Management strategies, such as assisted gene flow, can increase resilience to climate change in tree populations. Knowledge of evolutionary history and genetic structure of species are needed to assess the risks and benefits of different strategies. , or Island Oak, is a rare oak restricted to six Channel Islands in California, United States, and Baja California, Mexico.
View Article and Find Full Text PDFWoody plants create the ecosystems they occupy and shape their biodiversity. Today's rapidly warming climate threatens these long-lived species by creating new environments in which existing populations become maladapted. Plants show enormous phenotypic diversity in response to environmental change, which can be caused by genotype or epigenetic mechanisms that influence the expression of the underlying DNA sequence.
View Article and Find Full Text PDFIsland oak (Quercus tomentella) is a rare relictual island tree species that exists only on six islands off the coast of California and Mexico, but was once widespread throughout mainland California. Currently, this species is endangered by threats such as non-native plants, grazing animals, and human removal. Efforts for conservation and restoration of island oak currently underway could benefit from information about its range-wide genetic structure and evolutionary history.
View Article and Find Full Text PDFJuglans californica, California walnut, is a vulnerable small tree that is locally abundant but restricted to woodland and chaparral habitats of Southern California threatened by urbanization and land use change. This species is the dominant species in a unique woodland ecosystem in California. It is one of 2 endemic California walnut species (family Juglandaceae).
View Article and Find Full Text PDFThe California Conservation Genomics Project (CCGP) is a unique, critically important step forward in the use of comprehensive landscape genetic data to modernize natural resource management at a regional scale. We describe the CCGP, including all aspects of project administration, data collection, current progress, and future challenges. The CCGP will generate, analyze, and curate a single high-quality reference genome and 100-150 resequenced genomes for each of 153 species projects (representing 235 individual species) that span the ecological and phylogenetic breadth of California's marine, freshwater, and terrestrial ecosystems.
View Article and Find Full Text PDFBackground And Aims: Contemporary patterns of genetic admixture reflect imprints of both ancient and recent gene flow, which can provide us with valuable information on hybridization history in response to palaeoclimate change. Here, we examine the relationships between present admixture patterns and past climatic niche suitability of two East Asian Cerris oaks (Quercus acutissima and Q. chenii) to test the hypothesis that the mid-Pliocene warm climate promoted while the Pleistocene cool climate limited hybridization among local closely related taxa.
View Article and Find Full Text PDFAncient introgression can be an important source of genetic variation that shapes the evolution and diversification of many taxa. Here, we estimate the timing, direction, and extent of gene flow between two distantly related oak species in the same section (Quercus sect. Quercus).
View Article and Find Full Text PDFUnderstanding how the environment shapes genetic variation provides critical insight about the evolution of local adaptation in natural populations. At multiple spatial scales and multiple geographic contexts within a single species, such information could address a number of fundamental questions about the scale of local adaptation and whether or not the same loci are involved at different spatial scales or geographic contexts. We used landscape genomic approaches from three local elevational transects and rangewide sampling to (a) identify genetic variation underlying local adaptation to environmental gradients in the California endemic oak, Quercus lobata; (b) examine whether putatively adaptive SNPs show signatures of selection at multiple spatial scales; and (c) map putatively adaptive variation to assess the scale and pattern of local adaptation.
View Article and Find Full Text PDFBackground: As higher education institutions strive to effectively support an increasingly diverse student body, they will be called upon to provide their faculty with tools to teach more inclusively, especially in science, technology, engineering, and mathematics (STEM) classrooms where recruitment and retention of students from underrepresented and disadvantaged groups present long-standing challenges. Pedagogical training approaches to creating inclusive classrooms involve interventions that raise awareness of student and instructor social identities and explore barriers to learning, such as implicit bias, microaggressions, stereotype threat, and fixed mindset. Such efforts should focus on embracing diversity as an asset leveraged to benefit all students in their learning.
View Article and Find Full Text PDFEpigenetic modifications such as DNA methylation, where methyl groups are added to cytosine base pairs, have the potential to impact phenotypic variation and gene expression, and could influence plant response to changing environments. One way to test this impact is through the application of chemical demethylation agents, such as 5-Azacytidine, which inhibit DNA methylation and lead to a partial reduction in DNA methylation across the genome. In this study, we treated 5-month-old seedlings of the tree, , with foliar application of 5-Azacytidine to test whether a reduction in genome-wide methylation would cause differential gene expression and change phenotypic development.
View Article and Find Full Text PDFClimate change over the next century is predicted to cause widespread maladaptation in natural systems. This prediction, as well as many sustainable management and conservation practices, assumes that species are adapted to their current climate. However, this assumption is rarely tested.
View Article and Find Full Text PDFDrought is a major stress for plants, creating a strong selection pressure for traits that enable plant growth and survival in dry environments. Many drought responses are conserved species-wide responses, while others vary among populations distributed across heterogeneous environments. We tested how six populations of the widely distributed California valley oak (Quercus lobata) sampled from contrasting climates would differ in their response to soil drying relative to well-watered controls in a common environment by measuring ecophysiological traits in 93 individuals and gene expression (RNA-seq) in 42 individuals.
View Article and Find Full Text PDFThe tree of life is highly reticulate, with the history of population divergence emerging from populations of gene phylogenies that reflect histories of introgression, lineage sorting and divergence. In this study, we investigate global patterns of oak diversity and test the hypothesis that there are regions of the oak genome that are broadly informative about phylogeny. We utilize fossil data and restriction-site associated DNA sequencing (RAD-seq) for 632 individuals representing nearly 250 Quercus species to infer a time-calibrated phylogeny of the world's oaks.
View Article and Find Full Text PDFPremise: In plant groups with limited intrinsic barriers to gene flow, it is thought that environmental conditions can modulate interspecific genetic exchange. Oaks are known for limited barriers to gene flow among closely related species. Here, we use Quercus as a living laboratory in which to pursue a fundamental question in plant evolution: Do environmental gradients restrict or promote genetic exchange between species?
Methods: We focused on two North American oaks, the rare Quercus dumosa and the widespread Q.
Local adaptation is a critical evolutionary process that allows plants to grow better in their local compared to non-native habitat and results in species-wide geographic patterns of adaptive genetic variation. For forest tree species with a long generation time, this spatial genetic heterogeneity can shape the ability of trees to respond to rapid climate change. Here, we identify genomic variation that may confer local environmental adaptations and then predict the extent of adaptive mismatch under future climate as a tool for forest restoration or management of the widely distributed high-elevation oak species in Mexico.
View Article and Find Full Text PDFBackground: Hybridization and introgression are common phenomena among oak species. These processes can be beneficial by introducing favorable genetic variants across species (adaptive introgression). Given that drought is an important stress, impacting physiological and morphological variation and limiting distributions, our goal was to identify drought-related genes that might exhibit patterns of introgression influenced by natural selection.
View Article and Find Full Text PDFA long-term debate in evolutionary biology is the extent to which reproductive isolation is a necessary element of speciation. Hybridizing plants in general are cited as evidence against this notion, and oaks specifically have been used as the classic example of species maintenance without reproductive isolation. Here, we use thousands of SNPs generated by RAD sequencing to describe the phylogeny of a set of sympatric white oak species in California and then test whether these species exhibit pervasive interspecific gene exchange.
View Article and Find Full Text PDFSeed and pollen dispersal shape patterns of gene flow and genetic diversity in plants. Pollen is generally thought to travel longer distances than seeds, but seeds determine the ultimate location of gametes. Resolving how interactions between these two dispersal processes shape microevolutionary processes is a long-standing research priority.
View Article and Find Full Text PDFIdentifying and quantifying the importance of environmental variables in structuring population genetic variation can help inform management decisions for conservation, restoration, or reforestation purposes, in both current and future environmental conditions. Landscape genomics offers a powerful approach for understanding the environmental factors that currently associate with genetic variation, and given those associations, where populations may be most vulnerable under future environmental change. Here, we applied genotyping by sequencing to generate over 11,000 single nucleotide polymorphisms from 311 trees and then used nonlinear, multivariate environmental association methods to examine spatial genetic structure and its association with environmental variation in an ecologically and economically important tree species endemic to Hawaii, .
View Article and Find Full Text PDFHere we study hybridization, introgression and lineage diversification in the widely distributed canyon live oak (Quercus chrysolepis) and the relict island oak (Q. tomentella), two Californian golden cup oaks with an intriguing biogeographical history. We employed restriction-site-associated DNA sequencing and integrated phylogenomic and population genomic analyses to study hybridization and reconstruct the evolutionary past of these taxa.
View Article and Find Full Text PDFQuantitative genetic theory provides a means of estimating the evolutionary potential of natural populations. However, this approach was previously only feasible in systems where the genetic relatedness between individuals could be inferred from pedigrees or experimental crosses. The genomic revolution opened up the possibility of obtaining the realized proportion of genome shared among individuals in natural populations of virtually any species, which could promise (more) accurate estimates of quantitative genetic parameters in virtually any species.
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