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Abstract Detail



Molecular Ecology and Evolution

Laport, Robert [1], Minckley, Robert [2], Ramsey, Justin [2].

Polyploid speciation in the North American creosote bush (Larrea tridentata, Zygophyllaceae): an integrative analysis of reproductive isolation and genetic divergence.

Genome duplication (polyploidy) is a common form of chromosome evolution in plants that often results in strong reproductive isolation. However, the relative significance of intrinsic reproductive barriers vs. post-duplication adaptation in polyploid lineage diversification is widely disputed because polyploids are often geographically, morphologically, and physiologically divergent from diploids. One widely cited example of polyploid speciation is the creosote bush (Larrea tridentata, Zygophyllaceae), a dominant species of the North American desert flora comprising three geographically isolated chromosome races (diploids in the Chihuahuan Desert, tetraploids in the Sonoran Desert, and hexaploids in the Mojave Desert). Yet, it remains unclear if the chromosome races of L. tridentata represent distinct taxonomic units, not only because of uncertainty over the strength of reproductive isolation, but also due to uncertainty over the degree to which they have diverged ecologically, morphologically/physiologically, and genetically. Here, we use a combination of field studies and DNA molecular analyses to test the hypothesis that the cytotypes of L. tridentata represent evolutionarily distinct lineages. We find that while intercytotype reproductive isolation is generally strong and mediated by floristically and ecologically distinct distributions, the magnitude of morphological, phenological, and genetic divergence varies for diploid-tetraploid and tetraploid-hexaploid sympatric interactions. Taken together, these results suggest that the cytotypes represent evolutionarily independent lineages and that ecological isolation plays a significant role driving divergence among the cytotypes.

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1 - University of Rochester, Department of Biology, River Campus, 476 Hutchison Hall, Rochester, NY, 14627, USA
2 - University of Rochester, Department of Biology, 213 Hutchison Hall, Rochester, NY, 14627, USA

Keywords:
speciation
cytogeography
flow cytometry
morphological divergence
hybrid inviability
gene flow.

Presentation Type: Oral Paper:Papers for Topics
Session: 46
Location: Newberry/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 2:00 PM
Number: 46003
Abstract ID:285
Candidate for Awards:None


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