Willyard, Ann M. , Wallace, Lisa Ellen , Wagner, Warren L. , Weller, Stephen G. , Sakai, Ann K. , Nepokroeff, Molly .
Estimating the species tree for Hawaiian Schiedea (Caryophyllaceae) from multiple loci in the presence of reticulate evolution.
Schiedea (Caryophyllaceae) is a monophyletic genus containing 32 extant species that arose from a single colonization of the Hawaiian Islands. Schiedea is one of the best examples of adaptive radiation in Hawaii, with species inhabiting a range of habitats and exhibiting a variety of growth forms. Dramatic transitions in breeding systems (from hermaphroditism to dimorphism or autogamy) correlate with habitat, and are likely driven by availability of pollinators. A well-resolved species tree of this recent radiation would allow fuller exploration of the forces that influence shifts in breeding systems, patterns and timing of island colonization, and relationships among species in the lineage. Our study included the most thorough sampling to date for this lineage: 91 accessions (2 to 5 per species) and 4 independent genetic partitions: 8 chloroplast and 3 low-copy nuclear loci (9217 bps). We explore various methods to synthesize congruent signal among gene trees to build a species tree, ways to distinguish analytical artifacts from incomplete lineage sorting and various tests of hard polytomies that signify simultaneous speciation. We also use multiple lines of inference to examine the lability of breeding systems within this intriguing lineage. Our results support tests of species monophyly, but also strong incongruence that may reveal introgression. Within Schiedea, chloroplast lineages have diverged dramatically from nuclear genealogies in several cases. An inter-island migrant taking up the chloroplast lineage of a resident congener best explains two instances of cytonuclear discordance. Despite reticulate evolution from early hybridization events and limited recent introgression, every species has a significant genealogical sorting index, indicating that currently recognized species correspond to monophyletic groups.
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1 - University of South Dakota, Department of Biology, 414 E. Clark St., Vermillion, SD, 57069, USA
2 - Mississippi State University, Department of Biological Sciences, P. O. Box GY, Mississippi State, Mississippi, 39762
3 - National Museum of Natural History, Smithsonian Institution, Botany, P.O. Box 37012, MRC 166, Washington, DC, 20013-7012, USA
4 - University of California Irvine, Department of Ecology & Evolutionary Biology, 321 Steinhaus Hall, Irvine, California, 92697-2525, USA
5 - University of South Dakota, Department of Biology, 414 East Clark Street, Vermillion, South Dakota, 57069, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Magpie A/Cliff Lodge - Level B
Date: Tuesday, July 28th, 2009
Time: 10:30 AM