Systematics Section / ASPT
Tate, Jennifer A. , Beck, John , Small, Randall .
Phylogeny, taxonomy and character evolution in tribe Malveae (Malvaceae, subfamily Malvoideae).
Rigorous phylogenetic hypotheses provide a means to test not only taxonomic circumscriptions, but also specific evolutionary hypotheses. However, generic- and species-level studies can be complicated by a lack of such a framework at higher taxonomic levels. Of particular concern for these studies is the choice of outgroup, which can have a significant effect on the determination of monophyly, as well as the direction of character evolution. For our ongoing studies in tribe Malveae, the largest tribe in subfamily Malvoideae (Malvaceae), we are using nuclear and chloroplast sequence data to construct a rigorous framework for this diverse group. Comparison of a cpDNA-based phylogeny, using sequences from the rpl16 and matK-3'trnK introns, to a previous ITS phylogeny reveals overall similarities in the topologies, but with significant differences at basal nodes. In the chloroplast tree, Rhynchosida (which lacks an epicalyx) is sister to all other Malveae, which form two clades corresponding generally to the presence or absence of an epicalyx. In the ITS tree, Rhynchosida is embedded within the clade of taxa that lack an epicalyx. Phylogenetic hypotheses based on nuclear GBSSI (waxy) sequences also place Rhynchosida as sister to the rest of Malveae, but some generic placements within the two main subclades differ from both the cpDNA and ITS trees. Large and historically heterogeneous genera, such as Abutilon and Sida, prove to be as complicated as expected and illustrate the importance of taxon sampling in determining appropriate outgroups. Many of the morphological characters that have been emphasized historically for delimiting groups within the tribe appear to be more plastic than previously documented. Polyploidy has been a significant evolutionary process in many Malveae genera and may have been a particularly important factor in clades that are species rich and biogeographically diverse.
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1 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
2 - University of Tennessee, Department of Ecology and Evolutionary Biology, 437 Hesler Biology Building, 1406 Circle Drive, Knoxville, Tennessee, 37996-1100, USA
Presentation Type: Oral Paper
Date: Tuesday, August 16th, 2005
Time: 3:45 PM