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  • 1
    In: Functional Ecology, Wiley, Vol. 33, No. 11 ( 2019-11), p. 2105-2115
    Abstract: Expression of herbivore defense traits can change dramatically during the course of plant development. Little is known, however, about the degree of genetic or sexual variation in these ontogenetic defense trajectories or whether the trajectories themselves are adaptive, especially in long‐lived species. We used a 13‐year dataset of chemical defense traits, growth and survivorship from a common garden of trembling aspen ( Populus tremuloides ) genotypes to document long‐term defense trajectories and their relationship to tree fitness during juvenile and early mature stages. Overall, concentrations of the two principal classes of aspen defense compounds (salicinoid phenolic glycosides [SPGs] and condensed tannins [CTs] ) decreased to differing degrees in foliage of juvenile trees and then remained relatively constant in maturity. Initial values, juvenile rates of change and average mature values all exhibited significant genetic variation for both SPGs and CTs. Relationships between defense trajectory parameters and metrics of tree fitness (growth and survivorship) depended on compound type and tree sex. Females with higher‐allocation SPG trajectories (high initial juvenile concentrations, slow juvenile declines, high mature concentrations) grew more slowly relative to females with lower‐allocation trajectories. In males, higher‐allocation SPG trajectories had a lesser effect on growth but were associated with reduced mortality. Juvenile CT trajectories were not correlated with tree fitness, but average CT concentration in maturity was positively related to growth in females. These results suggest that ontogenetic defense trajectories are adaptive and subject to natural selection. Genotypic variation and ontogeny shape tree defensive chemistry, both independently and interactively. These patterns of defense expression have the potential to structure trophic interactions and the genetic composition of forests in both space and time. A free Plain Language Summary can be found within the Supporting Information of this article.
    Type of Medium: Online Resource
    ISSN: 0269-8463 , 1365-2435
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2020307-X
    detail.hit.zdb_id: 619313-4
    SSG: 12
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  • 2
    In: New Phytologist, Wiley, Vol. 230, No. 2 ( 2021-04), p. 710-719
    Abstract: The ability to tolerate neighboring plants (i.e. degree of competitive response) is a key determinant of plant success in high‐competition environments. Plant genotypes adjust their functional trait expression under high levels of competition, which may help explain intra‐specific variation in competitive response. However, the relationships between traits and competitive response are not well understood, especially in trees. In this study, we investigated among‐genotype associations between tree trait plasticity and competitive response. We manipulated competition intensity in experimental stands of trembling aspen ( Populus tremuloides ) to address the covariance between competition‐induced changes in functional trait expression and aspects of competitive ability at the genotype level. Genotypic variation in the direction and magnitude of functional trait responses, especially those of crown foliar mass, phytochemistry, and leaf physiology, was associated with genotypic variation in competitive response. Traits exhibited distinct plastic responses to competition, with varying degrees of genotypic variation and covariance with other trait responses. The combination of genotypic diversity and covariance among functional traits led to tree responses to competition that were coordinated among traits yet variable among genotypes. Such relationships between tree traits and competitive success have the potential to shape stand‐level trait distributions over space and time.
    Type of Medium: Online Resource
    ISSN: 0028-646X , 1469-8137
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 208885-X
    detail.hit.zdb_id: 1472194-6
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  • 3
    In: Magnetic Resonance in Medicine, Wiley, Vol. 42, No. 6 ( 1999-12), p. 1159-1165
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1999
    detail.hit.zdb_id: 1493786-4
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  • 4
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 37 ( 2021-09-14)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 37 ( 2021-09-14)
    Abstract: All organisms experience fundamental conflicts between divergent metabolic processes. In plants, a pivotal conflict occurs between allocation to growth, which accelerates resource acquisition, and to defense, which protects existing tissue against herbivory. Trade-offs between growth and defense traits are not universally observed, and a central prediction of plant evolutionary ecology is that context-dependence of these trade-offs contributes to the maintenance of intraspecific variation in defense [Züst and Agrawal, Annu. Rev. Plant Biol. , 68, 513–534 (2017)]. This prediction has rarely been tested, however, and the evolutionary consequences of growth–defense trade-offs in different environments are poorly understood, especially in long-lived species [Cipollini et al. , Annual Plant Reviews (Wiley, 2014), pp. 263–307]. Here we show that intraspecific trait trade-offs, even when fixed across divergent environments, interact with competition to drive natural selection of tree genotypes corresponding to their growth–defense phenotypes. Our results show that a functional trait trade-off, when coupled with environmental variation, causes real-time divergence in the genetic architecture of tree populations in an experimental setting. Specifically, competitive selection for faster growth resulted in dominance by fast-growing tree genotypes that were poorly defended against natural enemies. This outcome is a signature example of eco-evolutionary dynamics: Competitive interactions affected microevolutionary trajectories on a timescale relevant to subsequent ecological interactions [Brunner et al. , Funct. Ecol. 33, 7–12 (2019)]. Eco-evolutionary drivers of tree growth and defense are thus critical to stand-level trait variation, which structures communities and ecosystems over expansive spatiotemporal scales.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 5
    In: Ecological Applications, Wiley, Vol. 28, No. 5 ( 2018-07), p. 1313-1324
    Abstract: A central challenge to understanding how climate anomalies, such as drought and heatwaves, impact the terrestrial carbon cycle, is quantification and scaling of spatial and temporal variation in ecosystem gross primary productivity ( GPP ). Existing empirical and model‐based satellite broadband spectra‐based products have been shown to miss critical variation in GPP . Here, we evaluate the potential of high spectral resolution (10 nm) shortwave (400–2,500 nm) imagery to better detect spatial and temporal variations in GPP across a range of ecosystems, including forests, grassland‐savannas, wetlands, and shrublands in a water‐stressed region. Estimates of GPP from eddy covariance observations were compared against airborne hyperspectral imagery, collected across California during the 2013–2014 HyspIRI airborne preparatory campaign. Observations from 19 flux towers across 23 flight campaigns (102 total image‐flux tower pairs) showed GPP to be strongly correlated to a suite of spectral wavelengths and band ratios associated with foliar physiology and chemistry. A partial least squares regression ( PLSR ) modeling approach was then used to predict GPP with higher validation accuracy (adjusted R 2  = 0.71) and low bias (0.04) compared to existing broadband approaches (e.g., adjusted R 2  = 0.68 and bias = −5.71 with the Sims et al. model). Significant wavelengths contributing to the PLSR include those previously shown to coincide with Rubisco (wavelengths 1,680, 1,740, and 2,290 nm) and V cmax (wavelengths 1,680, 1,722, 1,732, 1,760, and 2,300 nm). These results provide strong evidence that advances in satellite spectral resolution offer significant promise for improved satellite‐based monitoring of GPP variability across a diverse range of terrestrial ecosystems.
    Type of Medium: Online Resource
    ISSN: 1051-0761 , 1939-5582
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2010123-5
    SSG: 12
    SSG: 23
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  • 6
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2020
    In:  Oecologia Vol. 192, No. 4 ( 2020-04), p. 893-907
    In: Oecologia, Springer Science and Business Media LLC, Vol. 192, No. 4 ( 2020-04), p. 893-907
    Type of Medium: Online Resource
    ISSN: 0029-8549 , 1432-1939
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 1462019-4
    detail.hit.zdb_id: 123369-5
    SSG: 12
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  • 7
    In: Annals of Botany, Oxford University Press (OUP), Vol. 131, No. 1 ( 2023-02-07), p. 229-242
    Abstract: At the population level, genetic diversity is a key determinant of a tree species’ capacity to cope with stress. However, little is known about the relative importance of the different components of genetic diversity for tree stress responses. We compared how two sources of genetic diversity, genotype and cytotype (i.e. differences in ploidy levels), influence growth, phytochemical and physiological traits of Populus tremuloides in the presence and absence of environmental stress. Methods In a series of field studies, we first assessed variation in traits across diploid and triploid aspen genotypes from Utah and Wisconsin under non-stressed conditions. In two follow-up experiments, we exposed diploid and triploid aspen genotypes from Wisconsin to individual and interactive drought stress and defoliation treatments and quantified trait variations under stress. Key Results We found that (1) tree growth and associated traits did not differ significantly between ploidy levels under non-stressed conditions. Instead, variation in tree growth and most other traits was driven by genotypic and population differences. (2) Genotypic differences were critical for explaining variation of most functional traits and their responses to stress. (3) Ploidy level played a subtle role in shaping traits and trait stress responses, as its influence was typically obscured by genotypic differences. (4) As an exception to the third conclusion, we showed that triploid trees expressed 17 % higher foliar defence (tremulacin) levels, 11 % higher photosynthesis levels and 23 % higher rubisco activity under well-watered conditions. Moreover, triploid trees displayed greater drought resilience than diploids as they produced 35 % more new tissue than diploids when recovering from drought stress. Conclusion Although ploidy level can strongly influence the ecology of tree species, those effects may be relatively small in contrast to the effects of genotypic variation in highly diverse species.
    Type of Medium: Online Resource
    ISSN: 0305-7364 , 1095-8290
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1461328-1
    SSG: 12
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  • 8
    In: Journal of Ecology, Wiley, Vol. 104, No. 3 ( 2016-05), p. 850-863
    Abstract: Overbrowsing by ungulates is a major cause of poor aspen stand regeneration across North America and Eurasia. In general, factors driving ungulate browser preferences include concentrations of plant secondary compounds and the nutritional composition (non‐structural carbohydrates, protein and minerals) of foliage. While each of these phytochemical factors has been shown to independently influence ungulate preference, the relative impact of each factor is unknown, as no study to date has examined them simultaneously. Plant fitness depends not only on the capacity of plants to resist browsing, but also on their capacity to tolerate browsing once it has occurred. Little is known of aspen tolerance to browsing, which inflicts a different form of damage than insect herbivory. We employed multiple aspen genotypes, replicate trees of which were subjected to different soil nutrient treatments, to investigate: (i) the effects of aspen genotype, nutrient treatment and genotype × nutrient interactions on susceptibility to browsing by white‐tailed deer, (ii) the phytochemical basis for the patterns observed in (i), and (iii) the effects of genotype, soil nutrients and their interaction on short‐term tolerance to deer browsing. Aspen genotypes varied markedly in their vernal susceptibility to deer browsing. Genetic variation in early season levels of non‐structural carbohydrates (sugars), protein and multiple macro‐ and trace minerals had the strongest influence on tree susceptibility to browsing. In contrast, levels of phytochemical defences had minimal effects, although the range of levels expressed in this study was small. Soil nutrient availability did not significantly influence deer preference. The extent of browsing affected post‐browse tolerance across genotypes. Soil nutrient treatment had little differential effect on tolerance, and, for the most part, genotypes did not display differential tolerance to browsing, regardless of which soil nutrient treatment they experienced. Synthesis . Genetic variation for susceptibility to browsing indicates that ungulate browsers have the potential to be agents of selection in aspen populations. In contrast with previous studies in aspen highlighting the importance of phytochemical defences in shaping preferences of browsing mammals, our results indicate that the nutritional composition of foliage (sugars, protein and mineral concentrations) can have sizable effects on preference. The observed lack of influence of soil nutrient availability on tree browsing tolerance contrasts with predictions of the limiting resource model, the prevailing model for plant tolerance.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
    SSG: 12
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  • 9
    In: Cancer Epidemiology, Biomarkers & Prevention, American Association for Cancer Research (AACR), Vol. 17, No. 12 ( 2008-12-01), p. 3567-3572
    Abstract: Over 22,000 cases of ovarian cancer were diagnosed in 2007 in the United States, but only a fraction of them can be attributed to mutations in highly penetrant genes such as BRCA1. To determine whether low-penetrance genetic variants contribute to ovarian cancer risk, we genotyped 1,536 single nucleotide polymorphisms (SNP) in several candidate gene pathways in 848 epithelial ovarian cancer cases and 798 controls in the North Carolina Ovarian Cancer Study (NCO) using a customized Illumina array. The inflammation gene interleukin-18 (IL18) showed the strongest evidence for association with epithelial ovarian cancer in a gene-by-gene analysis (P = 0.002) with a & lt;25% chance of being a false-positive finding (q value = 0.240). Using a multivariate model search algorithm over 11 IL18 tagging SNPs, we found that the association was best modeled by rs1834481. Further, this SNP uniquely tagged a significantly associated IL18 haplotype and there was an increased risk of epithelial ovarian cancer per rs1834481 allele (odds ratio, 1.24; 95% confidence interval, 1.06-1.45). In a replication stage, 12 independent studies from the Ovarian Cancer Association Consortium (OCAC) genotyped rs1834481 in an additional 5,877 cases and 7,791 controls. The fixed effects estimate per rs1834481 allele was null (odds ratio, 0.99; 95% confidence interval, 0.94-1.05) when data from the 12 OCAC studies were combined. The effect estimate remained unchanged with the addition of the initial North Carolina Ovarian Cancer Study data. This analysis shows the importance of consortia, like the OCAC, in either confirming or refuting the validity of putative findings in studies with smaller sample sizes. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3567–72)
    Type of Medium: Online Resource
    ISSN: 1055-9965 , 1538-7755
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2008
    detail.hit.zdb_id: 2036781-8
    detail.hit.zdb_id: 1153420-5
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  • 10
    In: Journal of Ecology, Wiley, Vol. 105, No. 5 ( 2017-09), p. 1386-1398
    Abstract: In forests of eastern North America, white‐tailed deer ( O docoileus virginianus ) can directly affect, via herbivory, the presence, abundance and reproductive success of many plant species. In addition, deer indirectly influence understorey communities by altering environmental conditions. To examine how deer indirectly influence understorey plants via environmental modification, we sampled vegetation and environmental variables in‐ and outside deer exclosures (10–20 years old) located in temperate forests in northern Wisconsin and the Upper Peninsula of Michigan, USA . We assessed how excluding deer affected understorey community composition and structure, the soil and light environment, and relationships between direct and indirect effects, using non‐metric multidimensional scaling ( NMDS ), mixed linear models and nonparametric multiplicative regression ( NPMR ). Excluding deer altered sapling communities and several aspects of the understorey environment. Excluding deer from plots with lower overstory basal area increased sapling abundance, decreasing the amount of light available to groundlayer plants. Exclusion also reduced soil compaction and the thickness of the soil E horizon. The composition of understorey communities covaried in apparent response to the environmental factors affected by exclusion. In several common species and groups, E horizon thickness, compaction, openness, and/or total (sapling and overstory) basal area were significant predictors of plant frequency. Complementary analyses revealed that deer exclusion also altered the frequency distributions of several species and groups across environmental space. Synthesis . Deer alter many facets of the understorey environment, such as light availability, soil compaction and thickness of the soil E horizon, which, in turn, appear to mediate variation in plant communities. Those environmental modifications likely compound direct impacts of herbivory as drivers of understorey community change. Our results provide evidence that deer effects on the environment have important implications for forest composition. Thus, we suggest a re‐examination of the common assumption that understorey community shifts stem primarily from tissue removal.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
    SSG: 12
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