Original Article

Heredity (2013) 111, 474–485; doi:10.1038/hdy.2013.69; published online 17 July 2013

Admixture mapping of quantitative traits in Populus hybrid zones: power and limitations

D Lindtke1, S C González-Martínez2, D Macaya-Sanz2,3 and C Lexer1,4

  1. 1Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland
  2. 2INIA, Forest Research Centre, Department of Forest Ecology and Genetics, Madrid, Spain
  3. 3Technical University of Madrid, ETS Forestry Engineering, Department of Silviculture, Madrid, Spain
  4. 4Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK

Correspondence: Dr D Lindtke, Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Chemin du Musée 10, Fribourg 1700, Switzerland. E-mail: doro.lindtke@gmail.com

Received 13 January 2013; Revised 6 June 2013; Accepted 12 June 2013
Advance online publication 17 July 2013

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Abstract

Uncovering the genetic architecture of species differences is of central importance for understanding the origin and maintenance of biological diversity. Admixture mapping can be used to identify the number and effect sizes of genes that contribute to the divergence of ecologically important traits, even in taxa that are not amenable to laboratory crosses because of their long generation time or other limitations. Here, we apply admixture mapping to naturally occurring hybrids between two ecologically divergent Populus species. We map quantitative trait loci for eight leaf morphological traits using 77 mapped microsatellite markers from all 19 chromosomes of Populus. We apply multivariate linear regression analysis allowing the modeling of additive and non-additive gene action and identify several candidate genomic regions associated with leaf morphology using an information-theoretic approach. We perform simulation studies to assess the power and limitations of admixture mapping of quantitative traits in natural hybrid populations for a variety of genetic architectures and modes of gene action. Our results indicate that (1) admixture mapping has considerable power to identify the genetic architecture of species differences if sample sizes and marker densities are sufficiently high, (2) modeling of non-additive gene action can help to elucidate the discrepancy between genotype and phenotype sometimes seen in interspecific hybrids, and (3) the genetic architecture of leaf morphological traits in the studied Populus species involves complementary and overdominant gene action, providing the basis for rapid adaptation of these ecologically important forest trees.

Keywords:

model selection; dominance; overdominance; Populus alba; Populus tremula; leaf morphology