OLMSTEAD, RICHARD1* and DIANE FERGUSON2. 1Department of Botany, University of Washington, Seattle, WA 98195; 2Dept of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803. - A molecular phylogeny of the Boraginaceae/Hydrophyllaceae.
We conducted a molecular phylogenetic study of the Boraginaceae and
Hydrophyllaceae using the chloroplast genes rbcL and ndhF and
including 90 species previously assigned to the two families. Results
indicate that most of the taxa assigned to these families together
form a monophyletic group, but that neither of the two families, as
traditionally circumscribed, are monophyletic. Hydrolea
(Hydrophyllaceae) and Pteleocarpa (Boraginaceae) do not belong
in this group and are better placed elsewhere. Two major clades are
identified. The first major group includes the predominantly temperate
herbaceous subfamily Boraginoideae and the genus Codon
(Hydrophyllaceae; S. Africa). The other major monophyletic group
includes clades that correspond roughly to subfamilies Cordioideae,
Ehretioideae, and Heliotropoideae of Boraginaceae and tribes Nameae
and Hydrophylleae/Phacelieae of Hydrophyllaceae. Within this second
clade, the predominantly woody and tropical members of Boraginaceae
(Cordioideae, Ehretioideae, and Heliotropoideae) are monophyletic and
these are sister to tribe Nameae, which also contains the only woody
and tropical members of Hydrophyllaceae (along with other temperate
species). Pholisma, representing the small parasitic plant
family, Lennoaceae in our study, is sister to Tiquilia
(Ehretioideae), with which it co-occurs in the deserts of North
America. The primary characteristic that distinguishes Boraginaceae
from Hydrophyllaceae is the reduced number of ovules (2 per carpel).
The most parsimonious interpretation of this character on our tree
requires two independent reductions in ovule number, once in the
ancestor of the Boraginoideae (with the characteristic nutlet fruits)
and once in the ancestor of the tropical, woody clade (mostly
drupes).
Key words: Boraginaceae, Hydrophyllaceae, Lennoaceae, Solanales