Multiple evolutionary processes drive the patterns of genetic differentiation in a forest tree species complex
Article first published online: 26 FEB 2013
© 2012 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd.
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Ecology and Evolution
Volume 3, Issue 1, pages 1–17, January 2013
How to Cite
Ecology and Evolution 2013; 3(1): 1–17
- Issue published online: 26 FEB 2013
- Article first published online: 26 FEB 2013
- Manuscript Accepted: 3 OCT 2012
- Manuscript Revised: 26 SEP 2012
- Manuscript Received: 8 AUG 2012
- Australian Research Council Linkage. Grant Number: LP0455522
- Discovery Grant. Grant Number: DP0986491
- CRC for Forestry and the Central Science Laboratory
- Blue gum;
- clinal variation;
- conservation genetics;
- gene pool management;
- genetic diversity;
- microsatellite DNA;
Forest trees frequently form species complexes, complicating taxonomic classification and gene pool management. This is certainly the case in Eucalyptus, and well exemplified by the Eucalyptus globulus complex. This ecologically and economically significant complex comprises four taxa (sspp. bicostata, globulus, maidenii, pseudoglobulus) that are geographically and morphologically distinct, but linked by extensive “intergrade” populations. To resolve their genetic affinities, nine microsatellites were used to genotype 1200 trees from throughout the natural range of the complex in Australia, representing 33 morphological core and intergrade populations. There was significant spatial genetic structure (FST = 0.10), but variation was continuous. High genetic diversity in southern ssp. maidenii indicates that this region is the center of origin. Genetic diversity decreases and population differentiation increases with distance from this area, suggesting that drift is a major evolutionary process. Many of the intergrade populations, along with other populations morphologically classified as ssp. pseudoglobulus or ssp. globulus, belong to a “cryptic genetic entity” that is genetically and geographically intermediate between core ssp. bicostata, ssp. maidenii, and ssp. globulus. Geography, rather than morphology, therefore, is the best predictor of overall genetic affinities within the complex and should be used to classify germplasm into management units for conservation and breeding purposes.