Systematics Section / ASPT
Willyard, Ann , Liston, Aaron , Cronn, RC .
What can we learn from a multi-locus nuclear phylogeny of the “hard” pines ( Pinus subgenus Pinus, Pinaceae)?
THE lack of species-level resolution in previous phylogenies of Pinus subgenus Pinus has been attributed to limited taxonomic sampling, homoplasy (morphological characters), intra-individual variation (nrITS), and slow divergence rates (chloroplast). Pinus species are long-lived, predominantly outcrossing trees with numerous reports of limited local natural hybridization and introgression. These characteristics are expected to contribute to large effective population sizes and long coalescence times for nuclear loci. Paternal chloroplast inheritance, long-distance pollen dispersal, and weakly developed mating barriers in Pinus have the potential to result in chloroplast genomes that track a different evolutionary history than most nuclear loci. Sectional divergences within subgenus Pinus have now been estimated to be quite young, and some higher taxa (subsections) may have radiated within a short time frame as recently as 13 million years ago. A recent nuclear phylogeny of Pinus subgenus Strobus identified significant allelic nonmonophyly (attributed to incomplete lineage sorting) in about one-third of the species, and we have increasing evidence for this phenomenon in Pinus subgenus Pinus as well. This study investigates the power of multiple nuclear loci (primarily intron sequences), each diverging at a faster rate than chloroplast loci, to reveal information about evolutionary relationships of recently diverged species. Three unlinked low-copy nuclear loci are being sequenced for two individuals from each of the ca. 77 species in subgenus Pinus. Traditional phylogenetic approaches are being compared to coalescent-based methods that utilize the among-locus variation between the gene genealogies to infer historical relationships in this well-studied but phylogenetically recalcitrant genus.
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1 - Oregon State University, Department of Botany & Plant Pathology, 2082 Cordley Hall, Corvallis, Oregon, 97331-2902, USA
2 - USDA Forest Service, Forest Genetics, Pacific Nothwest Research Station, 3200 SW Jefferson Way, Corvallis, Oregon, 97331, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 144/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 9:00 AM