Biology subjects

Wehenkel, C.

Publications and source records attributed to Wehenkel, C..

5 recordsLinked to original sources

bioRxiv2026

Male-biased triploidy in Populus tremuloides and genomic structure of its southern relict populations

PremiseIsolated populations at the southern range edge of aspen (Populus tremuloides Michx.) offer a unique opportunity to study ploidy, clonality and distribution of sex under arid, high-elevation conditions. We aimed to characterize such traits, including potential sex biases and associations with ploidy, investigating previously unexamined Texan populations in a range-wide genomic framework of genetic structure and demographic history of this keystone species. MethodsWe combined new genotypic data from western Texas (Davis Mountains, Big Bend, Guadalupe Mountains) with preexisting datasets, assessing range-wide genetic diversity, clonality, ploidy, and sex. We further conducted ADMIXTURE and phylogenetic analyses, reconstructed historical effective population sizes (Ne) with Stairway Plot 2. ResultsTexan stands revealed high clonality, with diploid and triploid genets. Most Davis and Guadalupe Mountain individuals clustered with a southwestern U.S. lineage of aspen, whereas Big Bend individuals grouped with a Mexican, demonstrating for the first time the continuous northward geographic distributions of allele frequencies in aspen coherent with phylogenetics. The significant male bias in sex ratios, particularly among triploids, suggests dimorphism in survival or reproduction. No effect of elevation on sex was identified. Demographic inference indicated an ancient bottleneck ([~]1-2 Mya) common to all six lineages, but more recent historical Ne trajectories differ between the northern and southern regions. ConclusionsThese findings shed light on how clonality, ploidy, and sex have interacted in shaping dioecious plant species, highlighting the importance of incorporating such information into projections of how climate change and habitat loss will affect their distribution, abundance, and the extinction risk of their marginal populations.

evolutionary biology↗

bioRxiv2025

Elucidating continental-wide phylogeographic and adaptive processes shaping the genome-wide diversity of North America's most widely distributed tree

Past population dynamics during the Pleistocene ice age and the Holocene era have profoundly influenced the genetic structure and diversity of species. Environmental heterogeneity has further shaped local and regional adaptive variation. Here, we ask how historical processes have led to the current genetic diversity of a key North American species across its vast natural range and what genomic signatures indicate regional adaptive divergence and local adaptation. We used sequencing data from 1,903 Populus tremuloides Michx. (quaking aspen) trees to assess historical population dynamics and identify genotype-environment associations within and among the species major genetic lineages. The two northern and western North American aspen lineages exhibited historical population expansion patterns, while the southernmost lineage experienced a historical bottleneck consistent with past glacial oscillations. We found that the earliest split between genetic lineages of P. tremuloides occurred in the southern part of its distribution range. We further identified larger blocks of adaptive SNPs within separate genomic sequence regions on chromosomes 2 and 8 that may exhibit suppressed genetic recombination, contributing to the maintenance of regional and local adaptation in the species. Our study provides key insights into the evolutionary processes affecting adaptive genetic variation and phylogeography at a broad continental and regional scale, with implications for predicting species responses to future climate change.

evolutionary biology↗

bioRxiv2025

Soil microbiomes reveal different strategies for nitrogen acquisition in aspen-dominated stands from Mexico and Canada

Plant species shape soil microbiome composition through species-specific interactions. However, it is less clear how these interactions vary across populations that diverged a long time ago. In this study, we explore the influence of host genetic composition and edaphic factors on the soil microbiome of Populus tremuloides, one of North Americas most widespread tree species. Using 16S, 18S rRNA gene, and ITS2 region metabarcoding on soils from natural stands and potting mix, rhizosphere, and root samples from a greenhouse common garden, we examined prokaryotic and fungal communities in two aspen genetic groups. The Eastern Canada group represents boreal and cold temperate ecoregions, and the one from Northwestern Mexico represents warm temperate ecoregion. Variation in microbial community structure correlated with soil properties but results from common gardens indicated that the host genetic makeup may also play a role. The three ecoregions showed functional divergence: warm temperate sites hosted a higher abundance and diversity of nitrogen-fixing bacteria, while boreal stands exhibited stronger associations with ectomycorrhizal fungi. Our findings highlight how local adaptations to climate and soil conditions in aspen extend to their microbial partners, emphasizing the potential role of host-microbe interactions in shaping tree resilience and susceptibility to future climate changes.

evolutionary biology↗

bioRxiv2021

Macrosystem community assembly patterns are predicted by foundation tree species genetic connectivity and environment across the American Southwest

Macrosystems ecology is an emerging science that aims to integrate traditionally distinct disciplines to predict how hierarchical interacting processes influence the emergence of complex patterns across local to regional and global scales. Despite increased focus on cross-scale relationships and cross-disciplinary integration, few macroecology studies incorporate genetic-based processes. Here we used a community genetics approach to investigate the pattern-process relationships underlying the emergence of macroscale biodiversity patterns. We tested the hypothesis that environmental variation, geography, and genetic connectivity in a foundation tree species differentially predict associated community assembly patterns from local to continental scales. Using genome-wide SNP data, we assessed genetic connectivity as a function of genetic similarity and structure in Fremont cottonwood (Populus fremontii) across its distribution throughout the southwestern US and Mexico. For the same trees, we measured community composition, diversity, and abundance of leaf modifying arthropods and sequenced targeted amplicons of twig fungal endophytes. Five key findings emerged. (1) We identified three primary and six secondary population genetic groups within P. fremontii, which occupy distinct climate niches. (2) Both the leaf modifying arthropod and fungal endophyte communities were significantly differentiated across host tree ecotypes, with genetic distance among sampling locations explaining 13-17% of respective macroscale community structure. (3) For arthropods, environmental distance was the strongest driver of community similarity. (4) Conversely, host genetic connectivity was the most important contributor to macroscale endophyte community structure, with no significant contribution of environmental distance. (5) Furthermore, we observed a shift in the strength of interspecific relationships, with host genetics most strongly influencing associated communities at the intermediate population scale. Our findings suggest that genetic connectivity and environmental variation play integrated roles in macroscale community assembly, and their relative importance changes with scale. Thus, conservation genetic management of the diversity harbored within foundation species is vital for sustaining associated regional biodiversity.

ecology↗

bioRxiv2017

The role of hybridization during ecological divergence of southwestern white pine (Pinus strobiformis) and limber pine (P. flexilis)

Interactions between extrinsic factors, such as disruptive selection, and intrinsic factors, such as genetic incompatibilities among loci, can contribute to the maintenance of species boundaries. The relative roles of these factors in the establishment of reproductive isolation can be examined using species pairs characterized by gene flow throughout their divergence history. We investigated the process of speciation and the maintenance of species boundaries between Pinus strobiformis and P.flexilis. Utilizing ecological niche modeling, demographic modeling, and genomic cline analyses, we illustrated a history of divergence with continuous gene flow between these species. We found an abundance of advanced generation hybrids and a lack of loci exhibiting large allele frequency differences across the hybrid zone. Additionally, we found evidence for climate-associated variation in the hybrid index and niche divergence between parental species and the hybrid zone. Our results are consistent with extrinsic factors, such as climate, being an important isolating mechanism for these species. A buildup of intrinsic incompatibilities and of co-adapted gene complexes is also apparent in our results, although these appear to be in the earliest stages of development. This supports previous work in coniferous species demonstrating the importance of extrinsic factors in creating and enforcing species boundaries. Overall, we lend support to the hypothesis that varying strengths and directions of selection pressures across the long lifespans of conifers, in combination with their life history strategies, delay the evolution of strong intrinsic incompatibilities.

evolutionary biology↗