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Attempting to predict the plant-mediated trophic effects of soil salinity: A mechanistic approach to supplementing insufficient information. FOOD WEBS 2017. [DOI: 10.1016/j.fooweb.2017.02.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Vidal MC, Murphy SM. Bottom‐up vs. top‐down effects on terrestrial insect herbivores: a meta‐analysis. Ecol Lett 2017; 21:138-150. [DOI: 10.1111/ele.12874] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/03/2017] [Accepted: 10/04/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Mayra C. Vidal
- Department of Biological Sciences University of Denver Denver CO USA
| | - Shannon M. Murphy
- Department of Biological Sciences University of Denver Denver CO USA
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Cheng BS, Grosholz ED. Environmental stress mediates trophic cascade strength and resistance to invasion. Ecosphere 2016. [DOI: 10.1002/ecs2.1247] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Brian S. Cheng
- Bodega Marine Laboratory University of California, Davis 2099 Westside Road Bodega Bay California 94923 USA
- Department of Environmental Science and Policy University of California, Davis One Shields Avenue Davis California 95616 USA
| | - Edwin D. Grosholz
- Bodega Marine Laboratory University of California, Davis 2099 Westside Road Bodega Bay California 94923 USA
- Department of Environmental Science and Policy University of California, Davis One Shields Avenue Davis California 95616 USA
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Meunier CL, Gundale MJ, Sánchez IS, Liess A. Impact of nitrogen deposition on forest and lake food webs in nitrogen-limited environments. GLOBAL CHANGE BIOLOGY 2016; 22:164-79. [PMID: 25953197 DOI: 10.1111/gcb.12967] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 03/26/2015] [Accepted: 04/29/2015] [Indexed: 05/09/2023]
Abstract
Increased reactive nitrogen (Nr ) deposition has raised the amount of N available to organisms and has greatly altered the transfer of energy through food webs, with major consequences for trophic dynamics. The aim of this review was to: (i) clarify the direct and indirect effects of Nr deposition on forest and lake food webs in N-limited biomes, (ii) compare and contrast how aquatic and terrestrial systems respond to increased Nr deposition, and (iii) identify how the nutrient pathways within and between ecosystems change in response to Nr deposition. We present that Nr deposition releases primary producers from N limitation in both forest and lake ecosystems and raises plants' N content which in turn benefits herbivores with high N requirements. Such trophic effects are coupled with a general decrease in biodiversity caused by different N-use efficiencies; slow-growing species with low rates of N turnover are replaced by fast-growing species with high rates of N turnover. In contrast, Nr deposition diminishes below-ground production in forests, due to a range of mechanisms that reduce microbial biomass, and decreases lake benthic productivity by switching herbivore growth from N to phosphorus (P) limitation, and by intensifying P limitation of benthic fish. The flow of nutrients between ecosystems is expected to change with increasing Nr deposition. Due to higher litter production and more intense precipitation, more terrestrial matter will enter lakes. This will benefit bacteria and will in turn boost the microbial food web. Additionally, Nr deposition promotes emergent insects, which subsidize the terrestrial food web as prey for insectivores or by dying and decomposing on land. So far, most studies have examined Nr -deposition effects on the food web base, whereas our review highlights that changes at the base of food webs substantially impact higher trophic levels and therefore food web structure and functioning.
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Affiliation(s)
- Cédric L Meunier
- Department of Ecology and Environmental Sciences, Umeå University, 901 87, Umeå, Sweden
| | - Michael J Gundale
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, 901 83, Sweden
| | - Irene S Sánchez
- Department of Ecology and Environmental Sciences, Umeå University, 901 87, Umeå, Sweden
| | - Antonia Liess
- Department of Ecology and Environmental Sciences, Umeå University, 901 87, Umeå, Sweden
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The interactive effects of pulsed grazing disturbance and patch size vary among wetland arthropod guilds. PLoS One 2013; 8:e76672. [PMID: 24116133 PMCID: PMC3792878 DOI: 10.1371/journal.pone.0076672] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/27/2013] [Indexed: 12/04/2022] Open
Abstract
Pulse disturbances and habitat patch size can determine community composition independently or in concert, and may be particularly influential on small spatial scales for organisms with low mobility. In a field experiment, we investigated whether the effects of a pulsed disturbance that simulated a grazing event varied with habitat patch size. We focused on the short-term responses of multiple co-occurring emergent salt marsh arthropods with differing levels of mobility and dispersal potential. As part of a marsh restoration project, two types of emergent marsh structures were created: small circular mounds (0.5 m diameter) separated by several meters of aquatic habitat, and larger, elongated terraces (>50 m long). Study plots (0.25 m2) were established on both structures; in a subset of plots, we simulated a pulsed grazing disturbance event by clipping the aboveground tissue of emergent plants, primarily Spartina alterniflora. At the end of the two-month recovery period, Ischnodemus (Hemiptera: Blissidae) density was over 50% lower in disturbed treatments within both large (terrace) and small (mound) patches. Predatory spider treatment responses were similar to Ischnodemus responses, suggesting a trophic relationship between those two arthropod groups. Alternatively, spiders may have been directly affected by the loss of shelter in the disturbed plots. Prokelisia (Homoptera: Delphacidae), which are generally more mobile than Ischnodemus, were not affected by disturbance treatment or by patch size, suggesting the potential for rapid recolonization following disturbance. Larval stem borers decreased by an order of magnitude in disturbed plots, but only in the large patches. In general, the disturbance effects of vegetation removal on arthropod density and community composition were stronger than patch size effects, and there were few interactions between pulsed disturbance and patch size. Rather, emergent marsh arthropod responses to disturbance and habitat area treatments were linked to the dispersal potential and mobility of each individual taxon.
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Bracken MES, Jones E, Williams SL. Herbivores, tidal elevation, and species richness simultaneously mediate nitrate uptake by seaweed assemblages. Ecology 2011; 92:1083-93. [PMID: 21661569 DOI: 10.1890/10-1374.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In order for research into the consequences of biodiversity changes to be more applicable to real-world ecosystems, experiments must be conducted in the field, where a variety of factors other than diversity can affect the rates of key biogeochemical and physiological processes. Here, we experimentally evaluate the effects of two factors known to affect the diversity and composition of intertidal seaweed assemblages--tidal elevation and herbivory--on nitrate uptake by those assemblages. Based on surveys of community composition at the end of a 1.5-year press experiment, we found that both tide height and herbivores affected seaweed community structure. Not surprisingly, seaweed species richness was greater at lower tidal elevations. Herbivores did not affect richness, but they altered the types of species that were present; seaweed species characterized by higher rates of nitrate uptake were more abundant in herbivore-removal plots. Both tide height and herbivores affected nitrate uptake by seaweed assemblages. Individual seaweed species, as well as entire seaweed assemblages, living higher on the shore had greater rates of biomass-specific nitrate uptake, particularly at high ambient nitrate concentrations. Grazed seaweed assemblages exhibited reduced nitrate uptake, but only at low nitrate concentrations. We evaluated the effect of seaweed richness on nitrate uptake, both alone and after accounting for effects of tidal elevation and herbivores. When only richness was considered, we found no effect on uptake. However, when simultaneous effects of richness, tide height, and herbivores on uptake were evaluated, we found that all three had relatively large and comparable effects on nitrate uptake coefficients and that there was a negative relationship between seaweed richness and nitrate uptake. Particularly because effects of richness on uptake were not apparent unless the effects of tide height and herbivory were also considered, these results highlight the importance of considering the effects of environmental context when evaluating the consequences of biodiversity change in more realistic systems.
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Affiliation(s)
- Matthew E S Bracken
- Marine Science Center, Northeastern University, 430 Nahant Road, Nahant, Massachusetts 01908, USA.
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Nutrient supply and bird predation additively control insect herbivory and tree growth in two contrasting forest habitats. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2009.17862.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Altfeld L, Stiling P. Effects of aphid-tending Argentine ants, nitrogen enrichment and early-season herbivory on insects hosted by a coastal shrub. Biol Invasions 2008. [DOI: 10.1007/s10530-008-9223-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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9
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Van Zandt PA. Plant defense, growth, and habitat: a comparative assessment of constitutive and induced resistance. Ecology 2007; 88:1984-93. [PMID: 17824430 DOI: 10.1890/06-1329.1] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The growth rate (GR) hypothesis relates the evolution of plant defense to resource availability and predicts that plants that have evolved in abiotically stressful environments grow inherently more slowly and are more constitutively resistant to herbivory than plants from more productive habitats. Stress-adapted plants are also predicted to have reduced inducibility, but this prediction has not been previously tested. To evaluate this hypothesis, I compared the growth of nine species of herbaceous plants from Missouri glade habitats to congeners from more productive non-glade habitats. I also conducted bioassays using larvae of the generalist herbivore Spodoptera exigua to estimate constitutive and inducible resistance in these congeners. Glade congeners tended to grow more slowly and have higher constitutive resistance and lower inducibility than non-glade species. However, none of these comparisons was statistically significant due to the conflicting response of one congeneric pair (Salvia azurea and S. lyrata). Analyses without this genus were consistent with the GR hypothesis, as were analyses that categorized congeners by relative growth rate. These results highlight the complexity in searching for factors that determine plant growth rates and resistance traits across multiple genera and support the hypothesis that both constitutive and induced resistance may be influenced by selection on traits that alter plant growth rates. Future studies should attempt to determine whether variation in inducibility is better explained by habitat or relative plant growth rates.
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Affiliation(s)
- Peter A Van Zandt
- Washington University, Department of Biology, I Brookings, Campus Box 1137, St. Louis, Missouri 63130, USA.
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Abstract
Insectivorous birds and ants co-occur in most terrestrial communities, and theory predicts that emergent properties (i.e., nonadditive effects) can determine their combined influence on arthropods and plants. In a three-year factorial experiment, I investigated whether the effects of birds on pine and its arthropods differed based on the presence of ants that were predators of most arthropods, but mutualists with tended aphid species. Birds and ants reduced the abundance of most herbivorous and carnivorous arthropods in an additive fashion, with the effects of ants being stronger than those of birds. In sharp contrast, the opposing influences of birds and ants on tended aphid species interacted strongly; ants only increased tended aphid abundance in the absence of birds, while birds only reduced their abundance in the presence of ants. This interaction was mirrored in total herbivore abundance because tended aphids dominated the herbivore community. I develop a novel lexicon to discuss the emergent properties from these effects of opposing sign (predation, mutualism). Despite having emergent effects on herbivores, birds indirectly increased pine wood and foliage growth to a similar extent whether or not ants were present, while ants had no detectable effects. Birds also indirectly increased the abundance of some pine phloem monoterpenes, but these effects differed based on the presence or absence of ants. Thus, I report on a novel yet possibly widespread indirect interaction between intraguild predators, herbivore mutualists, and plant traits (growth, secondary chemistry) mediated through a species-rich community of arthropods.
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Affiliation(s)
- Kailen A Mooney
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado 80309-0334, USA.
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Abstract
Historically, terrestrial food web theory has been compartmentalized into interactions among aboveground or belowground communities. In this study we took a more synthetic approach to understanding food web interactions by simultaneously examining four trophic levels and investigating how nutrient (nitrogen and carbon) and detrital subsidies impact the ability of the belowground microbial community to alter the abundance of aboveground arthropods (herbivores and predators) associated with the intertidal cord grass Spartina alterniflora. We manipulated carbon, nitrogen, and detrital resources in a field experiment and measured decomposition rate, soil nitrogen pools, plant biomass and quality, herbivore density, and arthropod predator abundance. Because carbon subsidies impact plant growth only indirectly (microbial pathways), whereas nitrogen additions both directly (plant uptake) and indirectly (microbial pathways) impact plant primary productivity, we were able to assess the effect of both belowground soil microbes and nutrient availability on aboveground herbivores and their predators. Herbivore density in the field was suppressed by carbon supplements. Carbon addition altered soil microbial dynamics (net potential ammonification, litter decomposition rate, DON [dissolved organic N] concentration), which limited inorganic soil nitrogen availability and reduced plant size as well as predator abundance. Nitrogen addition enhanced herbivore density by increasing plant size and quality directly by increasing inorganic soil nitrogen pools, and indirectly by enhancing microbial nitrification. Detritus adversely affected aboveground herbivores mainly by promoting predator aggregation. To date, the effects of carbon and nitrogen subsidies on salt marshes have been examined as isolated effects on either the aboveground or the belowground community. Our results emphasize the importance of directly addressing the soil microbial community as a factor that influences aboveground food web structure by affecting plant size and aboveground plant nitrogen.
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Affiliation(s)
- Jes Hines
- Department of Entomology, University of Maryland, College Park 20742, USA.
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Mooney KA, Linhart YB. Contrasting cascades: insectivorous birds increase pine but not parasitic mistletoe growth. J Anim Ecol 2006; 75:350-7. [PMID: 16637988 DOI: 10.1111/j.1365-2656.2006.01054.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Intraguild predation occurs when top predators feed upon both intermediate predators and herbivores. Intraguild predators may thus have little net impact on herbivore abundance. Variation among communities in the strength of trophic cascades (the indirect effects of predators on plants) may be due to differing frequencies of intraguild predation. Less is known about the influence of variation within communities in predator-predator interactions upon trophic cascade strength. 2. We compared the effects of a single predator community between two sympatric plants and two herbivore guilds. We excluded insectivorous birds with cages from ponderosa pine Pinus ponderosa trees parasitized by dwarf mistletoe Arceuthobium vaginatum. For 3 years we monitored caged and control trees for predatory arthropods that moved between the two plants, foliage-feeding caterpillars and sap-feeding hemipterans that were host-specific, and plant damage and growth. 3. Excluding birds increased the abundance of ant-tended aphids on pine and resulted in an 11% reduction in pine woody growth. Mutualist ants protected pine-feeding aphids from predatory arthropods, allowing aphid populations to burgeon in cages even though predatory arthropods also increased in cages. By protecting pine-feeding aphids from predatory arthropods but not birds, mutualist ants created a three-tiered linear food chain where bird effects cascaded to pine growth via aphids. 4. In contrast to the results for tended aphids on pine, bird exclusion had no net effects on untended pine herbivores, the proportion of pine foliage damaged by pine-feeding caterpillars, or the proportion of mistletoe plants damaged by mistletoe-feeding caterpillars. These results suggest that arthropod predators, which were more abundant in cages as compared with control trees, compensated for bird predation of untended pine and mistletoe herbivores. 5. These contrasting effects of bird exclusion support food web theory: where birds were connected to pine by a linear food chain, a trophic cascade occurred. Where birds fed as intraguild predators, the reticulate food webs linking birds to pine and mistletoe resulted in no net effects on herbivores or plant biomass. Our study shows that this variation in food web structure occurred between sympatric plants and within plants between differing herbivore guilds.
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Affiliation(s)
- Kailen A Mooney
- University of Colorado, Department Ecology and Evolutionary Biology, Boulder, CO 80309-0334, USA.
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Cornelissen T, Stiling P. Responses of different herbivore guilds to nutrient addition and natural enemy exclusion. ECOSCIENCE 2006. [DOI: 10.2980/1195-6860(2006)13[66:rodhgt]2.0.co;2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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