1 April 2009 Genetic Distance between Species Predicts Novel Trait Expression in their Hybrids
Rike Stelkens, Ole Seehausen
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Interspecific hybridization can generate transgressive hybrid phenotypes with extreme trait values exceeding the combined range of the parental species. Such variation can enlarge the working surface for natural selection, and may facilitate the evolution of novel adaptations where ecological opportunity exists. The number of quantitative trait loci fixed for different alleles in different species should increase with time since speciation. If transgression is caused by complementary gene action or epistasis, hybrids between more distant species should be more likely to display transgressive phenotypes. To test this prediction we collected data on transgression frequency from the literature, estimated genetic distances between the hybridizing species from gene sequences, and calculated the relationship between the two using phylogenetically controlled methods. We also tested if parental phenotypic divergence affected the occurrence of transgression. We found a highly significant positive correlation between transgression frequency and genetic distance in eudicot plants explaining 43% of the variance in transgression frequency. In total, 36% of the measured traits were transgressive. The predicted effect of time since speciation on transgressive segregation was unconfounded by the potentially conflicting effects of phenotypic differentiation between species. Our analysis demonstrates that the potential impact hybridization may have on phenotypic evolution is predictable from the genetic distance between species.

© 2009 The Society for the Study of Evolution.
Rike Stelkens and Ole Seehausen "Genetic Distance between Species Predicts Novel Trait Expression in their Hybrids," Evolution 63(4), 884-897, (1 April 2009). https://doi.org/10.1111/j.1558-5646.2008.00599.x
Received: 9 July 2008; Accepted: 1 November 2008; Published: 1 April 2009

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adaptive evolution
comparative method
genetic distance
transgressive segregation
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