NEVES, SUSANA S.1* and MARK F. WATSON2. 1Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; 2Royal Botanic Garden Edinburgh, Inverleith Row, Edinburgh, EH3 5LR, UK. - Phylogeny of Bupleurum (Apiaceae) based on ITS sequence data.
Bupleurum L. (Apiaceae: Apioideae) is a genus of ca. 150
species with broad distribution in the N Hemisphere (except the S
African B. mundii), but with many species that are rare or
restricted to small areas. The genus is easily recognized within the
family because of its simple and entire leaves, but unusually includes
woody members as well as the more usual annual and perennials herbs.
Bupleurum has for long been regarded as a natural group but its
infrageneric classification has been problematic. Phylogenetic
relationships of the genus were investigated using sequences of the
internal transcribed spacers (ITS) of nuclear ribosomal DNA, from 32
species (35 taxa) representing all sections and subsections of the
genus. Phylogenies generated by maximum parsimony, maximum likelihood,
and neighbour joining methods show very similar topologies,
unequivocally demonstrating monophyly of Bupleurum and the division of
the genus into two major clades (100% bootstrap support in all
analyses). The most basal clade is formed by all the species of the
genus with pinnate-reticulate veined leaves, and surprisingly also
includes B. rigidum, which itself has a unique type of leaf venation.
The other major clade comprises most of the species studied, all of
which have ± parallel-veined leaves. These results do not agree with
any previous classifications of the genus. Relationships within the
major clades are not fully resolved, and a larger sampling and further
data from other gene regions is required. Nevertheless, three other
strongly supported clades were identified; one of these clades
correspond to a group that includes all NW African endemic species,
and the low nucleotide variation in this group suggests a recent
radiation. The S African B. mundii seems to be a neoendemic
closely related to B. falcatum, an Eurasian species.
Key words: Apiaceae, Apioideae, Bupleurum, ITS nrDNA, molecular phylogeny