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Interspecific gene flow in sympatric oaks
1Department of Biology, Washington University, St. Louis, MO 63130, USA.
Summary
Gene flow occurs between white oak species in the eastern US, with chloroplast DNA showing exchange, but nuclear ribosomal DNA variants suggest limited nuclear gene flow, maintaining species distinctiveness.
Area of Science:
- Botany
- Genetics
- Evolutionary Biology
Background:
- White oak species (Quercus) in the eastern US exhibit distinct morphological and ecological traits.
- These interfertile species often coexist in mixed stands, with occasional natural hybridization.
Purpose of the Study:
- To investigate the extent of gene flow between five sympatric white oak species.
- To compare the patterns of genetic variation in chloroplast DNA (cpDNA) and nuclear ribosomal DNA (nrDNA).
Main Methods:
- Analysis of restriction site variation in cpDNA among five white oak species.
- Examination of length variants in nuclear ribosomal DNA (nrDNA) within these species.
Main Results:
- cpDNA restriction site markers indicated localized gene exchange and appreciable gene flow between sympatric white oak species.
- A specific length variant of the nrDNA was found to be species-specific across all studied white oaks.
Conclusions:
- Chloroplast DNA genotypes are exchanged more freely between white oak species than nuclear genes.
- The species-specific nrDNA variant, alongside morphological and ecological differences, suggests restricted nuclear gene flow, aiding in species differentiation.