GRAHAM, SEAN W.1*, DONNA CHERNIAWSKY2, VINCENT L. BIRON1, and HARDEEP S. RAI1. 1Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9; 2The Provincial Museum of Alberta, Edmonton, Alberta, Canada, T5N 0M6. - Commelinoid monocot phylogeny revisited, using a large chloroplast data set.
The commelinoid monocots (sensu APG 1998) comprise four large orders
(Arecales, Commelinales, Poales and Zingiberales) and several taxa of
uncertain affinity. They include some of the largest flowering-plant
families and encompass an incredible array of ecological and
morphological diversity. Recent taxonomic treatments and molecular
studies have greatly clarified the circumscription of the commelinoids
and constituent orders, but many aspects of relationship in the group
remain poorly resolved at the family level and above. We present
results from an ongoing study of higher-order relationships in the
commelinoids, based on analysis of ~13.5 kb (unaligned) of DNA
sequence data per taxon, for 13 taxa in ten families. The regions
sampled include atpB, rbcL, ndhF, ten photosystem II genes, two ndh
genes, three ribosomal protein genes, three introns and two intergenic
spacer regions. Parsimony-based bootstrap analyses (using the Fitch
parsimony criterion) robustly support commelinoid monocot monophyly,
although several major taxa have not yet been sampled, including
Arecales. The position of the family Dasypogonaceae was not fully
resolved, but it is clearly isolated from Commelinales, Zingiberales
and Poales. Zingiberales is strongly supported as the sister-group of
the Commelinales. Our results support the inclusion of Hanguanaceae in
Commelinales, as was recently proposed by Chase et al. 2000,
although the monophyly of the redefined Commelinales (Commelinaceae,
Hanguanaceae, Haemodoraceae, Philydraceae and Pontederiaceae) was only
weakly supported. Within the Commelinales, Haemodoraceae and
Pontederiaceae were strongly supported as sister taxa, as were
Commelinaceae and Hanguanaceae. Philydraceae was moderately well
supported as the sister-group of Haemodoraceae-Pontederiaceae. We also
address the identity of the sister-group of the commelinoids, and
discuss various aspects of the molecular evolution of the regions
examined.
Key words: chloroplast phylogeny, Commelinales, Commelinoids, Hanguana, large-scale data