Systematics Section / ASPT
Willyard, Ann , Liston, Aaron , Cronn, RC .
Integrating phylogenetic and population genetic approaches: A case study using Pinus washoensis.
Species-level evolutionary relationships can be difficult to unravel, especially when morphological character states are plastic as well as homoplasious, and molecular genealogies are clouded by incomplete lineage sorting and introgression. These factors have all been documented in Pinus (Pinaceae). We used three closely related pine species to explore the potential for an integrative phylogenetic and population genetic approach to resolve the evolutionary history of an enigmatic taxon. The high-elevation trees recognized as Pinus washoensis are distinct in some published analyses, yet contained within P. ponderosa sensu lato in others, and may introgress with sympatric P. jeffreyi. Further, high-elevation ponderosa pines in Oregon share some morphological features with recognized Washoe pine populations in Nevada and California. We took advantage of rather well developed molecular tools in pines to sample genomic regions thought to be evolving at rates appropriate for both species- and population-level comparisons. Two independent low-copy nuclear loci were sequenced for exemplars of P. jeffreyi, P. ponderosa, and P. washoensis (three to five individuals each). Phylogenetic hypotheses for each locus were tested in a Bayesian framework, and paternally inherited chloroplast haplotypes were used to infer patterns of recent pollen-mediated introgression.
For the population-level view, eight nuclear microsatellite loci developed for a congener were genotyped for ca. 20 individuals in each of 11 populations for the same three species. A comparison was made between genetic distances based on allele frequencies and several individual-based admixture models to infer within- and between-population variability. Combined evidence from two independent nuclear phylogenies, chloroplast haplotypes, and multi-locus population-level inferences allow us to test how robustly individuals cluster within populations and how well they fit with several putative species concepts. We provide evidence for a limited level of recent introgression, and evaluate the strength of the evidence that a footprint of ancient reticulation is still discernible.
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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
Low-copy Nuclear Markers.
Presentation Type: Oral Paper:Papers for Sections
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 1:00 PM