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Multiple-Predator Effects and Functional Redundancy of Pond Predators. J HERPETOL 2022. [DOI: 10.1670/20-080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Direct effects influence larval salamander size and density more than indirect effects. Oecologia 2021; 195:173-186. [PMID: 33387008 DOI: 10.1007/s00442-020-04820-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 12/04/2020] [Indexed: 10/22/2022]
Abstract
Direct and indirect effects both influence population and community dynamics. The relative strengths of these pathways are often compared using experimental approaches, but their evaluation in situ has been less frequent. We examined how individual and aggregate impacts of direct and indirect effects of species densities, proxies for competition and predation pressure, and habitat variables influenced patterns of larval density and body size of ringed (Ambystoma annulatum) and spotted salamanders (A. maculatum). We surveyed > 150 ponds in Missouri, USA, from 2012 to 2014 to measure the density and body size of each focal species, the density of co-occurring pond food web members, and select habitat features. We used structural equation modeling to quantify the relative importance of direct and indirect pathways on both body size and larval density. Overall, both responses were explained through a combination of direct and indirect effects. However, the magnitudes of direct effects were often greater than indirect effects. Some of the direct and indirect relationships with larval salamander size and density were also consistent with results from experimental studies. Finally, total direct and indirect effects were often weaker due to habitat and density variables negating each other's impacts. Overall, our study shows that direct effects were equivalent to, or more important than, indirect effects. We also demonstrate that the effects stemming from individual relationships can sum to produce net patterns that are negligible in magnitude. Further work on direct and indirect effects with observational data are needed to examine their magnitudes in natural communities.
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Cayuela H, Griffiths RA, Zakaria N, Arntzen JW, Priol P, Léna JP, Besnard A, Joly P. Drivers of amphibian population dynamics and asynchrony at local and regional scales. J Anim Ecol 2020; 89:1350-1364. [PMID: 32173904 DOI: 10.1111/1365-2656.13208] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 01/13/2020] [Indexed: 02/06/2023]
Abstract
Identifying the drivers of population fluctuations in spatially distinct populations remains a significant challenge for ecologists. Whereas regional climatic factors may generate population synchrony (i.e. the Moran effect), local factors including the level of density dependence may reduce the level of synchrony. Although divergences in the scaling of population synchrony and spatial environmental variation have been observed, the regulatory factors that underlie such mismatches are poorly understood. Few previous studies have investigated how density-dependent processes and population-specific responses to weather variation influence spatial synchrony at both local and regional scales. We addressed this issue in a pond-breeding amphibian, the great crested newt Triturus cristatus. We used capture-recapture data collected through long-term surveys in five T. cristatus populations in Western Europe. In all populations-and subpopulations within metapopulations-population size, annual survival and recruitment fluctuated over time. Likewise, there was considerable variation in these demographic rates between populations and within metapopulations. These fluctuations and variations appear to be context-dependent and more related to site-specific characteristics than local or regional climatic drivers. We found a low level of demographic synchrony at both local and regional levels. Weather has weak and spatially variable effects on survival, recruitment and population growth rate. In contrast, density dependence was a common phenomenon (at least for population growth) in almost all populations and subpopulations. Our findings support the idea that the Moran effect is low in species where the population dynamics more closely depends on local factors (e.g. population density and habitat characteristics) than on large-scale environmental fluctuation (e.g. regional climatic variation). Such responses may have far-reaching consequences for the long-term viability of spatially structured populations and their ability to respond to large-scale climatic anomalies.
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Affiliation(s)
- Hugo Cayuela
- Institut de Biologie Integrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Richard A Griffiths
- Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, UK
| | - Nurul Zakaria
- Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, UK
| | - Jan W Arntzen
- Naturalis Biodiversity Center, Leiden, The Netherlands
| | | | - Jean-Paul Léna
- UMR 5023 LEHNA, Université de Lyon, Lyon1, CNRS, ENTPE, Villeurbanne, France
| | - Aurélien Besnard
- CNRS, PSL Research University, EPHE, UM, SupAgro, IRD, INRA, UMR 5175 CEFE, Montpellier, France
| | - Pierre Joly
- UMR 5023 LEHNA, Université de Lyon, Lyon1, CNRS, ENTPE, Villeurbanne, France
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Anderson TL, Stemp KM, Ousterhout BH, Burton D, Davenport JM. Impacts of phenological variability in a predatory larval salamander on pond food webs. J Zool (1987) 2019. [DOI: 10.1111/jzo.12733] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- T. L. Anderson
- Department of Biology Southeast Missouri State University Cape Girardeau MO USA
- Department of Biology Appalachian State University Boone NC USA
| | - K. M. Stemp
- Department of Biology Southeast Missouri State University Cape Girardeau MO USA
- Department of Biology Appalachian State University Boone NC USA
| | - B. H. Ousterhout
- National Great Rivers Research and Education Center East Alton IL USA
| | - D. Burton
- Department of Biology Appalachian State University Boone NC USA
| | - J. M. Davenport
- Department of Biology Southeast Missouri State University Cape Girardeau MO USA
- Department of Biology Appalachian State University Boone NC USA
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Ousterhout BH, Semlitsch RD. Effects of conditionally expressed phenotypes and environment on amphibian dispersal in nature. OIKOS 2018. [DOI: 10.1111/oik.05276] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Brittany H. Ousterhout
- Division of Biological Sciences; Univ. of Missouri; Columbia MO USA
- Dept of Biological Sciences; Univ. of Arkansas; Fayetteville AR 72701 USA
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Anderson TL, Rowland FE, Semlitsch RD. Variation in phenology and density differentially affects predator-prey interactions between salamanders. Oecologia 2017; 185:475-486. [PMID: 28894959 DOI: 10.1007/s00442-017-3954-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 09/02/2017] [Indexed: 11/26/2022]
Abstract
Variation in the timing of breeding (i.e., phenological variation) can affect species interactions and community structure, in part by shifting body size differences between species. Body size differences can be further altered by density-dependent competition, though synergistic effects of density and phenology on species interactions are rarely evaluated. We tested how field-realistic variation in phenology and density affected ringed salamander (Ambystoma annulatum) predation on spotted salamanders (Ambystoma maculatum), and whether these altered salamander dynamics resulted in trophic cascades. In outdoor mesocosms, we experimentally manipulated ringed salamander density (low/high) and breeding phenology (early/late) of both species. Ringed salamander body size at metamorphosis, development, and growth were reduced at higher densities, while delayed phenology increased hatchling size and larval development, but reduced relative growth rates. Survival of ringed salamanders was affected by the interactive effects of phenology and density. In contrast, spotted salamander growth, size at metamorphosis, and survival, as well as the biomass of lower trophic levels, were negatively affected primarily by ringed salamander density. In an additional mesocosm experiment, we isolated whether ringed salamanders could deplete shared resources prior to their interactions with spotted salamanders, but instead found direct interactions (e.g., predation) were the more likely mechanism by which ringed salamanders limited spotted salamanders. Overall, our results indicate the effects of phenological variability on fitness-related traits can be modified or superseded by differences in density dependence. Identifying such context dependencies will lead to greater insight into when phenological variation will likely alter species interactions.
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Affiliation(s)
- Thomas L Anderson
- Division of Biological Sciences, University of Missouri, 105 Tucker Hall, Columbia, MO, 65211, USA.
- Department of Ecology and Evolutionary Biology, University of Kansas, 2101 Constant Ave, Lawrence, KS, 66047, USA.
| | - Freya E Rowland
- Division of Biological Sciences, University of Missouri, 105 Tucker Hall, Columbia, MO, 65211, USA
| | - Raymond D Semlitsch
- Division of Biological Sciences, University of Missouri, 105 Tucker Hall, Columbia, MO, 65211, USA
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Moving beyond the plane: measuring 3D home ranges of juvenile salamanders with passive integrated transponder (PIT) tags. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2284-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Rowland FE, Rawlings MB, Semlitsch RD. Joint effects of resources and amphibians on pond ecosystems. Oecologia 2016; 183:237-247. [PMID: 27718066 DOI: 10.1007/s00442-016-3748-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 09/29/2016] [Indexed: 11/28/2022]
Abstract
Primary production can be controlled through bottom-up (e.g., resources) or top-down (e.g., predators) constraints. Two key bottom-up resources in small aquatic systems are light and nutrients, and forest canopy cover heavily influences these factors, whereas amphibian and invertebrate colonizers exert top-down pressure as grazers and predators. We designed our experiment to specifically manipulate two different top-down and bottom-up factors. We manipulated resources by altering light (low/high) and nutrient (low/high) availability; omnivores with the presence/absence of southern leopard frog tadpoles (Lithobates sphenocephalus); and predators with the presence/absence of spotted salamander larvae (Ambystoma maculatum) in a full-factorial experiment conducted over 14 weeks. We observed that both bottom-up and top-down effects were important in predicting lower trophic level biomass. We found a significant top-down effect of salamanders on Daphnia, but tadpoles had the strongest overall effect on the food web, influencing phytoplankton (+), periphyton (-), and chironomids (-). None of our models were good predictors of phytoplankton biomass, but both shading and nutrient availability relatively equally boosted periphyton biomass. We also found large temporal differences in food-web dynamics. Our results underscore the need for more information into how ecosystem functioning could be altered by land use, amphibian extirpation, and climate change.
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Affiliation(s)
- Freya E Rowland
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA.
| | - Madelyn B Rawlings
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Raymond D Semlitsch
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
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Agonistic Behavior and Resource Defense among Sympatric Juvenile Pond-Breeding Salamanders. J HERPETOL 2016. [DOI: 10.1670/15-160] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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