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Santamaría J, Tomas F, Ballesteros E, Ruiz JM, Bernardeau-Esteller J, Terrados J, Cebrian E. The role of competition and herbivory in biotic resistance against invaders: a synergistic effect. Ecology 2021; 102:e03440. [PMID: 34143423 DOI: 10.1002/ecy.3440] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 04/05/2021] [Indexed: 11/08/2022]
Abstract
Invasive species pose a major threat to global diversity, and once they are well established their eradication typically becomes unfeasible. However, certain natural mechanisms can increase the resistance of native communities to invaders and can be used to guide effective management policies. Both competition and herbivory have been identified as potential biotic resistance mechanisms that can limit plant invasiveness, but it is still under debate to what extent they might be effective against well-established invaders. Surprisingly, whereas biotic mechanisms are known to interact strongly, most studies to date have examined single biotic mechanisms separately, which likely influences our understanding of the strength and effectiveness of biotic resistance against invaders. Here we use long-term field data, benthic assemblage sampling, and exclusion experiments to assess the effect of native assemblage complexity and herbivory on the invasion dynamics of a successful invasive species, the alga Caulerpa cylindracea. A higher complexity of the native algal assemblage limited C. cylindracea invasion, probably through competition by canopy-forming and erect algae. Additionally, high herbivory pressure by the fish Sarpa salpa reduced C. cylindracea abundance by more than four times. However, long-term data of the invasion reflects that biotic resistance strength can vary across the invasion process and it is only where high assemblage complexity is concomitant with high herbivory pressure, that the most significant limitation is observed (synergistic effect). Overall, the findings reported in this study highlight that neglecting the interactions between biotic mechanisms during invasive processes and restricting the studied time scales may lead to underestimations of the true capacity of native assemblages to develop resistance to invaders.
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Affiliation(s)
- Jorge Santamaría
- Marine Resources and Biodiversity Research Group (GRMAR), Institute of Aquatic Ecology, University of Girona, Girona, 17003, Catalonia, Spain
| | - Fiona Tomas
- Marine Ecosystems Dynamics Group-Instituto Mediterráneo de Estudios Avanzados (IMEDEA), Universitat de les Illes Balears (UIB)-Consejo Superior de Investigaciones Científicas (CSIC), Esporles, 07190, Balearic Islands, Spain
| | - Enric Ballesteros
- Centre d'Estudis Avançats de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, 17300, Catalonia, Spain
| | - Juan M Ruiz
- Seagrass Ecology Group-Centro Oceanográfico de Murcia, Instituto Español de Oceanografía (IEO), San Pedro del Pinatar, 30740, Murcia, Spain
| | - Jaime Bernardeau-Esteller
- Seagrass Ecology Group-Centro Oceanográfico de Murcia, Instituto Español de Oceanografía (IEO), San Pedro del Pinatar, 30740, Murcia, Spain
| | - Jorge Terrados
- Marine Ecosystems Dynamics Group-Instituto Mediterráneo de Estudios Avanzados (IMEDEA), Universitat de les Illes Balears (UIB)-Consejo Superior de Investigaciones Científicas (CSIC), Esporles, 07190, Balearic Islands, Spain
| | - Emma Cebrian
- Centre d'Estudis Avançats de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, 17300, Catalonia, Spain
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Dodge VJ, Eviner VT, Cushman JH. Context-dependent effects of a reintroduced ungulate on soil properties are driven by soil texture, moisture, and herbivore activity. Ecol Evol 2020; 10:10858-10871. [PMID: 33072301 PMCID: PMC7548165 DOI: 10.1002/ece3.6743] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/03/2020] [Accepted: 08/10/2020] [Indexed: 11/08/2022] Open
Abstract
Although there is considerable evidence that large mammalian herbivores influence ecosystem-level processes, studies have reported such widely varying results that generalizations have remained elusive. Here, we use an 18-year-old exclosure experiment-stratified across a landscape heterogeneous with respect to soil texture, moisture and herbivore activity-to understand the variable effects of tule elk (Cervus canadensis nannodes), a native reintroduced herbivore, on soil properties along the coast of northern California. Elk significantly increased soil bulk density and created a compacted layer at shallow soil depth, while decreasing infiltration rate and pH. The effects of elk on bulk density, penetration resistance, and pH varied with soil type, being least pronounced in coarse, sandy loams, and greatest in loose sand. The effects of elk on nutrient availability varied along gradients of soil texture and moisture. In coarser soils, elk decreased ammonium availability, but increased it in finer soils. Elk also decreased soil moisture content, in part through their positive effect on bulk density, and this effect was most pronounced in coarser soils. Through decreasing soil moisture content, elk also decreased nitrate availability in coarser soils. At greater levels of elk activity (as measured by dung deposition), the elk effect on bulk density was amplified, and this had a corresponding negative effect on nitrate and phosphate availability. Our study has demonstrated that a better understanding of spatial variation in the effects of herbivores on ecosystems can emerge by evaluating their influences across gradients of soil texture, soil moisture, and herbivore activity. These data enabled us to evaluate several frameworks that have been developed to understand the variable effects of herbivores on ecosystems, which is a significant step in reconciling the many competing ideas put forth to explain the context-dependent effects of large herbivores on grazed ecosystems.
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Affiliation(s)
- Vanessa J Dodge
- Department of Biology Sonoma State University Rohnert Park CA USA
| | - Valerie T Eviner
- Department of Plant Sciences University of California Davis CA USA
| | - J Hall Cushman
- Department of Natural Resources & Environmental Science University of Nevada Reno NV USA
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3
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Forest disturbances promote invasion of alien herbaceous plants: a comparison of abundance and plant traits between alien and native species in thinned and unthinned stands. Biol Invasions 2020. [DOI: 10.1007/s10530-020-02283-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Scott R, Gras R. A simulation study shows impacts of genetic diversity on establishment success of digital invaders in heterogeneous environments. Ecol Modell 2020. [DOI: 10.1016/j.ecolmodel.2020.109173] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Forbes ES, Cushman JH, Burkepile DE, Young TP, Klope M, Young HS. Synthesizing the effects of large, wild herbivore exclusion on ecosystem function. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13376] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elizabeth S. Forbes
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - J. Hall Cushman
- Department of Natural Resources and Environmental Science University of Nevada – Reno Reno Nevada
| | - Deron E. Burkepile
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences University of California, Davis Davis California
| | - Maggie Klope
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
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6
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Cecil EM, Spasojevic MJ, Cushman JH. Cascading effects of mammalian herbivores on ground-dwelling arthropods: Variable responses across arthropod groups, habitats and years. J Anim Ecol 2019; 88:1319-1331. [PMID: 31135962 DOI: 10.1111/1365-2656.13033] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 05/16/2019] [Indexed: 11/27/2022]
Abstract
Large mammalian herbivores are well known to shape the structure and function of ecosystems world-wide, and these effects can in turn cascade through systems to indirectly influence other animal species. A wealth of studies has explored the effects of large mammals on arthropods, but to date they have reported such widely varying results that generalizations have been elusive. Three factors are likely drivers of this variability: the widely varying life-history characteristics of different arthropod groups, the highly variable landscapes that mammalian herbivores commonly inhabit and temporal variation in environmental conditions. Here, we use an 18-year-old exclosure experiment stratified across three distinct coastal prairie habitats in northern California to address the effects of a reintroduced mammalian herbivore, tule elk (Cervus canadensis nannodes) on the composition, richness and abundance of ground-dwelling arthropods over two years with very different precipitation regimes. We found that elk shifted the composition of arthropod communities, increasing the abundance of ants, beetles, spiders and mites, decreasing the abundance of woodlice and bristletails in some but not all habitats types, and having no effect on the abundance of bugs, crickets and springtails. Elk also increased richness and changed the composition of ant genera and beetle morpho-species. Interestingly, the effects of elk on arthropod composition, richness and abundance varied little between years, despite very different precipitation levels, biomass accumulation and thatch height. Elk reduced shrub cover, above-ground herbaceous biomass and thatch height and increased soil compaction, and these changes predicted the abundance and richness of arthropods, although taxonomic groups varied in their responses, presumably due to differences in environmental requirements. Synthesis. Our research highlights the importance of using long-term experiments to assess the cascading effects of large herbivores on the composition of grounddwelling arthropod communities and to identify the mechanisms that indirectly shape arthropod responses to herbivores among variable habitats and years in order to develop a greater understanding of the variable responses of arthropods to large mammalian herbivores.
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Affiliation(s)
- Eric M Cecil
- Department of Biology, Sonoma State University, Rohnert Park, California
| | - Marko J Spasojevic
- Department of Evolution, Ecology, and Organismal Biology, University of California - Riverside, Riverside, California
| | - J Hall Cushman
- Department of Natural Resources & Environmental Science, University of Nevada, Reno, Nevada
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Ellis TD, Cushman JH. Indirect effects of a large mammalian herbivore on small mammal populations: Context-dependent variation across habitat types, mammal species, and seasons. Ecol Evol 2018; 8:12115-12125. [PMID: 30598804 PMCID: PMC6303759 DOI: 10.1002/ece3.4670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 09/12/2018] [Accepted: 09/13/2018] [Indexed: 11/28/2022] Open
Abstract
Multiple consumer species frequently co-occur in the same landscape and, through effects on surrounding environments, can interact in direct and indirect ways. These interactions can vary in occurrence and importance, and focusing on this variation is critical for understanding the dynamics of interactions among consumers. Large mammalian herbivores are important engineers of ecosystems worldwide, have substantial impacts on vegetation, and can indirectly affect small-mammal populations. However, the degree to which such indirect effects vary within the same system has received minimal attention. We used a 16-year-old exclosure experiment, stratified across a heterogeneous landscape, to evaluate the importance of context-dependent interactions between tule elk (Cervus canadensis nannodes) and small mammals (deer mice [Peromyscus maniculatus], meadow voles [Microtus californicus], and harvest mice [Reithrodontymys megalotis]) in a coastal grassland in California. Effects of elk on voles varied among habitats and seasons: In open grasslands, elk reduced vole numbers during fall 2013 but not summer 2014; in Lupinus-dominated grasslands, elk reduced vole numbers during summer 2014 but not fall 2013; and in Baccharis-dominated grasslands, elk had no effect on vole numbers in either season. Effects of elk on the two mice species also varied among habitats and seasons, but often in different ways from voles and each other. In fall 2013, elk decreased mice abundances in Lupinus-dominated grasslands, but not in Baccharis-dominated or open grasslands. In summer 2014, elk decreased the abundance of harvest mice consistently across habitat types. In contrast, elk increased deer-mice numbers in open grasslands but not other habitats. Within the same heterogenous study system, the influence of elk on small mammals was strongly context-dependent, varying among habitats, mammal species, and seasons. We hypothesize that such variability is common in nature and that failure to consider it may yield inaccurate findings and limit our understanding of interactions among co-occurring consumers.
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Affiliation(s)
- Taylor D. Ellis
- Department of BiologySonoma State UniversityRohnert ParkCalifornia
- Present address:
Point Reyes National SeashoreCalifornia
| | - J. Hall Cushman
- Department of Natural Resources and Environmental ScienceUniversity of NevadaRenoNevada
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Derham TT, Duncan RP, Johnson CN, Jones ME. Hope and caution: rewilding to mitigate the impacts of biological invasions. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2018.0127. [PMID: 30348875 DOI: 10.1098/rstb.2018.0127] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2018] [Indexed: 12/31/2022] Open
Abstract
Rewilding is a novel approach to ecological restoration. Trophic rewilding in particular aims to reinstate ecological functions, especially trophic interactions, through the introduction of animals. We consider the potential for trophic rewilding to address biological invasions. In this broad review, we note some of the important conceptual and ethical foundations of rewilding, including a focus on ecosystem function rather than composition, reliance on animal agency, and an appeal to an ethic of coexistence. Second, we use theory from invasion biology to highlight pathways by which rewilding might prevent or mitigate the impacts of an invasion, including increasing biotic resistance. Third, we use a series of case studies to illustrate how reintroductions can mitigate the impacts of invasions. These include reintroductions and positive management of carnivores and herbivores including European pine martens (Martes martes), Eurasian otters (Lutra lutra), dingoes (Canis dingo), Tasmanian devils (Sarcophilus harrisii) and tule elk (Cervus canadensis nannodes). Fourth, we consider the risk that rewilding may enable a biological invasion or aggravate its impacts. Lastly, we highlight lessons that rewilding science might take from invasion biology.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.
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Affiliation(s)
- Tristan T Derham
- School of Natural Sciences and Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH), University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Richard P Duncan
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory, Australia
| | - Christopher N Johnson
- School of Natural Sciences and Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH), University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Menna E Jones
- School of Natural Sciences, University of Tasmania, Hobart, Tasmania, Australia
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Zhang Y, Meng H, Wang Y, He Q. Herbivory enhances the resistance of mangrove forest to cordgrass invasion. Ecology 2018; 99:1382-1390. [DOI: 10.1002/ecy.2233] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 02/14/2018] [Accepted: 03/19/2018] [Indexed: 01/27/2023]
Affiliation(s)
- Yihui Zhang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems College of Environment and Ecology Xiamen University Xiamen Fujian 361102 China
| | - Hanyu Meng
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems College of Environment and Ecology Xiamen University Xiamen Fujian 361102 China
| | - Yi Wang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems College of Environment and Ecology Xiamen University Xiamen Fujian 361102 China
- Department of Earth, Environmental and Geographic Sciences University of British Columbia, Okanagan 1177 Research Road Kelowna British Columbia V1V1V7 Canada
| | - Qiang He
- Division of Marine Science and Conservation Nicholas School of the Environment Duke University 135 Duke Marine Lab Road Beaufort North Carolina 28516 USA
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Ender CL, Christian CE, Cushman JH. Native herbivores and environmental heterogeneity as mediators of an exotic grass invasion. Ecol Evol 2017; 7:1561-1571. [PMID: 28261465 PMCID: PMC5330880 DOI: 10.1002/ece3.2727] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 12/07/2016] [Accepted: 12/18/2016] [Indexed: 11/23/2022] Open
Abstract
Given that many exotic plant species throughout the world are having large ecological and economic effects, it is vital to understand the forces that mediate their success in novel landscapes. Both native herbivores and recipient ecosystems can have substantial effects on the performance of exotic plant species, and may interact with each other or vary in their effects over time. Unfortunately, few studies have evaluated the importance of these kinds of context-dependent effects. Here, we use a 17-year-old exclosure experiment stratified across a coastal grassland in northern California to address the relative importance of a reintroduced mammalian herbivore, tule elk (Cervus canadensis nannodes), and environmental heterogeneity in mediating the growth, abundance, and recruitment of a problematic grass invader, Holcus lanatus. We found that elk reduced Holcus abundance, aboveground biomass, percent cover, frequency, and seedling recruitment, but that these effects often varied among habitat types, with effects being greater in open grasslands than shrub-dominated grasslands. The performance of Holcus populations also varied significantly among habitat types, with the invader usually having the greatest success in Baccharis-dominated grasslands. Our results suggest that environmental heterogeneity had much greater influence on Holcus success than elk, and that these effects were due largely to soil pH and moisture. The negative effects of elk on Holcus appeared after 4 years and did not intensify after an additional 13 years. Furthermore, despite their negative effects, these prominent herbivores did not prevent the spread of Holcus into previously uninvaded areas. Our research highlights the importance of assessing the individual and interactive effects of native herbivores and environmental heterogeneity on the success of invasive, exotic plant species. It emphasizes the reality that the negative effects of herbivores on exotic plant species will often vary across heterogeneous landscapes and may be insufficient to prevent the expansion of these invaders.
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Affiliation(s)
- Cody L. Ender
- Department of BiologySonoma State UniversityRohnert ParkCAUSA
| | - Caroline E. Christian
- Department of Environmental Studies & PlanningSonoma State UniversityRohnert ParkCAUSA
| | - J. Hall Cushman
- Department of BiologySonoma State UniversityRohnert ParkCAUSA
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