Molecular Ecology and Evolution
Moody, Michael L. , Rieseberg, Loren H. .
Phylogeny, congruence testing and linkage disequilibrium: An approach to identify ancient hybridization using the annual sunflower clade (Helianthus).
Taxon-specific molecular markers and linkage disequilibrium are commonly employed to identify contemporaneous hybridization events, but the footprints of hybridization are rapidly lost over time due to mutation and recombination. To identify more ancient hybridization events scientists have relied on incongruence between phylogenetic trees based on different genes or genomes. This approach is not entirely satisfactory, because other evolutionary processes may lead to phylogenetic incongruence (e.g., lineage sorting, gene duplication, evolutionary rate heterogeneity). Linder and Rieseberg (2004) recently hypothesized a method utilizing the concept that after a hybridization event and during recombination closely linked genes will remain physically associated on a chromosome. Subsequently, if a lineage has a hybrid ancestry, phylogenetic trees from tightly linked genes are not only likely to be congruent, but they also should place the hybrid lineage with the parent from which the chromosomal segment was originally inherited. In addition, trees from this chromosomal segment should be incongruent with trees derived from genes/chromosomal segments inherited from the opposing parent. This approach was tested on three well corroborated hybrid annual sunflower (Helianthus) species using EST sequences to demonstrate “proof of principle” and then applied to another Helianthus taxon, suspected to be an ancient hybrid lineage (H. bolanderi/H. exilis). Results were not consistent overall and were highly dependent on taxon sampling among the annual sunflower clade. Suspected confounding factors include recurrent gene exchange between hybrid parental taxa, gene duplication events and divergence in rates of molecular evolution.
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1 - University of Western Australia, Plant Biology, 35 Stirling Highway, Crawley, WA, 6009, Australia
2 - Univeristy of British Columbia, Botany, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, July 29th, 2008
Time: 1:45 PM