Abiotic factors predict taxonomic composition and genetic admixture in populations of hybridizing white oak species (Quercus sect. Quercus) on regional scale

Abstract

Knowing which drivers affect the spatial distribution of hybridizing species and their admixed individuals on local or regional scale can leverage our understanding about processes that shape taxonomic diversity. Hybridizing white oak species (Quercus sect. Quercus) represent an ideal study system to elucidate which environmental factors determine their relative abundance and admixture levels within admixed forest stands. To elaborate these relationships, we used 58 species-diagnostic single-nucleotide polymorphism (SNP) markers and high-resolution topographic and soil data to identify the environmental factors associated with taxonomic composition of individuals and populations in 15 mixed stands of Q. petraea and Q. pubescens in the Valais, an inner-Alpine valley in Switzerland. At the individual tree level, generalized linear models (GLMs) explained a relatively small part of variation (R2 = 0.32). At the population level, GLMs often explained a large part of variation (R2 = 0.54–0.69) of the taxonomic indices. Mean taxonomic composition of the sites depended mainly on altitude and geographic position. Moreover, the more within-site variation we found in predictors related to topographic position, the higher was the average genetic admixture of single trees. Our results show that a multitude of topographic and edaphic factors affect the taxonomic composition and admixture levels of these two hybridizing oak species on local scale and that regional heterogeneity of these factors promote taxonomic diversity and admixture. Overall, our study highlights the prospects of using tailored genetic resources and high-resolution environmental data to understand and predict taxonomic composition in response to changing environments.

Whole-genome screening for near-diagnostic genetic markers for four western European white oak species identification

“…In contrast to Q. pyrenaica, no reproductive barriers were observed in Q. pubescens when crosses were made with Q. petraea as female parent, as interspecific crosses were as successful as intraspecific crosses (Lepais et al 2013). Reduced barriers between these two species were corroborated by frequent admixture detected in genetic surveys conducted in mixed stands of Q. pubescens and Q. petraea (Alberto et al 2010;Neophytou 2014;Reutimann et al 2023). As a result, near-diagnostic SNPs of Q. pubescens and Q. petraea were more frequently shared between the two species (Fig.…”

“…pyrenaica (Lopez de Heredia et al 2009), and Q. petraea-Q. pubescens (Bruschi et al 2000;Reutimann et al 2020Reutimann et al , 2023. This brief overview of species admixture and problems of taxonomic classification based on morphological characteristics highlights the pressing need for a time-and cost-efficient molecular tool for reliable species assignment within European white oaks for use in forest science and management.…”

Introgression as an Important Driver of Geographic Genetic Differentiation within European White Oaks

“…(Fagaceae)-are of great economic and ecological importance and are promising species adapting to climate change in European forests [1]. The species' distributions and their dependency on environmental factors have been studied on stand and regional scales [2][3][4]. Recently the different abundance of the species has been linked to differences in their genomic composition and genetic adaptation [2].…”

“…The species' distributions and their dependency on environmental factors have been studied on stand and regional scales [2][3][4]. Recently the different abundance of the species has been linked to differences in their genomic composition and genetic adaptation [2].…”