Genetic analysis of post-mating reproductive barriers in hybridizing European Populus species

Macaya-Sanz, David; Suter, Leonie; Joseph, Jeffrey A.; Barbará, Thelma; Alba, N.; González-Martínez, S. C.; Widmer, Alex; Lexer, Christian

doi:10.1038/hdy.2011.35

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Genetic analysis of post-mating reproductive barriers in hybridizing European Populus species

Macaya-Sanz, David Department of Forest Ecology and Genetics, Center of Forest Research, CIFOR-INIA, Carretera de A Coruña, Madrid, Spain
Suter, Leonie Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK - ETH Zürich, Institute of Integrative Biologie, Switzerland
Joseph, Jeffrey A. Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK
Barbará, Thelma Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK - Department of Biology, University of Fribourg, Unit of Ecology and Evolution, Switzerland
Alba, N. Department of Forest Ecology and Genetics, Center of Forest Research, CIFOR-INIA, Carretera de A Coruña, Madrid, Spain
González-Martínez, S. C. Department of Forest Ecology and Genetics, Center of Forest Research, CIFOR-INIA, Carretera de A Coruña, Madrid, Spain
Widmer, Alex ETH Zürich, Institute of Integrative Biologie, Switzerland
Lexer, Christian Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK - Department of Biology, University of Fribourg, Unit of Ecology and Evolution, Switzerland

18.05.2011

Published in:

Heredity. - 2011, vol. 107, p. 478–486

English Molecular genetic analyses of experimental crosses provide important information on the strength and nature of post-mating barriers to gene exchange between divergent populations, which are topics of great interest to evolutionary geneticists and breeders. Although not a trivial task in long-lived organisms such as trees, experimental interspecific recombinants can sometimes be created through controlled crosses involving natural F₁'s. Here, we used this approach to understand the genetics of post-mating isolation and barriers to introgression in Populus alba and Populus tremula, two ecologically divergent, hybridizing forest trees. We studied 86 interspecific backcross (BC₁) progeny and >350 individuals from natural populations of these species for up to 98 nuclear genetic markers, including microsatellites, indels and single nucleotide polymorphisms, and inferred the origin of the cytoplasm of the cross with plastid DNA. Genetic analysis of the BC₁ revealed extensive segregation distortions on six chromosomes, and >90% of these (12 out of 13) favored P. tremula donor alleles in the heterospecific genomic background. Since selection was documented during early diploid stages of the progeny, this surprising result was attributed to epistasis, cyto-nuclear coadaptation, heterozygote advantage at nuclear loci experiencing introgression or a combination of these. Our results indicate that gene flow across ‘porous’ species barriers affects these poplars and aspens beyond neutral, Mendelian expectations and suggests the mechanisms responsible. Contrary to expectations, the Populus sex determination region is not protected from introgression. Understanding the population dynamics of the Populus sex determination region will require tests based on natural interspecific hybrid zones.

Faculty

Faculté des sciences et de médecine

Department

Département de Biologie

Language