An official website of the United States government
Abstract Understanding how vegetation responds to drought is fundamental for understanding the broader implications of climate change on foundation tree species that support high biodiversity. Leveraging remote sensing technology provides a unique vantage point to explore these responses across and within species.We investigated interspecific drought responses of twoPopulusspecies (P.fremontii,P.angustifolia) and their naturally occurring hybrids using leaf‐level visible through shortwave infrared (VSWIR; 400–2500 nm) reflectance. AsF1hybrids backcross with either species, resulting in a range of backcross genotypes, we heretofore refer to the two species and their hybrids collectively as ‘cross types’. We additionally explored intraspecific variation inP. fremontiidrought response at the leaf and canopy levels using reflectance data and thermal unmanned aerial vehicle (UAV) imagery. We employed several analyses to assess genotype‐by‐environment (G × E) interactions concerning drought, including principal component analysis, support vector machine and spectral similarity index.Five key findings emerged: (1) Spectra of all three cross types shifted significantly in response to drought. The magnitude of these reaction norms can be ranked from hybrids>P. fremontii>P. angustifolia, suggesting differential variation in response to drought; (2) Spectral space among cross types constricted under drought, indicating spectral—and phenotypic—convergence; (3) Experimentally, populations ofP. fremontiifrom cool regions had different responses to drought than populations from warm regions, with source population mean annual temperature driving the magnitude and direction of change in VSWIR reflectance. (4) UAV thermal imagery revealed that watered, warm‐adapted populations maintained lower leaf temperatures and retained more leaves than cool‐adapted populations, but differences in leaf retention decreased when droughted. (5) These findings are consistent with patterns of local adaptation to drought and temperature stress, demonstrating the ability of leaf spectra to detect ecological and evolutionary responses to drought as a function of adaptation to different environments.Synthesis.Leaf‐level spectroscopy and canopy‐level UAV thermal data captured inter‐ and intraspecific responses to water stress in cottonwoods, which are widely distributed in arid environments. This study demonstrates the potential of remote sensing to monitor and predict the impacts of drought on scales varying from leaves to landscapes.
more »
« less
Remote sensing of ploidy level in quaking aspen ( Populus tremuloides Michx.)
Abstract Ploidy level in plants may influence ecological functioning, demography and response to climate change. However, measuring ploidy level typically requires intensive cell or molecular methods.We map ploidy level variation in quaking aspen, a dominant North American tree species that can be diploid or triploid and that grows in spatially extensive clones. We identify the predictors and spatial scale of ploidy level variation using a combination of genetic and ground‐based and airborne remote sensing methods.We show that ground‐based leaf spectra and airborne canopy spectra can both classify aspen by ploidy level with a precision‐recall harmonic mean of 0.75–0.95 and Cohen's kappa ofc.0.6–0.9. Ground‐based bark spectra cannot classify ploidy level better than chance. We also found that diploids are more common on higher elevation and steeper sites in a network of forest plots in Colorado, and that ploidy level distribution varies at subkilometer spatial scales.Synthesis. Our proof‐of‐concept study shows that remote sensing of ploidy level could become feasible in this tree species. Mapping ploidy level across landscapes could provide insights into the genetic basis of species' responses to climate change.
more »
« less
- PAR ID:
- 10372292
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 108
- Issue:
- 1
- ISSN:
- 0022-0477
- Page Range / eLocation ID:
- p. 175-188
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Climate change is stressing many forests around the globe, yet some tree species may be able to persist through acclimation and adaptation to new environmental conditions. The ability of a tree to acclimate during its lifetime through changes in physiology and functional traits, defined here as its acclimation potential, is not well known.We investigated the acclimation potential of trembling aspenPopulus tremuloidesand ponderosa pinePinus ponderosatrees by examining within‐species variation in drought response functional traits across both space and time, and how trait variation influences drought‐induced tree mortality. We measured xylem tension, morphological traits and physiological traits on mature trees in southwestern Colorado, USA across a climate gradient that spanned the distribution limits of each species and 3 years with large differences in climate.Trembling aspen functional traits showed high within‐species variation, and osmotic adjustment and carbon isotope discrimination were key determinants for increased drought tolerance in dry sites and in dry years. However, trembling aspen trees at low elevation were pushed past their drought tolerance limit during the severe 2018 drought year, as elevated mortality occurred. Higher specific leaf area during drought was correlated with higher percentages of canopy dieback the following year. Ponderosa pine functional traits showed less within‐species variation, though osmotic adjustment was also a key mechanism for increased drought tolerance. Remarkably, almost all traits varied more year‐to‐year than across elevation in both species.Our results shed light on the scope and limits of intraspecific trait variation for mediating drought responses in key southwestern US tree species and will help improve our ability to model and predict forest responses to climate change. Read the freePlain Language Summaryfor this article on the Journal blog.more » « less
-
Summary Plastic responses of plants to their environment vary as a result of genetic differentiation within and among species. To accurately predict rangewide responses to climate change, it is necessary to characterize genotype‐specific reaction norms across the continuum of historic and future climate conditions comprising a species' range.The North American hybrid zone ofPopulus trichocarpaandPopulus balsamiferarepresents a natural system that has been shaped by climate, geography, and introgression. We leverage a dataset containing 44 clonal genotypes from this natural hybrid zone, planted across 17 replicated common garden experiments spanning a broad climatic range. Growth and mortality were measured over 2 yr, enabling us to model reaction norms for each genotype across these tested environments.Species ancestry and intraspecific genomic variation significantly influenced growth across environments, with genotypic variation in reaction norms reflecting a trade‐off between cold tolerance and growth. Using modeled reaction norms for each genotype, we predicted that genotypes with moreP. trichocarpaancestry may gain an advantage under warmer climates.Spatial shifts of the hybrid zone could facilitate the spread of beneficial alleles into novel climates. These results highlight that genotypic variation in responses to temperature will have landscape‐level effects.more » « less
-
Summary Genetic load can reduce fitness and hinder adaptation. While its genetic underpinnings are well established, the influence of environmental variation on genetic load is less well characterized, as is the relationship between genetic load and putatively adaptive genetic variation. This study examines the interplay among climate, species range dynamics, adaptive variation, and mutational load – a genomic measure of genetic load – inVitis arizonica, a wild grape native to the American Southwest.We estimated mutational load and identified climate‐associated adaptive genetic variants in 162 individuals across the species' range. Using a random forest model, we analyzed the relationship between mutational load, climate, and range shifts.Our findings linked mutational load to climatic variation, historical dispersion, and heterozygosity. Populations at the leading edge of range expansion harbored higher load and fewer putatively adaptive alleles associated with climate. Climate projections suggest thatV. arizonicawill expand its range by the end of the century, accompanied by a slight increase in mutational load at the population level.This study advances understanding of how environmental and geographic factors shape genetic load and adaptation, highlighting the need to integrate deleterious variation into broader models of species response to climate change.more » « less
-
Summary Whole‐genome duplications, widely observed in plant lineages, have significant evolutionary and ecological impacts. Yet, our current understanding of the direct implications of ploidy shifts on short‐ and long‐term plant evolution remains fragmentary, necessitating further investigations across multiple ploidy levels.Chlamydomonas reinhardtiiis a valuable model organism with profound potential to study the impact of ploidy increase on the longer term in a laboratory environment. This is partly due to the ability to increase the ploidy level.We developed a strategy to engineer ploidy inC. reinhardtiiusing noninterfering, antibiotic, selectable markers. This approach allows us to induce higher ploidy levels inC. reinhardtiiand is applicable to field isolates, which expands beyond specific auxotroph laboratory strains and broadens the genetic diversity of parental haploid strains that can be crossed. We implement flow cytometry for precise measurement of the genome size of strains of different ploidy.We demonstrate the creation of diploids, triploids, and tetraploids by engineering North American field isolates, broadening the application of synthetic biology principles inC. reinhardtii. However, our newly formed triploids and tetraploids show signs of rapid aneuploidization.Our study greatly facilitates the application ofC. reinhardtiito study polyploidy, in both fundamental and applied settings.more » « less
