Genetic integration of species diagnostic characters and their evolutionary responses to selection within hybridizing oaks

Presentation given at the XX International Botanical Conference, Madrid, Spain, July 21–27, 2024.

Author:

Ilga M. Porth

Affiliation:

Department of Forest and Wood Sciences, Laval University, Quebec, Canada

Abstract:

The European oak species complex Quercus petraea/robur represents the best studied system for temperate tree speciation and population dynamics. Due to their extensive historical introgression, genetic clustering follows a continuous transition between the species, with only few species-specific clusters rather than strong species differentiation. Investigation of GxE and species’ integrity found that GxE decreases with increasing species integrity, and therefore GxE interactions across the studied species' discriminant leaf traits were strongly driven by the level of introgression between species across tested forest stands. Using a marker-based relationship matrix, we estimated coefficients of genetic integration for each trait, with those leaf traits being the least integrated that showed the highest species discriminatory power. Historical introgression seemed highest within cooler and wetter environments, while organismal modularity allowed for the independent evolution in oak species’ morphology relating to ecological adaptation. This was corroborated by networks of genetic correlations. Hence, low within-species genetic integration of traits allows for the highest difference in evolutionary response to selection between species. Thus, less integrated traits can effectively drive Quercus species divergence, and more specifically, the evolutionary response to selection for leaf veins’ function could explain the difference in water use efficiency and gas exchange between the different oak species. Our study highlights the importance of knowledge about the genetic, epistatic, and plastic effects associated with species diagnostic traits when considering conservation units in oak.