Systematics Section / ASPT
Whitlock, Barbara A. , Hale, Amanda M. , Groff, Paul A. .
Biogeography and the evolution of life histories in Gentianopsis (Gentianaceae).
The species of Gentianopsis (including the fringed gentians) are widely distributed in the northern hemisphere and vary in whole-plant morphology and life history. Previous studies, sampling few North American taxa, found the monotypic Asian genus Pterygocalyx nested within Gentianopsis and claimed an Asian origin for the clade containing both genera. Our phylogenetic analysis of plastid trnLF and nuclear ITS sequence data from 17 taxa of Gentianopsis, plus Pterygocalyx, with multiple individuals sampled for most taxa and increased representation of North American lineages, does not support Pterygocalyx nested within Gentianopsis. The geographical origin of the clade including both genera cannot be specified at present due to lack of resolution among potential outgroups. We find complex biogeographic patterns within the genus and within some species. There are at least two lineages of Gentianopsis in North America: the clonal perennial G. barbellata and G. simplex in western mountain ranges, and a large, widely distributed radiation of short-lived monocarpic taxa. The second lineage does appear to have originated in Asia and subsequently colonized North America, and its recognition as an evolutionary entity is a novel finding of our analysis. The hypothesis that effective generation time is negatively correlated with substitution rates has been applied to short-lived vs. perennial plants. We will discuss assumptions of this approach and other subtleties in testing the hypothesis. Multiple amplicons of ITS were recovered for nearly all specimens examined. In all but one case, ITS copies from each species form a monophyletic group, suggesting that concerted evolution is acting at a sufficient rate to resolve relationships among species. However, in well-sampled species, the multiple ITS sequences from a single individual rarely form a monophyletic group. The use of ITS sequences for phylogeographic or other population-level studies is thus problematical.
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1 - University of Miami, Department of Biology, Coral Gables, FL, 33124, USA
Life history evolution
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 3:15 PM