Biology subjects

Agneray, A. C.

Publications and source records attributed to Agneray, A. C..

7 recordsLinked to original sources

bioRxiv2023

Environment predicts the maintenance of reproductive isolation in a mosaic hybrid zone of rubber rabbitbrush

Widely distributed plants of western North America experience divergent selection across environmental gradients, have complex histories shaped by biogeographic barriers and distributional shifts, and often illustrate continuums of reproductive isolation. Rubber rabbitbrush (Ericameria nauseosa) is a foundational shrub species that occurs across diverse environments of western North America. Its remarkable phenotypic diversity is currently ascribed to two subspecies - E. n. nauseosa and E. n. consimilis - and 22 named varieties. We analyzed how genetic variation is partitioned across subspecies, varieties, and environment using high throughput sequencing of reduced representation libraries. We found clear evidence for divergence between the two subspecies, despite largely sympatric distributions. Numerous locations exhibiting admixed ancestry were not geographically localized but were widely distributed across a mosaic hybrid zone. The occurrence of hybrid and subspecific ancestries was strongly predicted by environmental variables as well as the proximity to major ecotones between ecoregions. Although this repeatability illustrates the importance of environmental factors in shaping reproductive isolation, variability in the outcomes of hybridization also indicated these factors likely differ across ecological contexts. There was mixed evidence for the evolutionary cohesiveness of varieties, but several genetically distinct and narrow endemic varieties exhibited admixed subspecific ancestries, hinting at the possibility for transgressive hybridization to contribute to phenotypic novelty and the colonization of new environments in E. nauseosa.

evolutionary biology↗

bioRxiv2022

Does a history of co-occurrence predict plant performance, community productivity, or invasion resistance?

A history of species co-occurrence in plant communities is hypothesized to lead to greater niche differentiation, more efficient resource partitioning, and more productive, resistant communities as a result of evolution in response to biotic interactions. We asked if individual species or community responses differed when communities were founded with species sharing a history of co-occurrence (sympatric) or with species originating from different locations (allopatric). Using shrub, grass, and forb species from six locations in the western Great Basin, USA, we compared establishment, productivity, reproduction, phenology, and resistance to invaders for experimental communities with either sympatric or allopatric associations. Each community type was planted with six taxa in outdoor mesocosms, measured over three growing seasons, and invaded with the annual grass Bromus tectorum in the final season. For most populations, the allopatric or sympatric status of neighbors was not important. However, in some cases it was beneficial for some species from some locations to be planted with allopatric neighbors, while others benefited from sympatric neighbors, and some of these responses had large effects. For instance, the Elymus population that benefited the most from allopatry grew 50% larger with allopatric neighbors than in single origin mesocosms. This response affected invasion resistance, as B. tectorum biomass was strongly affected by productivity and phenology of Elymus spp., as well as Poa secunda. Our results demonstrate that while community composition can in some cases affect plant performance in semi-arid plant communities, assembling sympatric communities is not sufficient to ensure high ecosystem services. Instead, we observed a potential interaction between sampling effects and evolutionary history that can create invasion resistant allopatric communities.

ecology↗

bioRxiv2022

Not all seed transfer zones are created equal: Using fire history to identify seed needs in the Cold Deserts of the Western US

Restoration planning requires a reliable seed supply, yet many projects occur in response to unplanned events. Identifying regions of greater risk could help guide seed procurement. Using fire perimeters (2000-2019), we investigated differences in fire occurrence (frequency, area burned, percent of area burned) among seed transfer zones within Cold Deserts of the US. We considered both provisional seed transfer zones (PSTZs), created using climate and stratified by ecoregion, and empirical seed transfer zones (ESTZs) for two species commonly used in restoration. Finally, we present a case study on fire occurrence within Northern Basin and Range greater sage-grouse Priority Areas for Conservation (PACs). Historic fire was effective for prioritizing seed zones: 23 of 132 PSTZs burned every year, and, within each ecoregion, two PSTZs comprised [greater double equals] 50% of the total area burned across all years. Similarly, fire disproportionately occurred in some ESTZs; in the Northern Basin and Range, one (Artemisia tridentata - 83%) or two zones (Pseudoroegneria spicata - 65%) made up a majority of total area burned. Fire occurrence within PACs largely reflected the PSTZ and ESTZ priorities found for the ecoregion, with small exceptions. Imperiled PSTZs (high proportion burned) in PACs largely reflected the patterns found across the ecoregion, while imperiled ESTZs departed from ecoregional patterns. Considering historic disturbance can focus seed procurement efforts on regions that encounter regular disturbance, experience large disturbances, or have particular conservation value. This information can guide seed production, purchase, and storage, create more certainty for growers and managers, and ultimately increase restoration success. IMPLICATIONS FOR PRACTICEO_LIAvailable data on past disturbance patterns may inform strategies for prioritizing seed procurement decisions, especially as geospatial information becomes more widely available C_LIO_LIThe methods presented here illustrate an approach for using historic disturbance data to identify regions that are of greatest need for seed collection and conservation, using seed transfer zones within US Cold Desert ecoregions as an example C_LIO_LIIdentifying regions that experience disturbance over large areas or are likely to be imperiled due to disturbance at a high proportion can guide the collection and conservation of plant materials and better align available plant material with future restoration needs C_LI

ecology↗

bioRxiv2022

Fine-scale spatial genetic structure in a locally abundant native bunchgrass (Achnatherum thurberianum) including distinct lineages revealed within seed transfer zones

Analyses of the factors shaping spatial genetic structure in widespread plant species are important for understanding evolutionary history and local adaptation and have applied significance for guiding conservation and restoration decisions. Thurbers needlegrass (Achnatherum thurberianum) is a widespread, locally abundant grass that inhabits heterogeneous arid environments of western North America and is of restoration significance. It is a common component of shrubland steppe communities in the Great Basin Desert, where drought, fire, and invasive grasses have degraded natural communities. Using a reduced representation sequencing approach, we generated SNP data at 5,677 loci across 246 individuals from 17 A. thurberianum populations spanning five previously delineated seed zones from the western Great Basin. Analyses revealed pronounced population genetic structure, with individuals forming consistent geographical clusters across a variety of population genetic analyses and spatial scales. Low levels of genetic diversity within populations, as well as high population estimates of linkage disequilibrium and inbreeding, were consistent with self-fertilization as a contributor to population differentiation. Moreover, variance partitioning and partial RDA indicated local adaptation to the environment as an additional factor influencing the spatial distribution of genetic variation. The environmental variables driving these results were similar to those implicated in recent genecological work which inferred local adaptation in order to delineate seed zones. However, our analyses also reveal a complex evolutionary history of A. thurberanium in the Great Basin, where previously delineated seed zones contain distantly related populations. Overall, our results indicate that numerous factors shape genetic variation in A. thurberianum and that evolutionary history, along with differentiation across distinct geographic and environmental scales, should be considered for conservation and restoration plans.

evolutionary biology↗

bioRxiv2021

Genomic and common garden approaches yield complementary results for quantifying environmental drivers of local adaptation in rubber rabbitbrush, a foundational Great Basin shrub

The spatial structure of genomic and phenotypic variation across populations reflects historical and demographic processes as well as evolution via natural selection. Characterizing such variation can provide an important perspective for understanding the evolutionary consequences of changing climate and for guiding ecological restoration. While evidence for local adaptation has been traditionally evaluated using phenotypic data, modern methods for generating and analyzing landscape genomic data can directly quantify local adaptation by associating allelic variation with environmental variation. Here, we analyze both genomic and phenotypic variation of rubber rabbitbrush (Ericameria nauseosa), a foundational shrub species of western North America. To quantify landscape genomic structure and provide perspective on patterns of local adaptation, we generated reduced representation sequencing data for 17 wild populations (222 individuals; 38,615 loci) spanning a range of environmental conditions. Population genetic analyses illustrated pronounced landscape genomic structure jointly shaped by geography and environment. Genetic-environment association (GEA) analyses using both redundancy analysis (RDA) and a machine-learning approach (Gradient Forest) indicated environmental variables (precipitation seasonality, slope, aspect, elevation, and annual precipitation) influenced spatial genomic structure, and were correlated with allele frequency shifts indicative of local adaptation at a consistent set of genomic regions. We compared our GEA based inference of local adaptation with phenotypic data collected by growing seeds from each population in a greenhouse common garden. Population differentiation in seed weight, emergence, and seedling traits was associated with environmental variables (e.g., precipitation seasonality) that were also implicated in GEA analyses, suggesting complementary conclusions about the drivers of local adaptation across different methods and data sources. Our results provide a baseline understanding of spatial genomic structure for E. nauseosa across the western Great Basin and illustrate the utility of GEA analyses for detecting the environmental causes and genetic signatures of local adaptation in a widely distributed plant species of restoration significance.

evolutionary biology↗

bioRxiv2020

Using seedling phenotypic traits to select local seed sources for large-scale restoration: methods and outcomes in a Great Basin case study

Establishing plants from seed is often a limitation to restoration success in semi-arid systems. For restoration purposes, managers can either use widely-available commercial seeds, which are often sourced from far outside the seeding area, or take extra steps to use locally collected seeds. If local seeds have traits more conducive to seedling establishment in degraded sites, they could increase restoration success. Here, we asked whether wild-collected seeds of two native perennial grasses, Elymus elymoides and Poa secunda, had more favorable characteristics than commercial sources. Seeds were collected from four populations within the Winnemucca District of the Nevada Bureau of Land Management, which manages lands within the Great Basin, US. Collections were screened for seed and seedling characteristics associated with increased plant performance in invaded Great Basin systems, and we provide a detailed methodology for these measurements. Relative to commercial seeds, wild-collected seeds had more characteristics identified as beneficial for seedling establishment including earlier emergence, higher specific root length, more root tips, and smaller overall size (E. elymoides), and earlier emergence, longer roots, higher root mass ratio, and more root tips (P. secunda). Commercial sources had significantly larger seeds than wild populations, a trait that had mixed effects on performance in previous research, and one that may change as wild collections are increased in agronomic conditions. These results suggest that locally-sourced populations are more likely to perform well in invaded areas, providing support for efforts to collect, screen, and increase local sources of seeds to improve restoration success. Implications for PracticeO_LICollecting and increasing local seeds requires more time and effort than purchasing commercially-available seeds, but if these sources have a greater chance at surviving in restoration sites, this effort is warranted C_LIO_LIIn our study, remnant local populations possessed more potentially adaptive traits than commercially-available alternatives, indicating they may be superior sources for the restoration of disturbed sites in their local regions C_LIO_LIScreening multiple seed sources for potentially adaptive seed and seedling traits can be a relatively quick and effective way to select the most promising seeds for increase C_LI

ecology↗

bioRxiv2018

Strong Patterns of Intraspecific Variation and Local Adaptation in Great Basin Plants Revealed Through a Review of 75 Years of Experiments

Variation in natural selection across heterogenous landscapes often produces 1) among-population differences in phenotypic traits, 2) trait-by-environment associations, and 3) higher fitness of local populations. Using a broad literature search, we documented the frequency of these three signatures in plants native to North Americas Great Basin and asked which traits and environmental variables were involved. We also asked, independent of geographic distance, whether populations from more similar environments had more similar traits. From 327 experiments testing 121 taxa in 170 studies, we found 95.1% of 305 experiments reported among-population differences, and 81.4% of 161 experiments reported trait-by-environment associations. Locals showed greater survival in 67% of 24 reciprocal experiments that reported survival, and higher fitness in 90% of 10 reciprocal experiments that reported reproductive output. Variation in eight commonly-measured traits was associated with mean annual precipitation and mean annual temperature at the source location, with notably strong relationships for flowering phenology, leaf size, and survival, among others. Although the Great Basin is sometimes perceived as environmentally homogenous, our results demonstrate widespread habitat-related population differentiation and local adaptation, suggesting that locally-sourced plants likely harbor restoration-relevant adaptations, and that certain key traits and environmental variables should be prioritized in future assessments of plants.

ecology↗