Geology topics

Bryce A. Richardson

Publications and source records attributed to Bryce A. Richardson.

15 recordsLinked to original sources

USGS2025

Suturing fragmented landscapes: Mosaic hybrid zones in plants may facilitate ecosystem resiliency

Many widespread plant taxa of western North America have diversified into phenotypically and genetically divergent lineages due to complex biogeographic histories across heterogeneous landscapes. Mosaic hybrid zones can form when geographically co-occurring, yet environmentally distinct, lineages cross-pollinate and form hybrids that occupy unique environmental niches absent of a geographic cline. This expands the total environmental space across which parental and hybrid individuals grow, resulting in larger, less fragmented geographic distributions. Here, we highlight hybridization mosaics across three study systems containing taxa critical to widespread plant communities in western North America: Ericameria nauseosa , Artemisia tridentata , and Sphaeralcea fendleri . The systems contain diverged taxa that co-occur across the landscape and hybridize readily. Hybridization among taxa has facilitated niche expansion into intermediate environments consistent with unique combinations of adaptive genetic variation, creating more continuity within each study system—study systems occupy ~820 to 270,000 km 2 more geographic area by virtue of hybridization. Furthermore, hybrids are predicted to play important roles in future climates, as they may occupy 8 to 475% larger distributions compared to present. Convergent patterns signal mosaic hybridization as an underappreciated mechanism with broad ecological and evolutionary ramifications. Leveraging mosaic hybridization may assist the creation of restoration management plans that aim to mitigate the deleterious effects of habitat fragmentation on ecosystems in the context of climate change.

western United States↗

USGS2025

Cytotype and local adaptation drive phenotypic variation in two subspecies of big sagebrush (Artemisia tridentata)

Big sagebrush ( Artemisia tridentata ) is a widespread and locally dominant shrub throughout many ecosystems in western North America. A. tridentata ssps. tridentata and wyomingensis are two subspecies whose populations occupy the warm-arid regions of the species range and whose trailing edge is threatened by climate change. Previous studies have presented conflicting results in relation to the genetic control of physiological variation in A. tridentata . Understanding how different genetic factors contribute to physiological variation can provide insight into how these two subspecies may respond to future climate change. To explore possible variation among and within two subspecies of A. tridentata , we measured physiological and morphological traits in A . t . tridentata and A. t. wyomingensis during mid-summer (July), seven years after establishment in a common garden. Contributions to trait variation were quantified for both genetic (subspecies and cytotype) and environmental (climate-of-origin) factors. Measurements revealed an unequal contribution to phenotypic variation by subspecies, cytotype, and climate-of-origin. Ploidy and climate-of-origin were more important than subspecies in driving phenotypic variation in A. tridentata. These findings suggest that A. tridentata has a highly plastic drought response, or that culling (mortality over time due to environmental factors) in the common garden over seven years has led to a lack of genetic diversity within the garden. Understanding what factors drive phenotypic expression in big sagebrush can provide better insight into how climate change may affect migration and extirpation and may aid in the effectiveness of restoration efforts.

Idaho↗

USGS2022

Spatial models can improve the experimental design of field-based transplant gardens by preventing bias due to neighborhood crowding

Field-based transplant gardens, including common and reciprocal garden experiments, are a powerful tool for studying genetic variation and gene-by-environment interactions. These experiments assume that individuals within the garden represent independent replicates growing in a homogenous environment. Plant neighborhood interactions are pervasive across plant populations and could violate assumptions of transplant garden experiments. We demonstrate how spatially explicit models for plant–plant interactions can provide novel insights on genotypes' performance in field-transplant garden designs. We used individual-based models, based on data from a sagebrush ( Artemisia spp.) common garden, to simulate the impact of spatial plant–plant interactions on between-group differences in plant growth. We found that planting densities within the range of those used in many common gardens can bias experimental outcomes. Our results demonstrate that higher planting densities can lead to inflated group differences and may confound genotypes' competitive ability and genetically underpinned variation. Synthesis. We propose that spatially explicit models can help avoid biased results by informing the design and analysis of field-based transplant garden experiments. Alternately, including neighborhood effects in post hoc analyses of transplant garden experiments is likely to provide novel insights into the roles of biotic factors and density dependence in genetic differentiation.

Ecology and Evolution↗

USGS2022

Assessing population genomic structure and polyploidy: A crucial step for native plant restoration

Establishing an effective restoration program requires baseline genetic information to make sound decisions for seed increase and transfer. For many plants this information is lacking, especially among native forbs that are critical for pollinator health. Erigeron speciosus is a widespread, perennial forb occupying montane environments in the western United States and Canada. This species is important in fostering pollinator diversity. Our study examines the population genetic patterns across the species range using reduced-representation sequencing and surveys for genome duplication using flow cytometry and cytology. These genomic tools provide critical information for seed increase and seed transfer, necessary for restoration programs. Population genetic differentiation ( F ST ) average was 0.13 and ranged from 0.05 to 0.24 among 23 collection sites. Model-based Bayesian clustering supported a model with collection sites grouped into two populations, occupying distinct geographic regions of this species range. A genetic distance-based neighbor-joining tree also supported this division. Flow cytometry of 53 samples from 17 populations had 2C values that ranged from 1.7 to 3.6 pg with a mean 2C value of 2.3 pg. Putative triploids were found in two individuals from one collection site. The spatial distribution of genetic structure supports regionally based taxonomic descriptions of two varieties: speciosus in the North and macranthus in the South. This assessment of genetic structure and genome duplication describes an effective approach in developing baseline genetic information for restoration species, especially those species that may harbor complex taxonomy and polyploidy.

Colorado, Idaho, Montana, Oregon, South Dakota, Ut↗

USGS2022

A haploid pseudo-chromosome genome assembly for a keystone sagebrush species of western North American rangelands

Increased ecological disturbances, species invasions, and climate change are creating severe conservation problems for several plant species that are widespread and foundational. Understanding the genetic diversity of these species and how it relates to adaptation to these stressors are necessary for guiding conservation and restoration efforts. This need is particularly acute for big sagebrush ( Artemisia tridentata ; Asteraceae), which was once the dominant shrub over 1,000,000 km 2 in western North America but has since retracted by half and thus has become the target of one of the largest restoration seeding efforts globally. Here, we present the first reference-quality genome assembly for an ecologically important subspecies of big sagebrush ( A. tridentata subsp. tridentata ) based on short and long reads, as well as chromatin proximity ligation data analyzed using the HiRise pipeline. The final 4.2-Gb assembly consists of 5,492 scaffolds, with nine pseudo-chromosomal scaffolds (nine scaffolds comprising at least 90% of the assembled genome; n = 9). The assembly contains an estimated 43,377 genes based on ab initio gene discovery and transcriptional data analyzed using the MAKER pipeline, with 91.37% of BUSCOs being completely assembled. The final assembly was highly repetitive, with repeat elements comprising 77.99% of the genome, making the Artemisia tridentata subsp. tridentata genome one of the most highly repetitive plant genomes to be sequenced and assembled. This genome assembly advances studies on plant adaptation to drought and heat stress and provides a valuable tool for future genomic research.

Arizona, California, Colorado, Idaho, Montana, Neb↗

USGS2020

Assessment of population genetics and climatic variability can refine climate‐informed seed transfer guidelines

Restoration guidelines increasingly recognize the importance of genetic attributes in translocating native plant materials (NPMs). However, when species‐specific genetic information is unavailable, seed transfer guidelines use climate‐informed seed transfer zones (CSTZs) as an approximation. While CSTZs may improve how NPMs are developed and/or matched to restoration sites, they overlook genetic factors that can diminish restoration success and/or deteriorate natural patterns of genetic diversity and environmental factors that may introduce unexpected variation. Here, we analyze molecular data and geographic patterns of environmental variability across the western United States and demonstrate how they can refine CSTZs. Using genetic data available for 13 relevant plant species, we found that the probability of mixing genetically differentiated individuals (i.e. from different evolutionary lineages, or populations) was approximately 8% when considering locations separated by 50 km and reached nearly 80% by 500 km, which are distances relevant to ecoregionally constrained CSTZs. Furthermore, climate analyses revealed that geographically proximate locations are likely to maintain environmental similarity, regardless of CSTZ or ecoregion assignment. These results suggest constraining CSTZ‐informed seed transfer decisions by distance may mitigate the opportunity for negative genetic outcomes. Furthermore, environmental variability and/or specificity of NPMs (depending upon the restoration strategy) should be achieved by sourcing NPMs from geographically proximate locations to avoid introducing excessive genetic differentiation. Our results highlight the utility of combining molecular genetic data with other genetic inferences (i.e. of adaptation) to determine how best to transfer seed across restoration species' ranges and develop new restoration materials.

Restoration Ecology↗

USGS2020

Intraspecific variation in surface water uptake in a perennial desert shrub

Despite broad recognition that water is a major limiting factor in arid ecosystems, we lack an empirical understanding of how this resource is shared and distributed among neighbouring plants. Intraspecific variability can further contribute to this variation via divergent life‐history traits, including root architecture. We investigated these questions in the shrub Artemisia tridentata and hypothesized that the ability to access and utilize surface water varies among subspecies and cytotypes. We used an isotope tracer to quantify below‐ground zone of influence in A. tridentata , and tested whether spatial neighbourhood characteristics can alter plant water uptake. We introduced deuterium‐enriched water to the soil in plant interspaces in a common garden experiment and measured deuterium composition of plant stems. We then applied spatially explicit models to test for differential water uptake by A. tridentata , including intermingled populations of three subspecies and two ploidy levels. The results suggest that lateral root functioning in A. tridentata is associated with intraspecific identity and ploidy level. Subspecies adapted to habitats with deep soils generally had a smaller horizontal reach, and polyploid cytotypes were associated with greater water uptake compared to their diploid variants. We also found that plant crown volume was a weak predictor of water uptake, and that neighbourhood crowding had no discernable effect on water uptake. Intraspecific variation in lateral root functioning can lead to differential patterns of resource acquisition, an essential process in arid ecosystems in the contexts of changing climate and seasonal patterns of precipitation. Altogether, we found that lateral root development and activity are more strongly related to genetic variability within A. tridentata than to plant size. Our study highlights how intraspecific variation in life strategies is linked to mechanisms of resource acquisition.

Functional Ecology↗

USGS2019

Freezing resistance, safety margins, and survival vary among big sagebrush populations across the western United States

Premise Physiological responses to temperature extremes are considered strong drivers of species’ demographic responses to climate variability. Plants are typically classified as either avoiders or tolerators in their freezing‐resistance mechanism, but a gradient of physiological‐threshold freezing responses may exist among individuals of a species. Moreover, adaptive significance of physiological freezing responses is poorly characterized, particularly under warming conditions that relax selection on cold hardiness. Methods Freezing responses were measured in winter and again for new foliage in spring for 14 populations of Artemisia tridentata collected throughout its range and planted in a warm common garden. The relationships of the freezing responses to survival were evaluated in the warm garden and in two colder gardens. Results Winter and spring freezing resistance were not correlated and appeared to be under differing selection regimes, as evident in correlations with different population climate of origin variables. All populations resisted considerably lower temperatures in winter than in spring, with populations from more continental climates showing narrower freezing safety margins (difference in temperatures at which ice‐nucleation occurs and 50% reduction in chlorophyll fluorescence occurs) in spring. Populations with greater winter freezing resistance had lower survivorship in the warmest garden, while populations with greater spring freezing resistance had lower survivorship in a colder garden. Conclusions These survivorship patterns relative to physiological thresholds suggest excess freezing resistance may incur a survival cost that likely relates to a trade‐off between carbon gain and freezing resistance during critical periods of moisture availability. This cost has implications for seed moved from cooler to warmer environments and for plants growing in warming environments.

American Journal of Botany↗

USGS2018

Population history provides foundational knowledge for utilizing and developing native plant restoration materials

A species’ population structure and history are critical pieces of information that can help guide the use of available native plant materials in restoration treatments and decide what new native plant materials should be developed to meet future restoration needs. In the western United States, Pseudoroegneria spicata (bluebunch wheatgrass; Poaceae) is an important component of grassland and shrubland plant communities and commonly used for restoration due to its drought resistance and competitiveness with exotic weeds. We used next‐generation sequencing data to investigate the processes that shaped P. spicata 's geographic pattern of genetic variation across the Intermountain West. Pseudoroegneria spicata 's genetic diversity is partitioned into populations that likely differentiated since the Last Glacial Maximum. Adjacent populations display varying magnitudes of historical gene flow, with migration rates ranging from multiple migrants per generation to multiple generations per migrant. When considering the commercial germplasm sources available for restoration, genetic identities remain representative of the wildland localities from which germplasm sources were originally developed, and they maintain high levels of heterozygosity and nucleotide diversity. However, the commercial germplasm sources represent a small fraction of the overall genetic diversity of P. spicata in the Intermountain West. Given the low migration rates and long divergence times between some pairs of P. spicata populations, using commercial germplasm sources could facilitate undesirable restoration outcomes when used in certain geographic areas, even if the environment in which the commercial materials thrive is similar to that of the restoration site. As such, population structure and history can be used to provide guidance on what geographic areas may need additional native plant materials so that restoration efforts support species and community resilience and improve outcomes.

Evolutionary Applications↗

USGS2018

Beyond traditional ecological restoration on the Colorado Plateau

The Colorado Plateau is one of North America's five major deserts, encompassing 340,000 km 2 of the western U.S., and offering many opportunities for restoration relevant to researchers and land managers in drylands around the globe. The Colorado Plateau is comprised of vast tracts of public land managed by local, state, and federal agencies that oversee a wide range of activities (e.g., mineral and energy extraction, livestock grazing, and recreation). About 75% of the Plateau is managed by federal and tribal agencies and tens of millions of people visit the Plateau's public lands each year. However, even in the face of this diverse use, our knowledge of effective ways to restore Plateau ecosystems remains relatively poor. Further, the multiple agencies on the Plateau have mandates that differ greatly in allowable practices, restoration needs, and desired outcomes. The Colorado Plateau is also expected to undergo ecosystem shifts in the face of climate change, further complicating management decisions and potentially limiting some options while creating others. Here we explore the current state of Colorado Plateau restoration science and underscore key challenges and opportunities for improving our capacity to maintain the myriad of services provided by these desert ecosystems. We highlight past research efforts and future needs related to restoration concepts, including consideration and design of novel ecosystems, mitigation for and adaptation to climate change, use of genetically diverse seed adapted for current and future conditions, and the value of strong multi‐agency and stakeholder collaborations in restoring systems on the Colorado Plateau and beyond.

Colorado Plateau↗

USGS2017

Climate drives adaptive genetic responses associated with survival in big sagebrush (Artemisia tridentata)

A genecological approach was used to explore genetic variation for survival in Artemisia tridentata (big sagebrush). Artemisia tridentata is a widespread and foundational shrub species in western North America. This species has become extremely fragmented, to the detriment of dependent wildlife, and efforts to restore it are now a land management priority. Common-garden experiments were established at three sites with seedlings from 55 source-populations. Populations included each of the three predominant subspecies, and cytotype variations. Survival was monitored for 5 years to assess differences in survival between gardens and populations. We found evidence of adaptive genetic variation for survival. Survival within gardens differed by source-population and a substantial proportion of this variation was explained by seed climate of origin. Plants from areas with the coldest winters had the highest levels of survival, while populations from warmer and drier sites had the lowest levels of survival. Survival was lowest, 36%, in the garden that was prone to the lowest minimum temperatures. These results suggest the importance of climatic driven genetic differences and their effect on survival. Understanding how genetic variation is arrayed across the landscape, and its association with climate can greatly enhance the success of restoration and conservation.

Evolutionary Applications↗

USGS2016

Climate adaption and post-fire restoration of a foundational perennial in cold desert: Insights from intraspecific variation in response to weather

1.The loss of foundational but fire-intolerant perennials such as sagebrush due to increases in fire size and frequency in semiarid regions has motivated efforts to restore them, often with mixed or even no success. Seeds of sagebrush Artemisia tridentata and related species must be moved considerable distances from seed source to planting sites, but such transfers have not been guided by an understanding of local climate adaptation. Initial seedling establishment and its response to weather are a key demographic bottleneck that likely varies among subspecies and populations of sagebrush. 2.We assessed differences in survival, growth, and physiological responses of sagebrush to weather among eleven seed sources that varied in subspecies, cytotype, and climates-of-origin over 18 months following outplanting. Diploid or polyploid populations of mountain, Wyoming, and basin big sagebrush ( A.tridentata ssp. vaseyana, A.tridentata ssp. wyomingensis, and A.tridentata ssp. tridentata , respectively) were planted onto five burned sites that normally support A.t.wyomingensis with some A.t.tridentata . 3.A.t.wyomingensis had the most growth and survival, and tetraploid populations had greater survival and height than diploids. Seasonal timing of mortality varied among the subspecies/cytotypes and was more closely related to minimum temperatures than water deficit. 4.Temperatures required to induce ice formation were up to 6°C more negative in 4n- A.t.tridentata and A.t.wyomingensis than other subspecies/cytotypes, indicating greater freezing avoidance. In contrast, freezing resistance of photosynthesis varied only 1°C among subspecies/cytotypes, being greatest in A.t.wyomingensis and least in the subspecies normally considered most cold-adapted, A.t.vaseyana . A large spectrum of reliance on freezing-avoidance vs. freezing-tolerance was observed and corresponded to differences in post-fire survivorship among subspecies/cytotypes. Differences in water deficit responses among subspecies/cytotypes were not as strong and did not relate to survival patterns. 5. Synthesis and applications. Low temperature responses are a key axis defining climate adaptation in young sagebrush seedlings and vary more with cytotype than with subspecies, which contrasts with the traditional emphases on (i) water limitations to explain establishment in these deserts, and (ii) subspecies in selecting restoration seedings. These important and novel insights on climate adaptation are critical for seed selection and parameterizing seed transfer zones, and were made possible by incorporating weather data with survival statistics. The survival/weather statistics used here could be applied to any restoration planting or seeding to help elucidate factors contributing to success and enable adaptive management.

Journal of Applied Ecology↗

USGS2016

The integrated rangeland fire management strategy actionable science plan

The Integrated Rangeland Fire Management Strategy (hereafter Strategy, DOI 2015) outlined the need for coordinated, science-based adaptive management to achieve long-term protection, conservation, and restoration of the sagebrush (Artemisia spp.) ecosystem. A key component of this management approach is the identification of knowledge gaps that limit implementation of effective strategies to meet current management challenges. The tasks and actions identified in the Strategy address several broad topics related to management of the sagebrush ecosystem. This science plan is organized around these topics and specifically focuses on fire, invasive plant species and their effects on altering fire regimes, restoration, sagebrush and greater sage-grouse (Centrocercus urophasianus), and climate and weather.

Report↗

USGS2015

Blackbrush ( Coleogyne ramosissima Torr. ): State of our knowledge and future challenges

Covering 130,000 square miles and a wide range of elevations from desert to alpine in Arizona, Utah, Colorado, and New Mexico, the Colorado Plateau has long fascinated researchers. The Colorado Plateau VI provides readers with a plethora of updates and insights into land conservation and management questions currently surrounding the region. The Colorado Plateau VI’s contributors show how new technologies for monitoring, spatial analysis, restoration, and collaboration improve our understanding, management, and conservation of outcomes at the appropriate landscape scale for the Colorado Plateau. The volume’s chapters fall into five major themes: monitoring as a key tool for addressing management challenges, restoration approaches to improving ecosystem condition and function, collaboration and organizational innovations to achieve conservation and management objectives, landscape-scale approaches to understanding, and managing key species and ecological communities. Focusing on the integration of science into resource management issues over the Colorado Plateau, this volume includes contributions from dozens of leading scholars of the region. The Colorado Plateau VI proves a valuable resource to all interested in the conservation management, natural history, and cultural biological resources of the Colorado Plateau.

Arizona, Colorado, New Mexico, Utah↗

USGS2014

Adaptive responses reveal contemporary and future ecotypes in a desert shrub

Interacting threats to ecosystem function, including climate change, wildfire, and invasive species necessitate native plant restoration in desert ecosystems. However, native plant restoration efforts often remain unguided by ecological genetic information. Given that many ecosystems are in flux from climate change, restoration plans need to account for both contemporary and future climates when choosing seed sources. In this study we analyze vegetative responses, including mortality, growth, and carbon isotope ratios in two blackbrush (Coleogyne ramosissima) common gardens that included 26 populations from a range-wide collection. This shrub occupies ecotones between the warm and cold deserts of Mojave and Colorado Plateau ecoregions in western North America. The variation observed in the vegetative responses of blackbrush populations was principally explained by grouping populations by ecoregions and by regression with site-specific climate variables. Aridity weighted by winter minimum temperatures best explained vegetative responses; Colorado Plateau sites were usually colder and drier than Mojave sites. The relationship between climate and vegetative response was mapped within the boundaries of the species–climate space projected for the contemporary climate and for the decade surrounding 2060. The mapped ecological genetic pattern showed that genetic variation could be classified into cool-adapted and warm-adapted ecotypes, with populations often separated by steep clines. These transitions are predicted to occur in both the Mojave Desert and Colorado Plateau ecoregions. While under contemporary conditions the warm-adapted ecotype occupies the majority of climate space, climate projections predict that the cool-adapted ecotype could prevail as the dominant ecotype as the climate space of blackbrush expands into higher elevations and latitudes. This study provides the framework for delineating climate change-responsive seed transfer guidelines, which are needed to inform restoration and management planning. We propose four transfer zones in blackbrush that correspond to areas currently dominated by cool-adapted and warm-adapted ecotypes in each of the two ecoregions.

Arizona;California;Colorado;Nevada;New Mexico;Utah↗