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Rhodes AC, Plowes RM, Bowman EA, Gaitho A, Ng'Iru I, Martins DJ, Gilbert LE. Systematic reduction of natural enemies and competition across variable precipitation approximates buffelgrass invasiveness ( Cenchrus ciliaris) in its native range. Ecol Evol 2024; 14:e11350. [PMID: 38737568 PMCID: PMC11087885 DOI: 10.1002/ece3.11350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/28/2024] [Accepted: 04/12/2024] [Indexed: 05/14/2024] Open
Abstract
Invasive grasses cause devastating losses to biodiversity and ecosystem function directly and indirectly by altering ecosystem processes. Escape from natural enemies, plant-plant competition, and variable resource availability provide frameworks for understanding invasion. However, we lack a clear understanding of how natural stressors interact in their native range to regulate invasiveness. In this study, we reduced diverse guilds of natural enemies and plant competitors of the highly invasive buffelgrass across a precipitation gradient throughout major climatic shifts in Laikipia, Kenya. To do this, we used a long-term ungulate exclosure experiment design across a precipitation gradient with nested treatments that (1) reduced plant competition through clipping, (2) reduced insects through systemic insecticide, and (3) reduced fungal associates through fungicide application. Additionally, we measured the interaction of ungulates on two stem-boring insect species feeding on buffelgrass. Finally, we measured a multiyear smut fungus outbreak. Our findings suggest that buffelgrass exhibits invasive qualities when released from a diverse group of natural stressors in its native range. We show natural enemies interact with precipitation to alter buffelgrass productivity patterns. In addition, interspecific plant competition decreased the basal area of buffelgrass, suggesting that biotic resistance mediates buffelgrass dominance in the home range. Surprisingly, systemic insecticides and fungicides did not impact buffelgrass production or reproduction, perhaps because other guilds filled the niche space in these highly diverse systems. For example, in the absence of ungulates, we showed an increase in host-specific stem-galling insects, where these insects compensated for reduced ungulate use. Finally, we documented a smut outbreak in 2020 and 2021, corresponding to highly variable precipitation patterns caused by a shifting Indian Ocean Dipole. In conclusion, we observed how reducing natural enemies and competitors and certain interactions increased properties related to buffelgrass invasiveness.
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Affiliation(s)
- Aaron C. Rhodes
- Brackenridge Field LaboratoryThe University of Texas at AustinAustinTexasUSA
| | - Robert M. Plowes
- Brackenridge Field LaboratoryThe University of Texas at AustinAustinTexasUSA
| | - Elizabeth A. Bowman
- Brackenridge Field LaboratoryThe University of Texas at AustinAustinTexasUSA
- Hiro Technologies, IncAustinTexasUSA
| | - Aimee Gaitho
- Mpala Research Centre NanyukiNanyukiKenya
- Turkana Basin InstituteNairobiKenya
| | - Ivy Ng'Iru
- UK Centre for Ecology & HydrologyCardiff UniversityWallingfordUK
| | | | - Lawrence E. Gilbert
- Brackenridge Field LaboratoryThe University of Texas at AustinAustinTexasUSA
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2
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Grunberg RL, Halliday FW, Heckman RW, Joyner BN, O’Keeffe KR, Mitchell CE. Disease decreases variation in host community structure in an old-field grassland. PLoS One 2023; 18:e0293495. [PMID: 37889914 PMCID: PMC10610459 DOI: 10.1371/journal.pone.0293495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 10/13/2023] [Indexed: 10/29/2023] Open
Abstract
Disease may drive variation in host community structure by modifying the interplay of deterministic and stochastic processes that shape communities. For instance, deterministic processes like ecological selection can benefit species less impacted by disease. When communities have higher levels of disease and disease consistently selects for certain host species, this can reduce variation in host community composition. On the other hand, when host communities are less impacted by disease and selection is weaker, stochastic processes (e.g., drift, dispersal) may play a bigger role in host community structure, which can increase variation among communities. While effects of disease on host community structure have been quantified in field experiments, few have addressed the role of disease in modulating variation in structure among host communities. To address this, we conducted a field experiment spanning three years, using a tractable system: foliar fungal pathogens in an old-field grassland community dominated by the grass Lolium arundinaceum, tall fescue. We reduced foliar fungal disease burden in replicate host communities (experimental plots in intact vegetation) in three fungicide regimens that varied in the seasonal duration of fungicide treatment and included a fungicide-free control. We measured host diversity, biomass, and variation in community structure among replicate communities. Disease reduction generally decreased plant richness and increased aboveground biomass relative to communities experiencing ambient levels of disease. These changes in richness and aboveground biomass were consistent across years despite changes in structure of the plant communities over the experiment's three years. Importantly, disease reduction amplified host community variation, suggesting that disease diminished the degree to which host communities were structured by stochastic processes. These results of experimental disease reduction both highlight the potential importance of stochastic processes in plant communities and reveal the potential for disease to regulate variation in host community structure.
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Affiliation(s)
- Rita L. Grunberg
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Fletcher W. Halliday
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Robert W. Heckman
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Brooklynn N. Joyner
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Kayleigh R. O’Keeffe
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Charles E. Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, North Carolina, United States of America
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3
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Ma N, Kou L, Li S, Dai X, Meng S, Jiang L, Xue Y, Zheng J, Fu X, Wang H. Plant-soil feedback regulates the trade-off between phosphorus acquisition pathways in Pinus elliottii. TREE PHYSIOLOGY 2023; 43:1092-1103. [PMID: 37074159 PMCID: PMC10785040 DOI: 10.1093/treephys/tpad044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/31/2023] [Accepted: 04/11/2023] [Indexed: 05/03/2023]
Abstract
Plant-soil feedback (PSF) is conventionally characterized by plant biomass growth, yet it remains unclear how PSF affects plant nutrient acquisition strategies (e.g., nutrient absorption and nutrient resorption) associated with plant growth, particularly under changing soil environments. A greenhouse experiment was performed with seedlings of Pinus elliottii Englem and conditioned soils of monoculture plantations (P. elliottii and Cunninghamia lanceolata Hook). Soil sterilization was designed to test plant phosphorus (P) acquisition strategy with and without native soil fungal communities. Soils from P. elliottii and C. lanceolata plantations were used to explore the specific soil legacy effects on two different P acquisition pathways (absorption and resorption). Phosphorus addition was also applied to examine the separate and combined effects of soil abiotic factors and soil fungal factors on P acquisition pathways. Due to diminished mycorrhizal symbiosis, PSF prompted plants to increasingly rely on P resorption under soil sterilization. In contrast, P absorption was employed preferentially in the heterospecific soil, where species-specific pathogenic fungi could not affect P absorption. Higher soil P availability diluted the effects of soil fungal factors on the trade-off between the two P acquisition pathways in terms of the absolute PSF. Moreover, P addition plays a limited role in terms of the relative PSF and does not affect the direction and strength of relative PSF. Our results reveal the role of PSF in regulating plant P acquisition pathways and highlight the interaction between mycorrhizal and pathogenic fungi as the underlying mechanism of PSF.
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Affiliation(s)
- Ning Ma
- National Ecosystem Science Data Center, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- Sino-Danish Center for Education and Research, Eastern Yanqihu Campus, University of Chinese Academy of Sciences, 380 Huaibeizhuang, Beijing 101400, China
| | - Liang Kou
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Shenggong Li
- National Ecosystem Science Data Center, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- Sino-Danish Center for Education and Research, Eastern Yanqihu Campus, University of Chinese Academy of Sciences, 380 Huaibeizhuang, Beijing 101400, China
| | - Xiaoqin Dai
- Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Shengwang Meng
- Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Lei Jiang
- National Ecosystem Science Data Center, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Yafang Xue
- National Ecosystem Science Data Center, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiajia Zheng
- National Ecosystem Science Data Center, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoli Fu
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Huimin Wang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
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4
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Cappelli SL, Pichon NA, Mannall T, Allan E. Partitioning the effects of plant diversity on ecosystem functions at different trophic levels. ECOL MONOGR 2022. [DOI: 10.1002/ecm.1521] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Seraina L. Cappelli
- Institute of Plant Sciences University of Bern Altenbergrain 21 Bern Switzerland
- Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences University of Helsinki
| | - Noémie A. Pichon
- Institute of Plant Sciences University of Bern Altenbergrain 21 Bern Switzerland
- Department of Ecology and Genetics University of Oulu Oulu Finland
| | - Tosca Mannall
- Institute of Plant Sciences University of Bern Altenbergrain 21 Bern Switzerland
| | - Eric Allan
- Institute of Plant Sciences University of Bern Altenbergrain 21 Bern Switzerland
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5
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Nutrients and consumers impact tree colonization differently from performance in a successional old field. Oecologia 2022; 198:219-227. [DOI: 10.1007/s00442-021-05096-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/12/2021] [Indexed: 10/19/2022]
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6
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Xu X, Zhang Y, Li S, Chen H, Liu M, Li B, Nie M. Native herbivores indirectly facilitate the growth of invasive Spartina in a eutrophic saltmarsh. Ecology 2021; 103:e3610. [PMID: 34923622 DOI: 10.1002/ecy.3610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 09/21/2021] [Accepted: 10/07/2021] [Indexed: 11/07/2022]
Abstract
Current theory (e.g., consumer-controlled theory) predicts that nutrient enrichment typically amplifies herbivory and thereby suppresses the growth and expansion of invasive plants. Herbivores can facilitate plant regrowth in the native community by stimulating complementary growth or ameliorating habitat conditions (e.g., by increasing soil oxygen and nutrient availability), but whether they have similar positive effects on invasive plants, especially under nutrient enrichment, remains unknown. Using a field nitrogen (N)-enrichment X crab exclusion experiment, we evaluated and compared the effects of both N enrichment and crab herbivory on the growth performance of a global invasive cordgrass, Spartina alterniflora, and a co-occurring native plant, Phragmites australis. We found that crabs consistently suppressed P. australis by decreasing density and aboveground biomass regardless of N enrichment. In contrast, for S. alterniflora, the negative effects of crabs under ambient N were replaced by positive effects under N enrichment, with crabs stimulating complementary increases in density and aboveground biomass. The differing effects between the N treatments were driven by crab burrowing activity, which increased soil N availability, and the nutrient-use efficiency of S. alterniflora. Our findings reveal that native herbivores can have opposing effects on native and invasive plants, which broadens our understanding of how exotic plants can achieve dominance in a changing world. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Xiao Xu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Yan Zhang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Songshuo Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Hongyang Chen
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Mu Liu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Bo Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
| | - Ming Nie
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China
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7
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Brown A, Heckman RW. Light alters the impacts of nitrogen and foliar pathogens on the performance of early successional tree seedlings. PeerJ 2021; 9:e11587. [PMID: 34285829 PMCID: PMC8272923 DOI: 10.7717/peerj.11587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 05/20/2021] [Indexed: 11/24/2022] Open
Abstract
Light limitation is a major driver of succession and an important determinant of the performance of shade-intolerant tree seedlings. Shade intolerance may result from a resource allocation strategy characterized by rapid growth and high metabolic costs, which may make shade-intolerant species particularly sensitive to nutrient limitation and pathogen pressure. In this study, we evaluated the degree to which nitrogen availability and fungal pathogen pressure interact to influence plant performance across different light environments. To test this, we manipulated nitrogen availability (high, low) and access by foliar fungal pathogens (sprayed with fungicide, unsprayed) to seedlings of the shade-intolerant tree, Liquidambar styraciflua, growing at low and high light availability, from forest understory to adjacent old field. Foliar fungal damage varied with light and nitrogen availability; in low light, increasing nitrogen availability tripled foliar damage, suggesting that increased nutrient availability in low light makes plants more susceptible to disease. Despite higher foliar damage under low light, spraying fungicide to exclude pathogens promoted 14% greater plant height only under high light conditions. Thus, although nitrogen availability and pathogen pressure each influenced aspects of plant performance, these effects were context dependent and overwhelmed by light limitation. This suggests that failure of shade-intolerant species to invade closed-canopy forest can be explained by light limitation alone.
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Affiliation(s)
- Alexander Brown
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States of America.,Curriculum for the Environment and Ecology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States of America
| | - Robert W Heckman
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States of America.,Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America
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8
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Gao FL, He QS, Xie RQ, Hou JH, Shi CL, Li JM, Yu FH. Interactive effects of nutrient availability, fluctuating supply, and plant parasitism on the post-invasion success of Bidens pilosa. Biol Invasions 2021. [DOI: 10.1007/s10530-021-02555-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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9
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Ni M, Deane DC, Li S, Wu Y, Sui X, Xu H, Chu C, He F, Fang S. Invasion success and impacts depend on different characteristics in non‐native plants. DIVERS DISTRIB 2021. [DOI: 10.1111/ddi.13267] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Ming Ni
- Department of Ecology State Key Laboratory of Biocontrol and School of Life Sciences Sun Yat‐sen University Guangzhou China
| | - David C. Deane
- Department of Renewable Resources University of Alberta Edmonton Alberta Canada
| | - Shaopeng Li
- School of Ecological and Environmental Sciences East China Normal University Shanghai China
| | - Yingtong Wu
- Department of Biology University of Missouri St. Louis Missouri USA
| | - Xinghua Sui
- Department of Ecology State Key Laboratory of Biocontrol and School of Life Sciences Sun Yat‐sen University Guangzhou China
| | - Han Xu
- Research Institute of Tropical Forestry Chinese Academy of Forestry Guangzhou China
| | - Chengjin Chu
- Department of Ecology State Key Laboratory of Biocontrol and School of Life Sciences Sun Yat‐sen University Guangzhou China
| | - Fangliang He
- Department of Renewable Resources University of Alberta Edmonton Alberta Canada
| | - Suqin Fang
- Department of Ecology State Key Laboratory of Biocontrol and School of Life Sciences Sun Yat‐sen University Guangzhou China
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10
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Welsh ME, Cronin JP, Mitchell CE. Trait-based variation in host contribution to pathogen transmission across species and resource supplies. Ecology 2020; 101:e03164. [PMID: 33460129 DOI: 10.1002/ecy.3164] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 04/24/2020] [Accepted: 06/18/2020] [Indexed: 01/26/2023]
Abstract
Two key knowledge gaps currently limit the development of more predictive and general models of pathogen transmission: (1) the physiological basis of heterogeneity in host contribution to pathogen transmission (reservoir potential) remains poorly understood and (2) a general means of integrating the ecological dynamics of host communities has yet to emerge. If the traits responsible for differences in reservoir potential also modulate host community dynamics, these traits could be used to predict pathogen transmission as host communities change. In two greenhouse experiments, across 23 host species and two levels of resource supply, the reservoir potential of plant hosts increased significantly along the Leaf Economics Spectrum, a global axis of plant physiological trait covariation that features prominently in models of plant community ecology. This indicates that the traits of the Leaf Economics Spectrum underlie broad differences in reservoir potential across host species and resource supplies. Therefore, host traits could be used to integrate epidemiological models of pathogen transmission with ecological models of host community change.
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Affiliation(s)
- Miranda E Welsh
- Thompson Writing Program, Duke University, Durham, North Carolina, 27708, USA.,Environment, Ecology and Energy Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
| | - James Patrick Cronin
- U.S. Geological Survey, Wetland and Aquatic Research Center, 700 Cajundome Boulevard, Lafayette, Louisiana, 70506, USA
| | - Charles E Mitchell
- Environment, Ecology and Energy Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA.,Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
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11
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. Eutrophication, biodiversity loss, and species invasions modify the relationship between host and parasite richness during host community assembly. GLOBAL CHANGE BIOLOGY 2020; 26:4854-4867. [PMID: 32427383 DOI: 10.1111/gcb.15165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 04/02/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Host and parasite richness are generally positively correlated, but the stability of this relationship in response to global change remains poorly understood. Rapidly changing biotic and abiotic conditions can alter host community assembly, which in turn, can alter parasite transmission. Consequently, if the relationship between host and parasite richness is sensitive to parasite transmission, then changes in host composition under various global change scenarios could strengthen or weaken the relationship between host and parasite richness. To test the hypothesis that host community assembly can alter the relationship between host and parasite richness in response to global change, we experimentally crossed host diversity (biodiversity loss) and resource supply to hosts (eutrophication), then allowed communities to assemble. As previously shown, initial host diversity and resource supply determined the trajectory of host community assembly, altering post-assembly host species richness, richness-independent host phylogenetic diversity, and colonization by exotic host species. Overall, host richness predicted parasite richness, and as predicted, this effect was moderated by exotic abundance-communities dominated by exotic species exhibited a stronger positive relationship between post-assembly host and parasite richness. Ultimately, these results suggest that, by modulating parasite transmission, community assembly can modify the relationship between host and parasite richness. These results thus provide a novel mechanism to explain how global environmental change can generate contingencies in a fundamental ecological relationship-the positive relationship between host and parasite richness.
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Affiliation(s)
- Fletcher W Halliday
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Peter A Wilfahrt
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, USA
- Department of Disturbance Ecology, University of Bayreuth, Bayreuth, Germany
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, USA
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12
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Goss EM, Kendig AE, Adhikari A, Lane B, Kortessis N, Holt RD, Clay K, Harmon PF, Flory SL. Disease in Invasive Plant Populations. ANNUAL REVIEW OF PHYTOPATHOLOGY 2020; 58:97-117. [PMID: 32516034 DOI: 10.1146/annurev-phyto-010820-012757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Non-native invasive plants can establish in natural areas, where they can be ecologically damaging and costly to manage. Like cultivated plants, invasive plants can experience a relatively disease-free period upon introduction and accumulate pathogens over time. Diseases of invasive plant populations are infrequently studied compared to diseases of agriculture, forestry, and even native plant populations. We evaluated similarities and differences in the processes that are likely to affect pathogen accumulation and disease in invasive plants compared to cultivated plants, which are the dominant focus of the field of plant pathology. Invasive plants experience more genetic, biotic, and abiotic variation across space and over time than cultivated plants, which is expected to stabilize the ecological and evolutionary dynamics of interactions with pathogens and possibly weaken the efficacy of infectious disease in their control. Although disease is expected to be context dependent, the widespread distribution of invasive plants makes them important pathogen reservoirs. Research on invasive plant diseases can both protect crops and help manage invasive plant populations.
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Affiliation(s)
- Erica M Goss
- Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, Florida 32611, USA;
| | - Amy E Kendig
- Agronomy Department, University of Florida, Gainesville, Florida 32611, USA
| | - Ashish Adhikari
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - Brett Lane
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - Nicholas Kortessis
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Robert D Holt
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Keith Clay
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana 70118, USA
| | - Philip F Harmon
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - S Luke Flory
- Agronomy Department, University of Florida, Gainesville, Florida 32611, USA
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13
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Release from Above- and Belowground Insect Herbivory Mediates Invasion Dynamics and Impact of an Exotic Plant. PLANTS 2019; 8:plants8120544. [PMID: 31779143 PMCID: PMC6963668 DOI: 10.3390/plants8120544] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/19/2019] [Accepted: 11/21/2019] [Indexed: 11/17/2022]
Abstract
The enemy-release hypothesis is one of the most popular but also most discussed hypotheses to explain invasion success. However, there is a lack of explicit, experimental tests of predictions of the enemy-release hypothesis (ERH), particularly regarding the effects of above- and belowground herbivory. Long-term studies investigating the relative effect of herbivores on invasive vs. native plant species within a community are still lacking. Here, we report on a long-term field experiment in an old-field community, invaded by Solidago canadensis s. l., with exclusion of above- and belowground insect herbivores. We monitored population dynamics of the invader and changes in the diversity and functioning of the plant community across eight years. Above- and belowground insects favoured the establishment of the invasive plant species and thereby increased biomass and decreased diversity of the plant community. Effects of invertebrate herbivores on population dynamics of S. canadensis appeared after six years and increased over time, suggesting that long-term studies are needed to understand invasion dynamics and consequences for plant community structure. We suggest that the release from co-evolved trophic linkages is of importance not only for the effect of invasive species on ecosystems, but also for the functioning of novel species assemblages arising from climate change.
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14
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Liu X, Lu Y, Zhang Z, Zhou S. Foliar fungal diseases respond differently to nitrogen and phosphorus additions in Tibetan alpine meadows. Ecol Res 2019. [DOI: 10.1111/1440-1703.12064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiang Liu
- State Key Laboratory of Plateau Ecology and Agriculture Qinghai University Xining PR China
- Ministry of Education Key Laboratory of Western China's Environmental Systems Lanzhou University Lanzhou PR China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering School of Life Sciences, Fudan University Shanghai PR China
| | - Yawen Lu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering School of Life Sciences, Fudan University Shanghai PR China
| | - Zhenhua Zhang
- Key Laboratory of Adaptation and Evolution of Plateau Biota Northwest Institute of Plateau Biology, Chinese Academy of Sciences Xining PR China
| | - Shurong Zhou
- State Key Laboratory of Plateau Ecology and Agriculture Qinghai University Xining PR China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering School of Life Sciences, Fudan University Shanghai PR China
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15
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Heckman RW, Halliday FW, Mitchell CE. A growth–defense trade-off is general across native and exotic grasses. Oecologia 2019; 191:609-620. [DOI: 10.1007/s00442-019-04507-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 09/06/2019] [Indexed: 11/27/2022]
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16
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. Past is prologue: host community assembly and the risk of infectious disease over time. Ecol Lett 2018; 22:138-148. [PMID: 30403005 DOI: 10.1111/ele.13176] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 09/30/2018] [Accepted: 10/05/2018] [Indexed: 12/17/2022]
Abstract
Infectious disease risk is often influenced by host diversity, but the causes are unresolved. Changes in diversity are associated with changes in community structure, particularly during community assembly; therefore, by incorporating change over time, host community assembly may provide a framework to resolve causation. In turn, community assembly can be driven by many processes, including resource enrichment. To test the hypothesis that community assembly causally links host diversity to future disease, we experimentally manipulated host diversity and resource supply to hosts, then allowed communities to assemble for 2 years (surveyed 2012-2014). Initially, host diversity increased disease. Subsequently, host diversity did not directly alter disease. However, host diversity determined the trajectory of host community assembly, altering colonisation by exotic host species and richness-independent host phylogenetic diversity, which together reversed the initial increase in disease. Ultimately, incorporating the temporal dimension of community assembly revealed novel mechanisms linking host diversity to future disease.
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Affiliation(s)
- Fletcher W Halliday
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, 33620, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Peter A Wilfahrt
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, 27599, USA
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17
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. A multivariate test of disease risk reveals conditions leading to disease amplification. Proc Biol Sci 2018; 284:rspb.2017.1340. [PMID: 29046374 DOI: 10.1098/rspb.2017.1340] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/14/2017] [Indexed: 02/06/2023] Open
Abstract
Theory predicts that increasing biodiversity will dilute the risk of infectious diseases under certain conditions and will amplify disease risk under others. Yet, few empirical studies demonstrate amplification. This contrast may occur because few studies have considered the multivariate nature of disease risk, which includes richness and abundance of parasites with different transmission modes. By combining a multivariate statistical model developed for biodiversity-ecosystem-multifunctionality with an extensive field manipulation of host (plant) richness, composition and resource supply to hosts, we reveal that (i) host richness alone could not explain most changes in disease risk, and (ii) shifting host composition allowed disease amplification, depending on parasite transmission mode. Specifically, as predicted from theory, the effect of host diversity on parasite abundance differed for microbes (more density-dependent transmission) and insects (more frequency-dependent transmission). Host diversity did not influence microbial parasite abundance, but nearly doubled insect parasite abundance, and this amplification effect was attributable to variation in host composition. Parasite richness was reduced by resource addition, but only in species-rich host communities. Overall, this study demonstrates that multiple drivers, related to both host community and parasite characteristics, can influence disease risk. Furthermore, it provides a framework for evaluating multivariate disease risk in other systems.
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Affiliation(s)
- Fletcher W Halliday
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Peter A Wilfahrt
- Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.,Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, NC 27599, USA
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18
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Heckman RW, Halliday FW, Wilfahrt PA, Mitchell CE. Effects of native diversity, soil nutrients, and natural enemies on exotic invasion in experimental plant communities. Ecology 2017; 98:1409-1418. [PMID: 28273331 DOI: 10.1002/ecy.1796] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/08/2017] [Accepted: 02/16/2017] [Indexed: 11/05/2022]
Abstract
Many factors can promote exotic plant success. Three of these factors-greater pressure from natural enemies on natives, increased soil nutrient supply, and low native species richness-may interact during invasions. To test for independent and interactive effects of these drivers, we planted herbaceous perennial communities at two levels of native richness (monocultures and five-species polycultures). We then factorially manipulated soil nutrient supply and access to these communities by aboveground foliar enemies (fungal pathogens and insect herbivores), and allowed natural colonization to proceed for four years. We predicted that nutrient addition would increase exotic success, while enemy exclusion and increasing native richness would reduce exotic success. Additionally, we expected that enemy exclusion would reduce the benefits of nutrient addition to exotic species most in species-poor communities, and that this effect would be weaker in species-rich communities. In total, we found no evidence that nutrient supply, enemy access, and native richness interacted to influence exotic success. Furthermore, native richness had no effect on exotic success. Instead, nutrient addition increased, and enemy exclusion decreased, exotic success independently. As predicted, enemy exclusion reduced exotic success, primarily by slowing the decline in abundance of planted native species. Together, these results demonstrate that multiple drivers of exotic success can act independently within a single system.
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Affiliation(s)
- Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599, USA
| | - Fletcher W Halliday
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599, USA
| | - Peter A Wilfahrt
- Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, North Carolina, 27599, USA
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599, USA.,Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, North Carolina, 27599, USA
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19
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Abstract
Plant-herbivore interactions shape community dynamics across marine, freshwater, and terrestrial habitats. From amphipods to elephants and from algae to trees, plant-herbivore relationships are the crucial link generating animal biomass (and human societies) from mere sunlight. These interactions are, thus, pivotal to understanding the ecology and evolution of virtually any ecosystem. Here, we briefly highlight recent advances in four areas of plant-herbivore interactions: (1) plant defense theory, (2) herbivore diversity and ecosystem function, (3) predation risk aversion and herbivory, and (4) how a changing climate impacts plant-herbivore interactions. Recent advances in plant defense theory, for example, highlight how plant life history and defense traits affect and are affected by multiple drivers, including enemy pressure, resource availability, and the local plant neighborhood, resulting in trait-mediated feedback loops linking trophic interactions with ecosystem nutrient dynamics. Similarly, although the positive effect of consumer diversity on ecosystem function has long been recognized, recent advances using DNA barcoding to elucidate diet, and Global Positioning System/remote sensing to determine habitat selection and impact, have shown that herbivore communities are probably even more functionally diverse than currently realized. Moreover, although most diversity-function studies continue to emphasize plant diversity, herbivore diversity may have even stronger impacts on ecosystem multifunctionality. Recent studies also highlight the role of risk in plant-herbivore interactions, and risk-driven trophic cascades have emerged as landscape-scale patterns in a variety of ecosystems. Perhaps not surprisingly, many plant-herbivore interactions are currently being altered by climate change, which affects plant growth rates and resource allocation, expression of chemical defenses, plant phenology, and herbivore metabolism and behavior. Finally, we conclude by noting that although the field is advancing rapidly, the world is changing even more rapidly, challenging our ability to manage these pivotal links in the food chain.
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Affiliation(s)
- Deron E. Burkepile
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
- Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA, USA
| | - John D. Parker
- Smithsonian Environmental Research Center, Edgewater, MD, USA
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