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Crowther MS, Rus AI, Mella VSA, Krockenberger MB, Lindsay J, Moore BD, McArthur C. Patch quality and habitat fragmentation shape the foraging patterns of a specialist folivore. Behav Ecol 2022; 33:1007-1017. [DOI: 10.1093/beheco/arac068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 06/17/2022] [Accepted: 06/28/2022] [Indexed: 11/14/2022] Open
Abstract
Abstract
Research on use of foraging patches has focused on why herbivores visit or quit patches, yet little is known about visits to patches over time. Food quality, as reflected by higher nutritional quality and lower plant defenses, and physical patch characteristics, which offer protection from predators and weather, affect patch use and hence should influence their revisitation. Due to the potentially high costs of moving between patches, fragmented habitats are predicted to complicate foraging decisions of many animals. We aimed to determine how food quality, shelter availability and habitat fragmentation influence tree reuse by a specialist folivore, the koala, in a fragmented agricultural landscape. We GPS-tracked 23 koalas in northern New South Wales, Australia and collated number of revisits, average residence time, and average time-to-return to each tree. We measured tree characteristics including food quality (foliar nitrogen and toxic formylated phloroglucinol compounds, FPCs concentrations), tree size, and tree connectedness. We also modeled the costs of locomotion between trees. Koalas re-visited isolated trees with high leaf nitrogen disproportionately often. They spent longer time in trees with high leaf nitrogen, and in large trees used for shelter. They took longer to return to trees with low leaf nitrogen. Tree connectivity reduced travel costs between patches, being either individual or groups of trees. FPC levels had no detectable effect on patch revisitation. We conclude that food quality and shelter drive koala tree re-visits. Scattered, isolated trees with nutrient-rich leaves are valuable resource patches for koalas despite movement costs to reach them.
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Affiliation(s)
- Mathew S Crowther
- School of Life and Environmental Sciences, University of Sydney , Sydney, New South Wales 2006 , Australia
| | - Adrian I Rus
- School of Life and Environmental Sciences, University of Sydney , Sydney, New South Wales 2006 , Australia
| | - Valentina S A Mella
- School of Life and Environmental Sciences, University of Sydney , Sydney, New South Wales 2006 , Australia
- Sydney School of Veterinary Science, University of Sydney , Sydney, New South Wales 2006 , Australia
| | - Mark B Krockenberger
- Sydney School of Veterinary Science, University of Sydney , Sydney, New South Wales 2006 , Australia
- The Westmead Institute for Medical Research , 176 Hawkesbury Road, Westmead, New South Wales 2145 , Australia
- Marie Bashir Institute for Emerging Infectious diseases and Biosecurity, University of Sydney , 176 Hawkesbury Road, Westmead, New South Wales 2145 , Australia
| | - Jasmine Lindsay
- School of Life and Environmental Sciences, University of Sydney , Sydney, New South Wales 2006 , Australia
| | - Ben D Moore
- Hawkesbury Institute for the Environment, Western Sydney University , Richmond, New South Wales 2753 , Australia
| | - Clare McArthur
- School of Life and Environmental Sciences, University of Sydney , Sydney, New South Wales 2006 , Australia
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Borzak CL, Potts BM, Barry KM, Pinkard EA, O'Reilly-Wapstra JM. Genetic stability of physiological responses to defoliation in a eucalypt and altered chemical defence in regrowth foliage. TREE PHYSIOLOGY 2017; 37:220-235. [PMID: 27881800 DOI: 10.1093/treephys/tpw101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 10/20/2016] [Indexed: 06/06/2023]
Abstract
Defoliation may initiate physiological recovery and chemical defence mechanisms that allow a plant to improve fitness after damage. Such responses may result in changes in plant resource allocation that influence growth and foliar chemistry. In this study, we investigated the nature and stability of the defoliation response of juvenile plants from three divergent populations of Eucalyptus globulus Labill. A partial defoliation treatment that removed all upper crown leaves and the apical buds was applied to plants sourced from eight families from each of three populations representing contrasting chemical resistance to mammalian herbivory. Growth, photosynthetic rate and chlorophyll content were assessed pre-defoliation and periodically up to 12 weeks post-defoliation. The content of key plant primary and secondary metabolites was assessed pre-defoliation, at 12 weeks post-defoliation in the old foliage (positioned below the point of defoliation) and in the new foliage of the control plants and regrowth (from axillary buds) on the defoliated plants. There were clear treatment impacts on physiological responses, growth and foliar chemical traits, but despite significant constitutive differences in physiology, growth and chemistry the three E. globulus populations did not vary in their response to foliage loss. Distinct physiological responses to defoliation were observed with treatment plants showing significant up-regulation of photosynthetic rate and increased chlorophyll content in the old foliage remaining in the lower crown. There was a significant increase in the concentrations of a number of foliar chemical compounds in the regrowth arising from previously dormant axillary buds compared with new growth derived from apical meristems. There were changes in biomass allocation; defoliated plants had increased branching and leaf biomass, with changes in regrowth morphology to increase light capture. This study argues for multiple responses of E. globulus juveniles to defoliation involving apical bud loss, including elevated chemical defences matched with increased growth. From a chemical defence perspective, these responses create an enhanced chemical mosaic to the herbivore, with leaves remaining after partial browsing potentially being more palatable than the regrowth. This study demonstrates the multiple independent strategies plants may use to respond to partial defoliation and emphasizes the dynamic interplay between growth and defence in the recovery response.
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Affiliation(s)
- Christina L Borzak
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia
| | - Brad M Potts
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia
| | - Karen M Barry
- School of Land and Food, University of Tasmania, Private Bag 78, Hobart, TAS 7001, Australia
| | - Elizabeth A Pinkard
- CSIRO Ecosystem Sciences and Climate Adaptation Flagship, Private Bag 12, Hobart, TAS7001, Australia
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Phylogeny Explains Variation in The Root Chemistry of Eucalyptus Species. J Chem Ecol 2016; 42:1086-1097. [DOI: 10.1007/s10886-016-0750-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 06/28/2016] [Accepted: 06/30/2016] [Indexed: 12/29/2022]
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Stutz RS, Croak BM, Proschogo N, Banks PB, McArthur C. Olfactory and visual plant cues as drivers of selective herbivory. OIKOS 2016. [DOI: 10.1111/oik.03422] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Rebecca S. Stutz
- School of Life and Environmental Sciences; Univ. of Sydney; Camperdown New South Wales 2006 Australia
- Dept of Zoology; Stockholm Univ.; SE-106 91 Stockholm Sweden
| | - Benjamin M. Croak
- School of Life and Environmental Sciences; Univ. of Sydney; Camperdown New South Wales 2006 Australia
| | - Nicholas Proschogo
- School of Chemistry; Univ. of Sydney; Camperdown New South Wales Australia
| | - Peter B. Banks
- School of Life and Environmental Sciences; Univ. of Sydney; Camperdown New South Wales 2006 Australia
| | - Clare McArthur
- School of Life and Environmental Sciences; Univ. of Sydney; Camperdown New South Wales 2006 Australia
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Huang Y, Wang L, Wang D, Zeng DH, Liu C. How does the foraging behavior of large herbivores cause different associational plant defenses? Sci Rep 2016; 6:20561. [PMID: 26847834 PMCID: PMC4742796 DOI: 10.1038/srep20561] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 01/06/2016] [Indexed: 11/09/2022] Open
Abstract
The attractant-decoy hypothesis predicts that focal plants can defend against herbivory by neighboring with preferred plant species when herbivores make decisions at the plant species scale. The repellent-plant hypothesis assumes that focal plants will gain protection by associating with nonpreferred neighbors when herbivores are selective at the patch scale. However, herbivores usually make foraging decisions at these scales simultaneously. The net outcomes of the focal plant vulnerability could depend on the spatial scale at which the magnitude of selectivity by the herbivores is stronger. We quantified and compared the within- and between-patch overall selectivity index (OSI) of sheep to examine the relationships between associational plant effects and herbivore foraging selectivity. We found that the sheep OSI was stronger at the within- than the between-patch scale, but focal plant vulnerability followed both hypotheses. Focal plants defended herbivory with preferred neighbors when the OSI difference between the two scales was large. Focal plants gained protection with nonpreferred neighbors when the OSI difference was narrowed. Therefore, the difference in selectivity by the herbivores between the relevant scales results in different associational plant defenses. Our study suggests important implications for understanding plant-herbivore interactions and grassland management.
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Affiliation(s)
- Yue Huang
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, 5268 Renmin St., Changchun 130024, P.R. China.,State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P.R. China
| | - Ling Wang
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, 5268 Renmin St., Changchun 130024, P.R. China
| | - Deli Wang
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, 5268 Renmin St., Changchun 130024, P.R. China
| | - De-Hui Zeng
- State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P.R. China
| | - Chen Liu
- Northwest Polytechnical University, Centre for Ecological and Environmental Sciences, Xi'an, 710072, P.R. China
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Borzak CL, Potts BM, Davies NW, O'Reilly-Wapstra JM. Population divergence in the ontogenetic trajectories of foliar terpenes of a Eucalyptus species. ANNALS OF BOTANY 2015; 115:159-170. [PMID: 25434028 PMCID: PMC4284115 DOI: 10.1093/aob/mcu222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 08/27/2014] [Accepted: 09/26/2014] [Indexed: 06/02/2023]
Abstract
BACKGROUND AND AIMS The development of plant secondary metabolites during early life stages can have significant ecological and evolutionary implications for plant-herbivore interactions. Foliar terpenes influence a broad range of ecological interactions, including plant defence, and their expression may be influenced by ontogenetic and genetic factors. This study investigates the role of these factors in the expression of foliar terpene compounds in Eucalyptus globulus seedlings. METHODS Seedlings were sourced from ten families each from three genetically distinct populations, representing relatively high and low chemical resistance to mammalian herbivory. Cotyledon-stage seedlings and consecutive leaf pairs of true leaves were harvested separately across an 8-month period, and analysed for eight monoterpene compounds and six sesquiterpene compounds. KEY RESULTS Foliar terpenes showed a series of dynamic changes with ontogenetic trajectories differing between populations and families, as well as between and within the two major terpene classes. Sesquiterpenes changed rapidly through ontogeny and expressed opposing trajectories between compounds, but showed consistency in pattern between populations. Conversely, changed expression in monoterpene trajectories was population- and compound-specific. CONCLUSIONS The results suggest that adaptive opportunities exist for changing levels of terpene content through ontogeny, and evolution may exploit the ontogenetic patterns of change in these compounds to create a diverse ontogenetic chemical mosaic with which to defend the plant. It is hypothesized that the observed genetically based patterns in terpene ontogenetic trajectories reflect multiple changes in the regulation of genes throughout different terpene biosynthetic pathways.
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Affiliation(s)
- Christina L Borzak
- School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia
| | - Brad M Potts
- School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia
| | - Noel W Davies
- School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia
| | - Julianne M O'Reilly-Wapstra
- School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia
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Quantifying the response of free-ranging mammalian herbivores to the interplay between plant defense and nutrient concentrations. Oecologia 2014; 175:1167-77. [DOI: 10.1007/s00442-014-2980-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 05/22/2014] [Indexed: 11/27/2022]
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Häggman H, Raybould A, Borem A, Fox T, Handley L, Hertzberg M, Lu MZ, Macdonald P, Oguchi T, Pasquali G, Pearson L, Peter G, Quemada H, Séguin A, Tattersall K, Ulian E, Walter C, McLean M. Genetically engineered trees for plantation forests: key considerations for environmental risk assessment. PLANT BIOTECHNOLOGY JOURNAL 2013; 11:785-98. [PMID: 23915092 PMCID: PMC3823068 DOI: 10.1111/pbi.12100] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 06/18/2013] [Accepted: 06/23/2013] [Indexed: 05/18/2023]
Abstract
Forests are vital to the world's ecological, social, cultural and economic well-being yet sustainable provision of goods and services from forests is increasingly challenged by pressures such as growing demand for wood and other forest products, land conversion and degradation, and climate change. Intensively managed, highly productive forestry incorporating the most advanced methods for tree breeding, including the application of genetic engineering (GE), has tremendous potential for producing more wood on less land. However, the deployment of GE trees in plantation forests is a controversial topic and concerns have been particularly expressed about potential harms to the environment. This paper, prepared by an international group of experts in silviculture, forest tree breeding, forest biotechnology and environmental risk assessment (ERA) that met in April 2012, examines how the ERA paradigm used for GE crop plants may be applied to GE trees for use in plantation forests. It emphasizes the importance of differentiating between ERA for confined field trials of GE trees, and ERA for unconfined or commercial-scale releases. In the case of the latter, particular attention is paid to characteristics of forest trees that distinguish them from shorter-lived plant species, the temporal and spatial scale of forests, and the biodiversity of the plantation forest as a receiving environment.
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Affiliation(s)
- Hely Häggman
- Department of Biology, University of OuluOulu, Finland
| | - Alan Raybould
- Syngenta Jealott's Hill International Research CentreBracknell, UK
| | - Aluizio Borem
- Departamento de Fitotecnia, Universidade Federal de ViçosaViçosa, Brazil
| | - Thomas Fox
- Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State UniversityBlacksburg, VA, USA
| | - Levis Handley
- Biotechnology Regulatory Services, United States Department of AgricultureRiverdale, MD, USA
| | | | - Meng-Zu Lu
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of ForestryBeijing, China
| | - Philip Macdonald
- Plant and Biotechnology Risk Assessment, Canadian Food Inspection AgencyOttawa, ON, Canada
| | - Taichi Oguchi
- Gene Research Center, University of TsukubaTsukuba, Japan
| | - Giancarlo Pasquali
- Centro de Biotecnologia, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil
| | | | - Gary Peter
- School of Forest Resources and Conservation, University of FloridaGainesville, FL, USA
| | | | | | | | | | | | - Morven McLean
- Center for Environmental Risk AssessmentWashington, DC, USA
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Chemical variation in a dominant tree species: population divergence, selection and genetic stability across environments. PLoS One 2013; 8:e58416. [PMID: 23526981 PMCID: PMC3603948 DOI: 10.1371/journal.pone.0058416] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 02/04/2013] [Indexed: 11/27/2022] Open
Abstract
Understanding among and within population genetic variation of ecologically important plant traits provides insight into the potential evolutionary processes affecting those traits. The strength and consistency of selection driving variability in traits would be affected by plasticity in differences among genotypes across environments (G×E). We investigated population divergence, selection and environmental plasticity of foliar plant secondary metabolites (PSMs) in a dominant tree species, Eucalyptus globulus. Using two common garden trials we examined variation in PSMs at multiple genetic scales; among 12 populations covering the full geographic range of the species and among up to 60 families within populations. Significant genetic variation in the expression of many PSMs resides both among and within populations of E. globulus with moderate (e.g., sideroxylonal A h2op = 0.24) to high (e.g., macrocarpal G h2op = 0.48) narrow sense heritabilities and high coefficients of additive genetic variation estimated for some compounds. A comparison of Qst and Fst estimates suggest that variability in some of these traits may be due to selection. Importantly, there was no genetic by environment interaction in the expression of any of the quantitative chemical traits despite often significant site effects. These results provide evidence that natural selection has contributed to population divergence in PSMs in E. globulus, and identifies the formylated phloroglucinol compounds (particularly sideroxylonal) and a dominant oil, 1,8-cineole, as candidates for traits whose genetic architecture has been shaped by divergent selection. Additionally, as the genetic differences in these PSMs that influence community phenotypes is stable across environments, the role of plant genotype in structuring communities is strengthened and these genotypic differences may be relatively stable under global environmental changes.
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Mooney EH, Niesenbaum RA. Population-specific responses to light influence herbivory in the understory shrubLindera benzoin. Ecology 2012; 93:2683-92. [PMID: 23431598 DOI: 10.1890/11-1620.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- E H Mooney
- Massachusetts College of Liberal Arts, 375 Church Street, North Adams, Massachusetts 01247, USA.
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11
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Nersesian CL, Banks PB, McArthur C. Influences of Plant Toxins and Their Spatial Distribution on Foraging by the Common Brushtail Possum, a Generalist Mammalian Herbivore. J Chem Ecol 2012. [DOI: 10.1007/s10886-012-0218-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Kimball BA, Russell JH, Ott PK. Phytochemical variation within a single plant species influences foraging behavior of deer. OIKOS 2011. [DOI: 10.1111/j.1600-0706.2011.19515.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Pinkard EA, Battaglia M, Roxburgh S, O'Grady AP. Estimating forest net primary production under changing climate: adding pests into the equation. TREE PHYSIOLOGY 2011; 31:686-699. [PMID: 21746746 DOI: 10.1093/treephys/tpr054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The current approach to modelling pest impacts on forest net primary production (NPP) is to apply a constant modifier. This does not capture the large spatial and temporal variability in pest abundance and activity that can occur, meaning that overestimates or underestimates of pest impacts on forest NPP are likely. Taking a more mechanistic approach that incorporates an understanding of how physiology is influenced by pest attack, enables us to better capture system feedbacks and dynamics, thereby improving the capacity to predict into novel situations such as changing climate, and to account for both changes in pest activity and host responses to the growing environment now and into the future. We reviewed the effects of pests on forest NPP and found a range of responses and physiological mechanisms underlying those responses. Pest outbreaks can clearly be a major perturbation to forest NPP, and it seems likely that the frequency and intensity of pest outbreaks, and the ways in which host species respond to pest damage, will change in the future. We summarized these impacts in the form of a conceptual model at leaf, tree and stand scales, and compared the physiological processes embedded within that framework with the capacity of a representative range of NPP models to capture those processes. We found that some models can encapsulate some of the processes, but no model can comprehensively account for the range of physiological responses to pest attack experienced by trees. This is not surprising, given the paucity of empirical data for most of the world's forests, and that the models were developed primarily for other purposes. We conclude with a list of the key physiological processes and pathways that need to be included in forest growth models in order to adequately capture pest impacts on forest NPP under current and future climate scenarios, the equations that might enable this and the empirical data required to support them.
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Affiliation(s)
- E A Pinkard
- CSIRO Ecosystem Science, Climate Adaptation Flagship and Sustainable Agriculture Flagship, Private Bag 12, Hobart 7001, Australia.
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14
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Nersesian CL, Banks PB, McArthur C. Titrating the cost of plant toxins against predators: determining the tipping point for foraging herbivores. J Anim Ecol 2011; 80:753-60. [PMID: 21366564 DOI: 10.1111/j.1365-2656.2011.01822.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. Foraging herbivores must deal with plant characteristics that inhibit feeding and they must avoid being eaten. Principally, toxins limit food intake, while predation risk alters how long animals are prepared to harvest resources. Each of these factors strongly affects how herbivores use food patches, and both constraints can pose immediate proximate costs and long-term consequences to fitness. 2. Using a generalist mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), our aim was to quantitatively compare the influence of plant toxin and predation risk on foraging decisions. 3. We performed a titration experiment by offering animals a choice between non-toxic food at a risky patch paired with food with one of five toxin concentrations at a safe patch. This allowed us to identify the tipping point, where the cost of toxin in the safe food patch was equivalent to the perceived predation risk in the alternative patch. 4. At low toxin concentration, animals ate more from the safe than the risky patch. As toxin concentration increased at the safe patch, intake shifted until animals ate mainly from the risky patch. This shift was associated with behavioural changes: animals spent more time and fed longer at the risky patch, while vigilance increased at both risky and safe patches. 5. Our results demonstrate that the variation in toxin concentration, which occurs intraspecifically among plants, can critically influence the relative cost of predation risk on foraging. We show that herbivores quantify, compare and balance these two different but proximate costs, altering their foraging patterns in the process. This has potential ecological and evolutionary implications for the production of plant defence compounds in relation to spatial variation in predation risk to herbivores.
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Affiliation(s)
- Carolyn L Nersesian
- School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia.
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15
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Andrew RL, Wallis IR, Harwood CE, Foley WJ. Genetic and environmental contributions to variation and population divergence in a broad-spectrum foliar defence of Eucalyptus tricarpa. ANNALS OF BOTANY 2010; 105:707-17. [PMID: 20228089 PMCID: PMC2859910 DOI: 10.1093/aob/mcq034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
BACKGROUND AND AIMS Both environmental and genetic effects contribute to phenotypic variation within and among populations. Genetic differentiation of quantitative traits among populations has been shown in many species, yet it can also be accompanied by other genetic changes, such as divergence in phenotypic plasticity and in genetic variance. Sideroxylonal (a formylated phloroglucinol compound or FPC) is an important chemical defence in eucalypts. The effect of environmental variation on its production is a critical gap in our understanding of its genetics and evolution. METHODS The stability of genetic variation in sideroxylonal was assessed within and among populations of Eucalyptus tricarpa in three replicated provenance/progeny trials. The covariance structure of the data was also modelled to test whether genetic variances were consistent among populations and Fain's test was applied for major gene effects. KEY RESULTS A significant genotype x environment interaction occurred at the level of population, and was related to temperature range and seasonality in source populations. Within-population genetic variation was not affected by genotype x environment effects or different sampling years. However, within-population genetic variance for sideroxylonal concentration differed significantly among source populations. Regression of family variance on family mean suggested that this trait is subject to major gene effects, which could explain the observed differences in genetic variances among populations. CONCLUSIONS These results highlight the importance of replicated common-garden experiments for understanding the genetic basis of population differences. Genotype x environment interactions are unlikely to impede evolution or responses to artificial selection on sideroxylonal, but the lack of genetic variation in some populations may be a constraint. The results are broadly consistent with localized selection on foliar defence and illustrate that differentiation in population means, whether due to selection or to drift, can be accompanied by changes in other characteristics, such as plasticity and genetic variance.
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Affiliation(s)
- Rose L Andrew
- School of Botany and Zoology, The Australian National University, Canberra, ACT 0200, Australia.
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MCARTHUR CLARE, LONEY PRUEE, DAVIES NOELW, JORDAN GREGORYJ. Early ontogenetic trajectories vary among defence chemicals in seedlings of a fast-growing eucalypt. AUSTRAL ECOL 2010. [DOI: 10.1111/j.1442-9993.2009.02021.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Native plant/herbivore interactions as determinants of the ecological and evolutionary effects of invasive mammalian herbivores: the case of the common brushtail possum. Biol Invasions 2009. [DOI: 10.1007/s10530-009-9629-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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18
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Miller AM, McArthur C, Smethurst PJ. Spatial scale and opportunities for choice influence browsing and associational refuges of focal plants. J Anim Ecol 2009; 78:1134-42. [PMID: 19594661 DOI: 10.1111/j.1365-2656.2009.01589.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Foraging decisions by herbivores depend on variation in food types, the scale(s) at which this variation occurs and the opportunity and capacity for herbivores to respond to such variation. These decisions affect not only the herbivores themselves, but also the vulnerability of individual plants to being eaten. Associational plant refuges, in which neighbouring plants alter focal plant vulnerability, are an emergent property of foraging decisions. 2. Using the red-bellied pademelon (Thylogale billardierii) as a model generalist mammalian herbivore, we investigated the spatial scale(s) at which animals made foraging decisions and the resultant effect on focal plant vulnerability. In a replicated design, we varied vegetation at the individual plant scale, generating intraspecific differences in Eucalyptus nitens seedlings by altering their nutrient status (high, low). We varied vegetation at the patch scale, in which seedlings were planted, using high- (grass) and low- (herbicided) quality patches. Animals were allowed to choose where they fed and what they ate. Animal behaviour was recorded and intake of seedlings measured. 3. We found that animals made foraging decisions first at the patch scale then at the scale of individual plants; both patch and focal seedling characteristics influenced browsing. Pademelons spent most of their time in high-quality patches, and seedlings were consequently more vulnerable there than in low-quality patches. Pademelons also ate more foliage from high- than from low-nutrient status seedlings. This behaviour concentrated resources, increasing foraging efficiency and making focal plants more vulnerable to browsing. 4. The opportunity and capacity to choose at both plant and patch scales resulted in a pattern of focal plant vulnerability consistent with the repellent-plant hypothesis. This contrasts with our previous study, in which animals were only provided with choice at the plant level and plant vulnerability followed the attractant-decoy hypothesis. These combined results demonstrate that the influence of neighbouring vegetation on consumption of a focal plant depends on the spatial scale of selection and on opportunities (and capacity) for herbivores to choose.
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Freeman JS, O'Reilly-Wapstra JM, Vaillancourt RE, Wiggins N, Potts BM. Quantitative trait loci for key defensive compounds affecting herbivory of eucalypts in Australia. THE NEW PHYTOLOGIST 2008; 178:846-851. [PMID: 18373517 DOI: 10.1111/j.1469-8137.2008.02417.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
* Formylated phloroglucinols (FPCs) are key defensive compounds that influence herbivory by mammals and arthropods in eucalypts. However, the genetic architecture underlying variation in their levels remains poorly understood. * Quantitative trait loci (QTL) analysis for the concentrations of two major FPCs, sideroxylonal A and macrocarpal G, was conducted using juvenile leaves from 112 clonally duplicated progenies from an outcross F2 of Eucalyptus globulus. * Two unlinked QTL were located for macrocarpal, while another unlinked QTL was located for sideroxylonal. The sideroxylonal QTL collocated with one for total sideroxylonal previously reported using adult Eucalyptus nitens foliage, providing independent validation in a different evolutionary lineage and a different ontogenetic stage. * Given the potential widespread occurrence of these QTL, their ontogenetic stability, and their impact on a range of dependent herbivores, it is possible that they have extended phenotypic effects in the Australian forest landscape.
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Affiliation(s)
- J S Freeman
- School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, Australia 7001
| | - J M O'Reilly-Wapstra
- School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, Australia 7001
| | - R E Vaillancourt
- School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, Australia 7001
| | - N Wiggins
- School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, Australia 7001
| | - B M Potts
- School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, Australia 7001
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O'Reilly-Wapstra JM, Humphreys JR, Potts BM. Stability of genetic-based defensive chemistry across life stages in a Eucalyptus species. J Chem Ecol 2007; 33:1876-84. [PMID: 17924167 DOI: 10.1007/s10886-007-9366-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 09/10/2007] [Indexed: 11/26/2022]
Abstract
Defensive chemistry is a key plant fitness trait, and the investigation of the expression of plant secondary metabolites across life stages is important in understanding the lifetime evolutionary selection pressures on a plant. The expression of genetic-based differences in foliar defensive chemistry, known to influence mammalian herbivore preferences, was studied across two contrasting life phases of the heteroblastic tree, Eucalyptus globulus. With plants from different subraces of E. globulus growing in a field trial, we compared the levels of seven chemical constituents in adult and juvenile foliage from related coppiced plants. Defensive chemistry was generally higher in more vulnerable coppice foliage than adult foliage. Significant, genetic-based differences among subraces were detected for two key defensive chemicals, a sideroxylonal and a macrocarpal, and these differences were stable across life phases. In contrast, significant differences among subraces in adult leaf condensed tannins were not evident in the coppice because of the absence of this group of tannins in this foliage. These findings lend support to hypotheses that suggest condensed tannins may have evolved for reasons other than mammalian herbivore defense.
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Affiliation(s)
- Julianne M O'Reilly-Wapstra
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia.
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Wise MJ. Evolutionary ecology of resistance to herbivory: an investigation of potential genetic constraints in the multiple-herbivore community of Solanum carolinense. THE NEW PHYTOLOGIST 2007; 175:773-784. [PMID: 17688592 DOI: 10.1111/j.1469-8137.2007.02143.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
As part of a study of the ecological and evolutionary dynamics of herbivore resistance in Solanum carolinense (horsenettle), potential genetic constraints to the evolution of resistance to 11 of its most common herbivores were investigated. Leaf, flower, fruit, and stem herbivory were measured in a field experiment involving 24 ramets of each of 40 horsenettle genets. The experimental plant population contained significant genetic variation for resistance to all 11 species of herbivore. For only one species was there an indication of a genotype-by-environment interaction in the expression of resistance that might constrain its evolution. Genetic correlations in resistance to different species were common but not universal, with seven negative and 12 positive correlations out of the 55 pairwise species comparisons. Correlations were independent of plant part fed upon. The evolution of the resistance of horsenettle to most of its diverse community of herbivores does not appear to be prevented by a lack of genetic variation or by genotype-by-environment interactions in resistance. Negative genetic correlations in resistance to different herbivores may play a small role in slowing the evolution of resistance, but positive correlations may play at least as large a role in facilitating its evolution.
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Affiliation(s)
- Michael J Wise
- Department of Biology, Box 90338 Duke University, Durham, NC 27708, USA; Present address: Department of Biology, Bucknell University, Lewisburg, PA 17837, USA
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LONEY PE, McARTHUR C, POTTS BM, JORDAN GJ. How does ontogeny in a Eucalyptus species affect patterns of herbivory by Brushtail Possums? Funct Ecol 2006. [DOI: 10.1111/j.1365-2435.2006.01193.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Loney PE, McArthur C, Sanson GD, Davies NW, Close DC, Jordan GJ. How do soil nutrients affect within-plant patterns of herbivory in seedlings of Eucalyptus nitens? Oecologia 2006; 150:409-20. [PMID: 17031701 DOI: 10.1007/s00442-006-0525-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Accepted: 07/27/2006] [Indexed: 10/24/2022]
Abstract
This study assessed how the palatability of leaves of different age classes (young, intermediate and older) of Eucalyptus nitens seedlings varied with plant nutrient status, based on captive feeding trials with two mammalian herbivores, red-bellied pademelons (Thylogale billardierii), and common brushtail possums (Trichosurus vulpecula). Seedlings were grown under three nutrient treatments (low, medium and high), and we determined how palatability was related to chemical and physical characteristics of the leaves. Pademelons ate more older leaves than young and intermediate leaves for all treatments. This pattern was best explained by sideroxylonals (formylated phloroglucinol compounds known to deter herbivory by other marsupials), and/or essential oil compounds that were present in lower concentrations in older leaves. In the low-nutrient treatment, possums also ate more of the older leaves. However, in the medium- and high-nutrient treatments, possums ate more intermediate leaves than older leaves and showed a behavioural preference for young leaves (consuming younger leaves first) over intermediate and older leaves, in spite of high levels of sideroxylonals and essential oils. The young leaves did, however, have the highest nitrogen concentration of all the leaf age classes. Thus, either sideroxylonals and essential oils provided little or no deterrent to possums, or the deterrent was outweighed by other factors such as high nitrogen. This study indicates that mammalian herbivores show different levels of relative use and damage to leaf age classes at varying levels of plant nutrient status and, therefore, their impact on plant fitness may vary with environment.
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Affiliation(s)
- Prue E Loney
- Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 12, Hobart, TAS, 7001, Australia
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