Detecting genomic signatures of ecological speciation and parallel evolution in oaks
Final Report Abstract
Even though Darwin’s central idea that natural selection drives speciation is widely accepted, the mechanisms by which it may lead to reproductive isolation and the origin and maintenance of species integrity in the face of ongoing gene flow are still largely unknown. This project addresses this central question in evolutionary biology to provide additional evidence that divergent selection towards different optima can maintain species integrity in the face of gene flow and could have resulted in the evolution of new species (ecological speciation). Sympatric, multispecies oak (Fagaceae: Quercus) communities are model systems to study processes of ecological speciation with gene flow at the genome level. Thus, hybridization is common among oaks, and species boundaries in European white oaks (Quercus section Quercus) and in the North American red oaks (Quercus section Lobatae) are notoriously weak. However, recurrent gene flow among these species has not led to a loss of genetic cohesiveness or adaptive distinctness, and there is evidence that ecologically-driven selection plays an important role in limiting effective interspecific gene flow. This project focused on two hybridizing close relatives of the white oak group (section Quercus), Quercus robur and Quercus petraea, and of the red oak group (section Lobatae), Q. ellipsoidalis and Q. rubra, that have distinct and varied adaptations to drought. Whole genome resequencing revealed specific candidate genes for adaptive divergence in each oak section, but also common genes suggesting repeated adaptive evolution in phylogenetically diverged oak sections. Our findings hold significant relevance for the broader public, as they contribute to a deeper understanding of how trees evolve and adapt to changing environmental conditions. By exploring the genetic mechanisms behind adaptation in oaks, we provide valuable insights on candidate genes that can ultimately serve as a starting point for functional validation of genes associated with reproductive isolation and adaptive divergence in experimental settings.
Publications
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Oak Population Genomics. Population Genomics. Springer International Publishing.
Gailing, Oliver; Hipp, Andrew L.; Plomion, Christophe & Carlson, John E.
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Progress and Prospects of Population Genomics of North American Hardwoods. Population Genomics. Springer International Publishing.
Gailing, Oliver; Staton, Margaret; Schlarbaum, Scott E.; Coggeshall, Mark V.; Romero-Severson, Jeanne; Liang, Haiying & Carlson, John E.
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Use of Genomic Resources to Assess Adaptive Divergence and Introgression in Oaks. Forests, 12(6), 690.
Lazic, Desanka; Hipp, Andrew L.; Carlson, John E. & Gailing, Oliver
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A haplotype-resolved chromosome-scale genome for Quercus rubra L. provides insights into the genetics of adaptive traits for red oak species. G3: Genes, Genomes, Genetics, 13(11).
Kapoor, Beant; Jenkins, Jerry; Schmutz, Jeremy; Zhebentyayeva, Tatyana; Kuelheim, Carsten; Coggeshall, Mark; Heim, Chris; Lasky, Jesse R.; Leites, Laura; Islam-Faridi, Nurul; Romero-Severson, Jeanne; DeLeo, Victoria L.; Lucas, Sarah M.; Lazic, Desanka; Gailing, Oliver; Carlson, John & Staton, Margaret
