HALL, JOCELYN C.* AND KENNETH J. SYTSMA. Department of Botany, University of Wisconsin, Madison, WI 53706. - Solving the riddle of Californian Cuisine: phylogenetic relationships of capers and mustards.
The pantropical family Capparaceae comprises approximately 40 genera
and 800 species. Capparaceae are well suited for systematic and
evolutionary inquiries. Not only are Capparaceae in need of
cladistically based phylogenetic hypotheses, but the diversity of
floral form exhibited by the group make the family a model system to
examine evolution of floral forms. It has been almost universally
agreed that Capparaceae have a very close phylogenetic relationship
with Brassicaceae, including the model species Arabidopsis
thaliana. Recent morphological and molecular analyses indicate
that Cleome (Capparaceae) are more closely related to Brassicaceae
than to other Capparaceae. However these studies have sampled a
maximum of four taxa from Capparaceae and typically have used only
two. The goal of this study was to clarify the relationships between
these two families by using evidence from DNA sequences of two regions
of the chloroplast, ndhF and trnL-trnF, and by
increasing sampling of Capparaceae to include most traditionally
circumscribed groups. We sampled over 10 genera of Capparaceae, 10
species of Brassicaceae, and outgroups chosen from previous analyses
of Capparales. Three monophyletic groups were supported:
Brassicaceae, Cleomoideae, and Capparoideae, the last two clades
corresponding to subfamilies of Capparaceae. Within the Capparaceae,
Capparis is paraphyletic. This is not surprising given that
more than one-half of the species of this family are placed in two
genera, Capparis and Cleome; suggesting that plants with
extreme morphological traits have been segregated out. Surprisingly,
the genus Forchhammeria (Capparaceae) appears to be either
sister to the rest of the Capparaceae and Brassicaceae clade or sister
to other families in the Capparales such as Pentadiplandraceae. The
chloroplast DNA phylogeny is used to assess floral character evolution
within Capparaceae and Brassicaceae. New nomenclatural possibilities
of naming Brassicaceae and Capparaceae will be evaluated based on
these data.
Key words: Arabidopsis , Brassicaceae, Capparaceae, chloroplast DNA, phylogenetics