Molecular phylogeny of a rare New Zealand species of Lepidium (Brassicaceae)

Endemic to New Zealand, Lepidium sisymbroides, L. tenuicaule, and L. naufragorum are the three species used in this study. The goal of this project was to understand the phylogenetic placement of these relatives of the model plant Arabidopsis thaliana, including the only dioecious member of the Brassicaceae (L. sisymbrioides), and its close hermaphroditic relatives, L. tenuicaule and L naufragorum. An additional goal was to test whether these endangered New Zealand species belong to a monophyletic group. For that purpose we sequenced an intron of the floral transcription factor PISTILLATA (PI), a gene responsible for making petals and stamens. We used the intron to build a molecular phylogeny that places the three species studied within the larger Lepidium phylogeny as a first step towards understanding the evolution of dioecy in this flowering plant. Sequences were aligned and a phylogenetic tree was obtained using other published Lepidium species as an out-group. These results will advance the study of the evolution of separate sexes from hermaphroditism in plants, while making use of the tools available in the related model system.