WEEKS, ANDREA* and BERYL B. SIMPSON. The University of Texas at Austin and the Plant Resources Center, Austin, Texas 78712. - The presence of Commiphora (Burseraceae) in the New World is confirmed.
The genus Commiphora (Burseraceae) comprises over 200 species
of trees native to the seasonally-dry tropics of Africa and India. The
taxonomic distinction between this genus and its putative sister,
Bursera, a genus of ~100 species with an entirely Neotropical
distribution, is based on one petal aestivation character. On the
basis of this and other morphological and ecological similarities,
several authors have hypothesized that these two genera may form a
paraphyletic grade. Here we present a preliminary sectional phylogeny
of Commiphora based on sequences of the nuclear rDNA external
transcribed spacer region (ETS) including representative sampling of
Bursera and Boswellia. Additionally, we test the
phylogenetic placement of three species of Bursera recently
transferred to Commiphora: B. inaguensis, B.
leptophloeos, and B. tecomaca. While multiple copies of ETS
exist within each individual, they coalesce at the species-level and,
therefore, are appropriate for phylogenetic reconstruction at the
supraspecific level. Contrary to the details of previous hypotheses,
Commiphora is sister to Bursera sect. Bursera and
not to Bursera sect. Bullockia. As a result,
Bursera is paraphyletic but not Commiphora. We also find
that B. leptophloeos is embedded within Commiphora and
is basal to the clade containing sects. Abyssinicae,
Africanae, Campestres, and Opobalsameae, thus
corroborating the recent taxonomic placement of this species. The
presence of Commiphora within the New World, the equivalent
distributions of burseraceous genera between the Old and New World
tropics, and fossil remains of the family from more northerly
latitudes suggests a vicariant biogeographical history for this family
that can be explained, in part, by the boreotropics hypothesis.
Key words: boreotropics hypothesis, Burseraceae, Commiphora, ETS