Systematic relationships of New Zealand endemic Brassicaceae inferred fromnrDNA ITS sequence data

Phylogenetic relationships of New Zealand species of Brassicaceae belonging to the South Island endemic Ischnocarpus, Iti, Notothalspi, and Pachyclado n, and the indigenous Cardamine, Cheesemania, Lepidium, and Rorippa were st udied using nuclear ribosomal internal transcribed spacer sequences. Result s support a monophyletic Notothalaspi and suggest that species of this genu s are not closely related to Thlaspi. the genus to which Hooker provisional ly assigned N. australe. The cosmopolitan genus Cardamine is paraphyletic b y the inclusion of the monotypic genus Iti. The association of Iti with New Zealand Cardamine is of particular significance, as the relationships of t his monotypic genus have historically proven elusive. Cheesemania species, Ischnocarpus novae-zelandiae. and Pachycladon novae-zelandiae form a closel y related monophyletic group. The species of Lepidium form a monophyletic g roup, but the New Zealand species are not monophyletic indicating two possi ble dispersal events to New Zealand. Additionally. the tribes Arabidieae, L epidieae, and Sisymbrieae are polyphyletic. This study highlights the diffi culty of using traditional characters such as fruit type and cotyledon arra ngement to define the tribes of the Brassicaceae.