Systematics Section / ASPT
Syring, John V. , Cronn, RC , Liston, Aaron .
Seqeuences of three nuclear loci reveal a population bottleneck in Pinus monticola.
In Pinus (Pinaceae), incomplete lineage sorting has been shown to render many species polyphyletic in phylogenetic analyses that include intraspecific sampling. The historic effective population size (Ne), as reflected by nucleotide diversity within contemporary species, seems to be the driving factor in determining whether species of pine show allelic monophyly. This theory was explored in the genetically diverse Pinus monticola. Based on the sampling of 9-31 haploid genotypes from three low-copy nuclear loci (cesA1, agp6, and LEA-like), estimates of Ne for P. monticola fall in the top half of values obtained from a broader survey of pines. However, a strong dichotomy in genetic diversity is apparent for samples originating north and south of the interface between the Cascade and Siskiyou mountain ranges in northern California. Across all loci, the number of unique alleles sequenced from the southern population was ca. 1.6 times larger than the northern population. Further, nucleotide diversity in the southern population averaged 10.7 times greater than in the northern population. These results correspond to an Ne that is nearly seven times greater in the southern population. Phylogenetic analyses from individual loci show the alleles of the southern population to be consistently polyphyletic, while only moderate exceptions are noted to the allelic monophyly of the northern population. The pattern of genetic diversity uncovered in P. monticola is consistent with a recent genetic bottleneck, perhaps resulting from multiple cycles of glaciation, contraction of the species into southern refugia, and subsequent recolonization northward from a small fraction of the ancestral gene pool. Whatever the cause, the unexpected allelic monophyly of the northern population is the direct result of historical processes that reduced its effective population size. This study has broader implications for phylogenetics in relating allelic monophyly to ecological phenomena that drive population-level genetics.
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1 - Montana State University-Billings, Biological and Physical Sciences, 1500 University Drive, Billings, MT, 59101, USA
2 - USDA Forest Service, Forest Genetics, Pacific Nothwest Research Station, 3200 SW Jefferson Way, Corvallis, Oregon, 97331, USA
3 - Oregon State University, Department of Botany & Plant Pathology, 2082 Cordley Hall, Corvallis, Oregon, 97331-2902, USA
incomplete lineage sorting
western white pine
Presentation Type: Oral Paper:Papers for Sections
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 1:30 PM