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Reticulate evolution, introgression, and intertribal gene capture in an allohexaploid grass
1University of Illinois at Chicago, Department of Biological Sciences, MC 066, 845 W. Taylor Street, Chicago, Illinois 60607, USA. robie@uic.edu
Systematic Biology
|February 18, 2004
Summary
Elymus repens exhibits complex reticulate evolution, with DNA data revealing at least five gene lineages. This pattern arises from allohexaploidy and introgression from within and beyond the Triticeae tribe.
Area of Science:
- Plant evolutionary biology
- Molecular phylogenetics
- Genomics
Background:
- Reticulate evolution in polyploid plants is complex.
- Elymus repens (creeping wheatgrass) is an allohexaploid in the Triticeae tribe.
- Previous studies suggested Hordeum and Pseudoroegneria as genome donors.
Purpose of the Study:
- To clarify the complex reticulate evolutionary patterns in Elymus repens.
- To identify the genome donors and assess introgression events using molecular data.
Main Methods:
- Phylogenetic analysis of chloroplast DNA (rpoA gene, trnT-trnF region).
- Analysis of nuclear starch synthase (SS) gene sequences.
- Comparison with cytogenetic data and existing molecular studies.
Main Results:
- Chloroplast DNA data identified three potential maternal donors: Pseudoroegneria, Thinopyrum, and Dasypyrum, with Pseudoroegneria being most likely.
- Nuclear SS gene data confirmed contributions from Hordeum and Pseudoroegneria.
- Unexpected nuclear contributions were found from Taeniatherum and two unidentified sources, one within Triticeae and one divergent outside the Triticeae clade.
Conclusions:
- Elymus repens displays an extreme reticulate pattern involving at least five distinct gene lineages.
- The species' genome is shaped by allohexaploidy and extensive introgression.
- Introgression involves donors both within and surprisingly divergent from the Triticeae tribe.