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Freedman MG, Long RW, Ramírez SR, Strauss SY. Evidence for Reductions in Physical and Chemical Plant Defense Traits in Island Flora. PLANTS (BASEL, SWITZERLAND) 2024; 13:1026. [PMID: 38611555 PMCID: PMC11013342 DOI: 10.3390/plants13071026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Revised: 03/28/2024] [Accepted: 03/29/2024] [Indexed: 04/14/2024]
Abstract
Reduced defense against large herbivores has been suggested to be part of the "island syndrome" in plants. However, empirical evidence for this pattern is mixed. In this paper, we present two studies that compare putative physical and chemical defense traits from plants on the California Channel Islands and nearby mainland based on sampling of both field and common garden plants. In the first study, we focus on five pairs of woody shrubs from three island and three mainland locations and find evidence for increased leaf area, decreased marginal leaf spines, and decreased concentrations of cyanogenic glycosides in island plants. We observed similar increases in leaf area and decreases in defense traits when comparing island and mainland genotypes grown together in botanic gardens, suggesting that trait differences are not solely driven by abiotic differences between island and mainland sites. In the second study, we conducted a common garden experiment with a perennial herb-Stachys bullata (Lamiaceae)-collected from two island and four mainland locations. Compared to their mainland relatives, island genotypes show highly reduced glandular trichomes and a nearly 100-fold reduction in mono- and sesquiterpene compounds from leaf surfaces. Island genotypes also had significantly higher specific leaf area, somewhat lower rates of gas exchange, and greater aboveground biomass than mainland genotypes across two years of study, potentially reflecting a broader shift in growth habit. Together, our results provide evidence for reduced expression of putative defense traits in island plants, though these results may reflect adaptation to both biotic (i.e., the historical absence of large herbivores) and climatic conditions on islands.
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Affiliation(s)
- Micah G. Freedman
- Center for Population Biology, University of California, Davis, CA 95616, USA
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Randall W. Long
- Department of Biology, Lewis & Clark College, Portland, OR 97219, USA
| | - Santiago R. Ramírez
- Center for Population Biology, University of California, Davis, CA 95616, USA
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Sharon Y. Strauss
- Center for Population Biology, University of California, Davis, CA 95616, USA
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
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John A, Olden JD, Oldfather MF, Kling MM, Ackerly DD. Topography influences diurnal and seasonal microclimate fluctuations in hilly terrain environments of coastal California. PLoS One 2024; 19:e0300378. [PMID: 38551923 PMCID: PMC10980203 DOI: 10.1371/journal.pone.0300378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 02/26/2024] [Indexed: 04/01/2024] Open
Abstract
Understanding the topographic basis for microclimatic variation remains fundamental to predicting the site level effects of warming air temperatures. Quantifying diurnal fluctuation and seasonal extremes in relation to topography offers insight into the potential relationship between site level conditions and changes in regional climate. The present study investigated an annual understory temperature regime for 50 sites distributed across a topographically diverse area (>12 km2) comprised of mixed evergreen-deciduous woodland vegetation typical of California coastal ranges. We investigated the effect of topography and tree cover on site-to-site variation in near-surface temperatures using a combination of multiple linear regression and multivariate techniques. Sites in topographically depressed areas (e.g., valley bottoms) exhibited larger seasonal and diurnal variation. Elevation (at 10 m resolution) was found to be the primary driver of daily and seasonal variations, in addition to hillslope position, canopy cover and northness. The elevation effect on seasonal mean temperatures was inverted, reflecting large-scale cold-air pooling in the study region, with elevated minimum and mean temperature at higher elevations. Additionally, several of our sites showed considerable buffering (dampened diurnal and seasonal temperature fluctuations) compared to average regional conditions measured at an on-site weather station. Results from this study help inform efforts to extrapolate temperature records across large landscapes and have the potential to improve our ecological understanding of fine-scale seasonal climate variation in coastal range environments.
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Affiliation(s)
- Aji John
- Department of Biology, University of Washington, Seattle, WA, United States of America
| | - Julian D. Olden
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, United States of America
| | - Meagan F. Oldfather
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, United States of America
| | - Matthew M. Kling
- Department of Integrative Biology, University of California–Berkeley, Berkeley, CA, United States of America
| | - David D. Ackerly
- Department of Integrative Biology, University of California–Berkeley, Berkeley, CA, United States of America
- Department of Environmental Science, Policy and Management, University of California–Berkeley, Berkeley, CA, United States of America
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Keppel G, Sarnow U, Biffin E, Peters S, Fitzgerald D, Boutsalis E, Waycott M, Guerin GR. Population decline in a Pleistocene refugium: Stepwise, drought-related dieback of a South Australian eucalypt. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 876:162697. [PMID: 36898535 DOI: 10.1016/j.scitotenv.2023.162697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 03/03/2023] [Accepted: 03/03/2023] [Indexed: 06/18/2023]
Abstract
Refugia can facilitate the persistence of species under long-term environmental change, but it is not clear if Pleistocene refugia will remain functional as anthropogenic climate change progresses. Dieback in populations restricted to refugia therefore raises concerns about their long-term persistence. Using repeat field surveys, we investigate dieback in an isolated population of Eucalyptus macrorhyncha during two droughts and discuss prospects for its continued persistence in a Pleistocene refugium. We first confirm that the Clare Valley in South Australia has constituted a long-term refugium for the species, with the population being genetically highly distinct from other conspecific populations. However, the population lost >40 % of individuals and biomass through the droughts, with mortality being just below 20 % after the Millennium Drought (2000-2009) and almost 25 % after the Big Dry (2017-2019). The best predictors of mortality differed after each drought. While north-facing aspect of a sampling location was significant positive predictor after both droughts, biomass density and slope were significant negative predictors only after the Millennium Drought, and distance to the north-west corner of the population, which intercepts hot, dry winds, was a significant positive predictor after the Big Dry only. This suggests that more marginal sites with low biomass and sites located on flat plateaus were more vulnerable initially, but that heat-stress was an important driver of dieback during the Big Dry. Therefore, the causative drivers of dieback may change during population decline. Regeneration occurred predominantly on southern and eastern aspects, which would receive the least solar radiation. While this refugial population is experiencing severe decline, some gullies with lower solar radiation appear to support relatively healthy, regenerating stands of red stringybark, providing hope for persistence in small pockets. Monitoring and managing these pockets during future droughts will be essential to ensure the persistence of this isolated and genetically unique population.
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Affiliation(s)
- Gunnar Keppel
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia; AMAP, Université de Montpellier, CIRAD, CNRS, INRAE, IRD, Montpellier, France.
| | - Udo Sarnow
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia
| | - Ed Biffin
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, Australia.
| | - Stefan Peters
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Donna Fitzgerald
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Evan Boutsalis
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Michelle Waycott
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, Australia.
| | - Greg R Guerin
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia.
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Haynes A. When less is more: failure to adapt to local conditions sometimes boosts resilience. CONSERVATION PHYSIOLOGY 2021; 9:coab055. [PMID: 34277010 PMCID: PMC8280940 DOI: 10.1093/conphys/coab055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 06/18/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Alison Haynes
- Centre for Sustainable Ecosystem Solutions, University of Wollongong, New South Wales 2522, Australia
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Venturas MD, Todd HN, Trugman AT, Anderegg WRL. Understanding and predicting forest mortality in the western United States using long-term forest inventory data and modeled hydraulic damage. THE NEW PHYTOLOGIST 2021; 230:1896-1910. [PMID: 33112415 DOI: 10.1111/nph.17043] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 10/20/2020] [Indexed: 06/11/2023]
Abstract
Global warming is expected to exacerbate the duration and intensity of droughts in the western United States, which may lead to increased tree mortality. A prevailing proximal mechanism of drought-induced tree mortality is hydraulic damage, but predicting tree mortality from hydraulic theory and climate data still remains a major scientific challenge. We used forest inventory data and a plant hydraulic model (HM) to address three questions: can we capture regional patterns of drought-induced tree mortality with HM-predicted damage thresholds; do HM metrics improve predictions of mortality across broad spatial areas; and what are the dominant controls of forest mortality when considering stand characteristics, climate metrics, and simulated hydraulic stress? We found that the amount of variance explained by models predicting mortality was limited (R2 median = 0.10, R2 range: 0.00-0.52). HM outputs, including hydraulic damage and carbon assimilation diagnostics, moderately improve mortality prediction across the western US compared with models using stand and climate predictors alone. Among factors considered, metrics of stand density and tree size tended to be some of the most critical factors explaining mortality, probably highlighting the important roles of structural overshoot, stand development, and biotic agent host selection and outbreaks in mortality patterns.
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Affiliation(s)
- Martin D Venturas
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Henry N Todd
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Anna T Trugman
- Department of Geography, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - William R L Anderegg
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
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Skelton RP, Anderegg LDL, Diaz J, Kling MM, Papper P, Lamarque LJ, Delzon S, Dawson TE, Ackerly DD. Evolutionary relationships between drought-related traits and climate shape large hydraulic safety margins in western North American oaks. Proc Natl Acad Sci U S A 2021; 118:e2008987118. [PMID: 33649205 PMCID: PMC7958251 DOI: 10.1073/pnas.2008987118] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Quantitative knowledge of xylem physical tolerance limits to dehydration is essential to understanding plant drought tolerance but is lacking in many long-vessel angiosperms. We examine the hypothesis that a fundamental association between sustained xylem water transport and downstream tissue function should select for xylem that avoids embolism in long-vessel trees by quantifying xylem capacity to withstand air entry of western North American oaks (Quercus spp.). Optical visualization showed that 50% of embolism occurs at water potentials below -2.7 MPa in all 19 species, and -6.6 MPa in the most resistant species. By mapping the evolution of xylem vulnerability to embolism onto a fossil-dated phylogeny of the western North American oaks, we found large differences between clades (sections) while closely related species within each clade vary little in their capacity to withstand air entry. Phylogenetic conservatism in xylem physical tolerance, together with a significant correlation between species distributions along rainfall gradients and their dehydration tolerance, suggests that closely related species occupy similar climatic niches and that species' geographic ranges may have shifted along aridity gradients in accordance with their physical tolerance. Such trends, coupled with evolutionary associations between capacity to withstand xylem embolism and other hydraulic-related traits, yield wide margins of safety against embolism in oaks from diverse habitats. Evolved responses of the vascular system to aridity support the embolism avoidance hypothesis and reveal the importance of quantifying plant capacity to withstand xylem embolism for understanding function and biogeography of some of the Northern Hemisphere's most ecologically and economically important plants.
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Affiliation(s)
- Robert P Skelton
- Department of Integrative Biology, University of California, Berkeley, CA 94720;
- Fynbos Node, South African Environmental Observation Network, Newlands 7735, Cape Town, South Africa
| | - Leander D L Anderegg
- Department of Integrative Biology, University of California, Berkeley, CA 94720
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93117
| | - Jessica Diaz
- Department of Integrative Biology, University of California, Berkeley, CA 94720
| | - Matthew M Kling
- Department of Integrative Biology, University of California, Berkeley, CA 94720
| | - Prahlad Papper
- Department of Integrative Biology, University of California, Berkeley, CA 94720
| | - Laurent J Lamarque
- Département des Sciences de l'Environnement, Université du Québec à Trois-Rivières, Trois-Rivières, QC G9A 5H7, Canada
- Université de Bordeaux, INRAE (Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement), UMR BIOGECO, 33615 Pessac, France
| | - Sylvain Delzon
- Université de Bordeaux, INRAE (Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement), UMR BIOGECO, 33615 Pessac, France
| | - Todd E Dawson
- Department of Integrative Biology, University of California, Berkeley, CA 94720
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720
| | - David D Ackerly
- Department of Integrative Biology, University of California, Berkeley, CA 94720
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720
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