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ABSTRACT Hybridization and interspecific gene flow play a substantial role in the evolution of plant taxa. The eastern North American white oak syngameon, a group of approximately 15 ecologically, morphologically and genomically distinguishable species, has long been recognised as a model system for studying introgressive hybridization in temperate trees. However, the prevalence, genomic context and environmental correlates of introgression in this system remain largely unknown. To assess introgression in the eastern North American white oak syngameon and population structure within the widespreadQuercus macrocarpa, we conducted a rangewide survey ofQ. macrocarpaand four sympatric eastern North American white oak species. Using a Hyb‐Seq approach, we assembled a dataset of 3412 thinned single‐nucleotide polymorphisms (SNPs) in 445 enriched target loci including 62 genes putatively associated with various ecological functions, as well as associated intronic regions and some off‐target intergenic regions (not associated with the exons). Admixture analysis and hybrid class inference demonstrated species coherence despite hybridization and introgressive gene flow (due to backcrossing of F1s to one or both parents). Additionally, we recovered a genetic structure withinQ. macrocarpaassociated with latitude. Generalised linear mixed models (GLMMs) indicate that proximity to range edge predicts interspecific admixture, but rates of genetic differentiation do not appear to vary between putative functional gene classes. Our study suggests that gene flow between eastern North American white oak species may not be as rampant as previously assumed and that hybridization is most strongly predicted by proximity to a species' range margin.
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This content will become publicly available on January 27, 2026
Powdery Mildews on North American Oaks: High Levels of Diversity and Pathogen‐Host Coevolution
ABSTRACT Erysiphespecies infecting oaks in North America are common and widespread, but compared to Asia and Europe, the taxonomy and phylogeny of North American species is unknown. The present study addresses this dispairity. Comprehensive multilocus phylogenetic analyses, includingCAM,GAPDH,GS, ITS,RPB2andTUB, revealed a high degree of co‐evolution between North American oaks and theErysiphespp. that infect them. A concatenated multilocus tree and individual trees based on single loci revealed many highly supported species clades. The clades are formally named to conform with the current taxonomic classification. Available names, such asE. abbreviata,E. calocladophoraandE. extensa, are associated with corresponding clades, and are newly circumscribed supported by ex‐type sequences or, if not available, by the designation of epitypes with ex‐epitype sequences.Erysiphe densissimais reintroduced for a clade that corresponds to the old name ‘E. extensavar.curta’. Eight new species are described, includingErysiphe carolinensis,E. gambelii,E. occidentalis,E. phellos,E. pseudoextensa,E. quercophila,E. quercus‐laurifoliaeandE. schweinitziana. A new diagnostically and taxonomically relevant trait associated with the anamorphs of North AmericanErysiphespecies on oaks has been assssed. This is a special conidiophore‐like lateral outgrowth of the superficial hyphae, comparable to ‘aerial hyphae,’ which are also known for species of the powdery mildew genusCystothecawhich also infectQuercusspecies.
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- Award ID(s):
- 2402193
- PAR ID:
- 10568628
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Forest Pathology
- Volume:
- 55
- Issue:
- 1
- ISSN:
- 1437-4781
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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