Phylogenetic Position and Generic Limits of Arabidopsis (Brassicaceae) Based on Sequences of Nuclear Ribosomal DNA

The primary goals of this study were to assess the generic limits and monophyly of Arabidopsis and to investigate its relationships to related taxa in the family Brassicaceae. Sequences of the internal transcribed spacer region (ITS-1 and ITS-2) of nuclear ribosomal DNA, including 5.8S rDNA, were used in maximum parsimony analyses to construct phylogenetic trees. An attempt was made to include all species currently or recently included in Arabidopsis, as well as species suggested to be close relatives. Our findings show that Arabidopsis, as traditionally recognized, is polyphyletic. The genus, as recircumscribed based on our results, (1) now includes species previously placed in Cardaminopsis and Hylandra as well as three species of Arabis and (2) excludes species now placed in Crucihimalaya, Beringia, Olimarabidopsis, Pseudoarabidopsis, and Ianhedgea.