Patterns and Mechanisms of Evolution of Island Plants
Nepokroeff, Molly , Wallace, Lisa , Wagner, Warren , Weller, Stephen G. , Sakai, Ann K. .
Phylogeography of Hawaiian Schiedea: a multigene, coalescent approach.
The endemic Hawaiian plant lineage Schiedea represents an excellent model system for examining evolutionary processes on islands as the genus comprises one of the five largest radiations of plant species from a single colonization, and is one of the most diverse in terms of growth form, breeding systems, and habitat preference. Studies of the ecology of breeding systems in Schiedea have become classic examples of the evolution of floral dimorphism on islands. However, phylogenetic relationships within Schiedea remain poorly resolved. Genealogical relationships are central to understanding evolutionary transitions in breeding systems from hermaphrodite to other forms, including dimorphism and autogamy. Phylogenetic analyses have corroborated the monophyly and origin of the clade. We investigated phylogenetic relationships among the 33 extant species of Schiedea using the single copy number nuclear Nia intron and several plastid markers, and several individuals/populations per species. The presence of several polyphyletic clones in both data sets suggests the retention of introgressed alleles resulting from historical hybridization. Indeed, interspecific gene flow may be characteristic of the Schiedea lineage, and may have played a role in the spread of male-sterility mutations involved in the evolution of floral dimorphism. To further characterize patterns of interspecific hybridization, we examined genealogies of S. salicaria and S. menziesii and their hybrid progeny using nuclear and chloroplast DNA sequences in a coalescent framework. Chloroplast markers suggest that and S. menziesii is the maternal parent of all sampled hybrids, an interesting finding given that S. salicaria is gynodioecious and S. menziesii is hermaphroditic. Additionally, several hybrids exhibited variation in Nia sequences not present in parental species, but which may support the presence of gene flow from unsampled individuals. These results suggest that interspecific hybridization patterns in Schiedea are complex and may warrant consideration in light of reconstructing the phylogenetic history of this group.
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1 - University of South Dakota, Department of Biology, 414 East Clark Street, Vermillion, South Dakota, 57069, USA
2 - Smithsonian Institution, Department of Botany MRC 166, National Museum Of Natural History, Po Box 37012, Washington, DC, 20560-0166, USA
3 - University of California, Irvine, Department of Ecology and Evolution, 321 Steinhaus Hall, UCI, Irvine, California, 92697, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Salon J - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 2:30 PM