species of Cardamine using multiplex inter-simple sequence repeat genotyping by sequencing (MIG-seq). The phylogenetic analysis revealed that the unknown taxon is closely related to C. schinziana O.E.Schulz and C. yezoensis Maxim., which are distributed to Hokkaido Island. This taxon is morphologically more similar to C. schinziana in being a small perennial with a glabrous plant body and in having 2–7 pairs of lateral leaflets with a shallow notch only on the lower margin. However, it is distinguishable from C. schinziana by its slender, terete stems up to 17 cm tall (vs. thicker, angular stems 20–50 cm tall), smaller leaves less than 6 cm long (vs. those reaching 10 cm or longer), leaflets with distinct petiolules up to 1–2 mm long (vs. those without distinct petiolules), and short rhizomes (vs. long, prostrating rhizomes). Based on this molecular evidence and morphological observations, we describe Cardamine neoensis Yahara, sp. nov.
