Predation alters community structure through multiple trophic cascades
Data files
May 02, 2025 version files 56.69 KB
Abstract
Predation plays a crucial role in shaping community structure and can initiate trophic cascades that alter abundances across adjacent trophic levels. Intraspecific variation among predators could lead to varying levels of top-down control with implications for trophic cascade strength. In this experiment, we manipulated body size variation in populations of predatory mole salamanders (Ambystoma talpoideum) within mesocosms and monitored a suite of abiotic and biotic responses. Measurements of these responses are contained within this dataset. We predicted that predator populations with increased body size variation would have limited top-down control due to weaker interactions with greater numbers of prey species. Conversely, we predicted that populations with similarly sized predators would have strong control over fewer prey species, leading to trophic cascades. Salamander presence affected nearly every parameter measured, suppressing some populations (e.g., invertebrate predators) and facilitating others (e.g., invertebrate collectors), triggering multiple trophic cascades across several trophic channels, including both “green” and “brown” pathways. However, only a few invertebrate taxa responded to variation in predator body size, and in nearly all these instances, those taxa responded more strongly to treatments with increased body size variation than to treatments with similarly sized predators. In contrast to our hypothesis, predator size variation may promote individual dietary specialization of differently sized predators, resulting in strong control of focal prey. These results demonstrate that predators can have pervasive and multichannel effects on all trophic levels within communities, regardless of size structure, and that increased body size variation can lead to stronger top-down control.
Dataset DOI: 10.5061/dryad.6q573n68k
Description of the data and file structure
This study examined how predator body size variation shapes aquatic community structure. We conducted mesocosm experiments with size-structured predatory mole salamanders and collected a suite of abiotic and biotic parameters, which are provided here. The primary dataset presents data collected at periodic sampling bouts, while the secondary dataset presents tadpole abundance data collected at times other than these core sampling bouts. Results of the mesocosm experiment revealed dual trophic cascades triggered by mole salamanders, highlighting the pervasive, multi-channel influence of predators across all trophic levels in pond communities.
Files and variables
File: PredationAltersCommunityStructure2024_Data.csv
Description: Data collected in each mesocosm during the study period of April - September 2016. Mesocosms were constructed in 1000L cattle tanks and spatially divided into six blocks with two replicates of each treatment (High size variation, Low size variation, or Control) per block for a total of 36 mesocosms. Collected data include water quality parameters, tadpole abundances, decomposition (ash-free dry mass), chlorophyll-a concentrations (in periphyton and phytoplankton), zooplankton, invertebrate communities (in the benthos and in leaf packs), and surface coverage of bladderwort & algae mats.
Any columns prefixed with ‘LP_’ indicate data collected from leaf packs placed at the beginning of the experiment, and any columns prefixed with ‘Benthos’ indicate data collected from grab-sampling of the benthic leaf litter. As described in the Methods of the associated article, invertebrates were assigned to one of four functional feeding groups, and invertebrate taxa biomasses were calculated using length-mass regressions. Abundances and biomasses of certain specific taxa are detailed at the end of the spreadsheet, otherwise, all invertebrate data are reported to the functional feeding group level.
Leaf packs (invertebrates and ash-free dry mass) and periphyton data were not collected in April at the initiation of the experiment. Tadpole data was not collected until the end of May and is first reported in June in this dataset. One Benthic sample was lost, from the May sampling bout in tank 33. Due to user error, no water quality parameters were taken in the April sample for tank 21. Due to an equipment error, turbidity was not measured in the June sample for tank 34. Any data that was not collected, either intentionally or through error, is noted with ‘NA’.
Variables
- Tank: The unique identifier for each individual mesocosm tank. The identifier is made up of the block number + the treatment number.
- Block: One of six spatially arranged blocks to compensate for environmental variability across the mesocosm array. Each block has six mesocosm tanks.
- Treatment: A numerical code for the SizeClass treatment, which was replicated twice per block. High variation = 1, 3; Low variation = 4, 6; Control =2, 5.
- SizeClass: Experimental manipulation of body size variation in populations of salamanders. Treatments include high body size variation ('High'), low body size variation ('Low'), or the absence of salamanders ('Control').
- Date: The month in which the observations were collected. All observations were collected once per indicated month in 2016 (approximately 1, 5, 8, 13, and 21 weeks post-addition of salamanders on April 14, 2016).
- Temperature: Temperature in degrees Celsius of the mesocosm water, as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- pH: pH of the mesocosm water, as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- DO: Dissolved Oxygen concentration in mg/L of the mesocosm water as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- Turbidity: Turbidity in Nephelometric Turbidity Units (NTU, higher values indicate higher turbidity) of the mesocosm water as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- ORP: Oxidation-Reduction Potential in millivolts (mV) of the mesocosm water as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- Conductivity: Conductivity of the mesocosm water as measured with a multi-sensor sonde (Yellow Springs Incorporated, model 6820).
- SRP: Soluble Reactive Phosphorus concentrations in mg/L in the mesocosm water.
- Nitrates: Nitrate concentrations in mg/L in the mesocosm water.
- AFDM: Ash-Free Dry Mass of leaves from the leaf packs. Data are presented in grams and are a measure of decomposition.
- Periphyton: Concentrations of Chlorophyll-a (mg/m3) in algal periphyton collected from stone tiles within the mesocosm.
- Phytoplankton: Concentrations of Chlorophyll-a (mg per cubic meter) in pelagic phytoplankton collected from mesocosm water.
- ZoopTotal: Total number of zooplankton per 5mL of mesocosm water.
- Cladocera: Total number of cladoceran zooplankton per 5mL of mesocosm water.
- Rotifera: Total number of rotifer zooplankton per 5mL of mesocosm water.
- Cyclopoid: Total number of cyclopoid copepods per 5mL of mesocosm water.
- Nauplii: Total number of nauplii per 5mL of mesocososm water.
- TadpoleAbund: Counts of tadpoles within mesocosms, as visually counted in a fixed 30x40cm quadrat. Tadpole observations were aggregated to conform to the dates of the main sampling bouts.
- LP_GrandTotal: Total counts of invertebrates in the leaf packs, including ostracoda (i.e., invertebrate filterers).
- LP_TotalNoOstra: Total counts of invertebrates in the leaf packs, excluding ostracoda (i.e,. invertebrate filterers).
- LP_Predator: Counts of invertebrate predators in the leaf packs.
- LP_Collector: Counts of invertebrate collectors in the leaf packs.
- LP_Grazer_NoAncyl: Counts of invertebrate grazers, excluding Ancyclidae, in the leaf packs.
- LP_Grazer_wAncycl: Counts of invertebrate grazers, including Ancyclidae, in the leaf packs.
- LP_Filterer: Counts of invertebrate filterers in the leaf packs. Filterers were 100% represented by Ostracoda.
- Benth_Total: Total count of invertebrates in the benthic samples.
- Benth_Predator: Counts of invertebrate predators in the benthic samples.
- Benth_Collector: Counts of invertebrate collectors in the benthic samples.
- Benth_Grazer: Counts of invertebrate grazers in the benthic samples.
- Benth_Filterer: Counts of invertebrate filterers in the benthic samples.
- LP_Biomass_Total: Total biomass (mg) of invertebrates in the leaf packs, including ostracoda.
- LP_Biomass_Total_NoOstra: Total biomass (mg) of invertebrates in the leaf packs, excluding ostracoda.
- LP_Biomass_Predator: Biomasses (mg) of invertebrate predators in the leaf packs.
- LP_Biomass_Collector: Biomasses (mg) of invertebrate collectors in the leaf packs.
- LP_Biomass_Grazer: Biomasses (mg) of invertebrate grazers in the leaf packs.
- LP_Biomass_Filterer: Biomasses (mg) of invertebrate filterers (100% represented by ostracoda) in the leaf packs.
- Benth_Biomass_Total: Total biomass (mg) of invertebrates in the benthic samples.
- Benth_Biomass_Predator: Biomasses (mg) of invertebrate predators in the benthic samples.
- Benth_Biomass_Collector: Biomasses (mg) of invertebrate collectors in the benthic samples.
- Benth_Biomass_Grazer: Biomasses (mg) of invertebrate grazers in the benthic samples.
- SurfaceCoverage_Total: Surface coverage (m^2) of floating vegetative mats in the mesocosm tanks.
- SurfaceCoverage_Utric: Surface coverage (m^2) of just the Utricularia (bladderwort) component of floating vegetative mats in the mesocosm tanks.
- SurfaceCoverage_Alg: Surface coverage (m^2) of just the algal component of floating vegetative mats in the mesocosm tanks.
- LP_Hydrophilidae: Counts of Hydrophilid larvae in the leaf packs.
- LP_Chiro: Counts of Chironomidae in the leaf packs.
- LP_Physidae: Counts of Physid snails in the leaf packs.
- LP_Ancycl: Counts of Ancyclidae in the leaf packs.
- Benthos_Hydro: Counts of Hydrophilid larvae in the benthic samples.
- Benth_Chiro: Counts of Chironomidae in the leaf packs.
File: PredationAltersCommunityStructure2024_DataTadpoles.csv
Description: Counts of tadpoles within mesocosms, as visually measured in a fixed 30x40cm quadrat ('Count') and extrapolated to abundances per cubic meter of water (CountPerM3). If no tadpoles were observed, a value of 0 is recorded.
Variables
- SizeClass: Experimental manipulation of body size variation in populations of salamanders. Treatments include high body size variation ('High'), low body size variation ('Low'), or the absence of salamanders ('Control').
- Block: One of six spatially arranged blocks to compensate for environmental variability across the mesocosm array.
- Treatment: A numerical code for the Size Class, which was replicated twice per block. High = 1, 3; Low = 4, 6; Control =2, 5.
- Date: The observation date, all observations were conducted in 2016.
- Count: Counts of tadpoles within mesocosms, as visually counted in a fixed 30x40cm quadrat
- CountPerM3: Counts of tadpoles extrapolated to a cubic meter of water.
Code/software
Any basic spreadsheet viewer will work with this data. The data are saved in Comma Separated Values (.csv) format, which is compatible with a wide range of software.
Access information
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