1 Systematic Relationships of Arabidopsis: A Molecular and Morphological Perspective

Abstract

Our rapidly expanding knowledge of the molecular and developmental biology of Arabidopsis thaliana is of fundamental importance to a better understanding of biological systems in crops and other plants. This knowledge will be particularly valuable in future examinations of evolutionary processes at the generic, specific, and population levels. To effectively utilize the knowledge gained from A. thaliana in an evolutionary context, information concerning its phylogenetic relationships is essential. However, despite the great utility of A. thaliana for comparative studies, remarkably little basic information is available concerning the systematics and evolution of the genus Arabidopsis and its relationships within the mustard family. The boundaries of the genus Arabidopsis are very poorly known, and the majority of species now assigned to the genus are not yet accessible for scientific study because of their restricted geographic distributions in remote mountainous areas of Asia. In the following sections, we summarize available information concerning the systematics and phylogenetic position of A. thaliana both from the standpoint of traditional morphologically based classifications and from new data from molecular comparisons. We review the geographic distribution and chromosome numbers of the other species currently placed in the genus Arabidopsis and the problematic nature of its delimitation and tribal placement in the Brassicaceae. We also present new information on the phylogenetic relationships of A. thaliana within the family obtained from sequence comparisons of the chloroplast rbcL gene and from preliminary analyses of restriction site data from the chloroplast genome.

SYSTEMATIC RELATIONSHIPS OF ARABIDOPSIS
Familial and Tribal Classification of Arabidopsis