Dataset DOI: 10.5061/dryad.0rxwdbsd8

Description of the data and file structure

Supplementary data files for: What is regulating chironomid populations? The influence of food supply and interference competition on development and mortality in Chironomus riparius.

This compilation includes experimental raw data as well as R scripts and input data for calculating EmT₅₀ values (the time until emergence of 50% of the surviving larvae) and for the statistical analysis of several observational endpoints regarding food availability and larval density.

Experimental design of the study: First instar larvae < 12h of Chironomus riparius were added to glass beakers of different sizes (50, 180, and 600 cm²) containing Elendt M4 medium and artificial sediment (OECD guideline 219). The tests were conducted in the laboratory at 20°C without water exchange up to 62 days. Larval densities ranging from 10 to 200 per beaker and daily feed additions ranging from 0.05 to 0.5 mg dw larva⁻¹ and day⁻¹ were investigated. TetraPhyll was used as food for the larvae. Four replicates were prepared for all density-food combinations (further details can be found in Strauss et al. 2025).

Files and variables

File: Experimental_rawdata.zip

The experimental data is available as CSV files (semicolon- and tab-separated) and can be displayed using e.g., Microsoft Excel.

Description: This folder provides the following experimental raw data and calculations: emergence data over time; calculated time to 50% emergence (EmT₅₀); surviving larvae and emerged individuals as well as calculated mortality at the end of the test; calculated relative emerging success; numbers of eggs per egg rope; oxygen and pH measurements; dry weight measurements of surviving larvae at the end of the test; criteria for outliers in emergence data. 

Column headings for the test design, applicable to all CSV files containing experimental data:

·       Food level (mg dw larva⁻¹ day⁻¹): Daily food amount per larva expressed in mg dw TetraPhyll

·       Initial density larvae (#): Total number of larvae per beaker at the start of the experiment (day 0)

·       Area (cm²): Sediment area of the respective beakers

·       Density (larvae / 50 cm²): Initial density of larvae, converted to individuals per 50 cm² for all beaker sizes

·       Additional information is provided on the replicate number, the date of sampling, and the respective experimental day.

Overview of the CSV-files with their names and contents:

·       Raw data emergence.csv

Description: Number of emerged adults per day and replicate. Please note: 5 replicates were classified as outliers and excluded from further analysis. For the criteria, see the data file „Criteria for outliers.csv“.

Reported results: Emerged males (daily number), Emerged females (daily number), Sum of emerged adults (daily number), Cumulative emerged adults, Cumulative emerged males, Cumulative emerged females, % cumulative total emergence per initial number of larvae.

·      Development replicates.csv

Description: Results of fitting a two-parameter log-logistic model to the cumulative emergence data over time for individual replicates. The development speed EmT₅₀ is expressed in days until emerging of 50 % of the surviving larvae. Please note: 5 replicates were classified as outliers and excluded from further analysis. For the criteria, see the corresponding spreadsheet.

Reported results: EmT₅₀ (d): Days to 50 % emergence; slope b: Slope of the two-parameter log-logistic model; R²: coefficient of determination of the two-parameter log-logistic model.

·       Development.csv

Description: The development speed EmT₅₀ expressed in days until emerging of 50 % of the surviving larvae, mean values, and standard deviation (M ± SD) of replicates.

Reported results: EmT₅₀ (d) - mean values of replicates; EmT₅₀ (d) - SD of replicates; Number of replicates (n): Number of replicates evaluated without outliers.

·      Rawdata at Test End.csv

Description: Overview of the results regarding the combinations of larval density and food supply after completion of the experiments for each individual replicate.

Reported results: Vital larvae (#); Vital pupae (#); Total emergence (#); Calculated mortality (#); Mortality (%): mortality based on initial larvae number; Comments on mortality (%).

·       Mortality.csv

Description: Mortality (% of initial larvae) at the test end (M ± SD).

Reported results: Total daily food (mg dw beaker⁻¹ d⁻¹); Dead animals at test end (#/beaker); Daily mortality rate (% / d) - mean values of replicates; Daily mortality rate (% / d) - SD of replicates; Mortality at test end (%) - mean value of replicates; Mortality at test end (%) – SD of replicates; Number of replicates (n): Number of replicates evaluated without outliers.

·       Emergence success.csv

Description: Emergence success (% emerged adults per initial number of larvae) at the test end (M ± SD).

Reported results: % Emergence success - mean values of replicates; % Emergence success - SD of replicates; Number of replicates (n): Number of replicates evaluated without outliers.

·       Reproduction.csv

Description: Egg number per rope oviposited by female midges (M ± SD).

Reported results: Food level (mg dw larva⁻¹ d⁻¹); Density (larvae / 50 cm²); Eggs per rope - Mean values of evaluated egg clutches; Eggs per rope – SD of evaluated egg clutches; Number of clutches (n): Number of egg clutches evaluated.

·       Oxygen and pH values.csv

Description: Oxygen and pH measurements in the experimental beakers

Reported results: Total daily food (mg dw beaker⁻¹ d⁻¹); pH-value (-); Oxygen (mg O₂/L); Oxygen saturation (%).

·       Larval dry weight.csv

Description: Dry weight measurements of surviving larvae at the end of the experiments.

Reported results: Number of vital larvae (#); Dry weight of pooled larvae (mg); mean dry weight per individual (mg/larva).

·       Criteria for outliers.csv

Description: Criteria for data outliers in emergence data, specifying the replicas affected

File: Figures_Development_replicates.zip

Description: This folder contains all figures (as PNG files) of the cumulative emergence of adults based on the data in the file „Development replicates.csv“ and the fitted regression curves, each for every replicate evaluated.

The PNG files are named as: Figure number _ X Food level … larval density … replicate number.

File: R-Calculation_of_EmT50_values.zip

Description: Folder contents: Data and scripts for calculating EmT₅₀ values from emergence data for all combinations of food and density using a two-parameter log-logistic model.

Comment: The results for all replicates can be found in the files ‘Development_replicates.csv’ and graphically in the zip folder ‘Figures_Development_replicates.zip’.

File names and contents:

·       Legend_EmT50_calculation.txt: Legend for the R input data file

·       food_dep_emerg_data.csv: R input data for EmT₅₀ calculations

·       food_dep_emerg_drc_analyses.r: R script for EmT₅₀ calculations

·       food_dep_emerg_data.docx: R script for EmT₅₀ calculations as a word file

File: R-Statistical_analysis.zip

Description: Folder contents: Data and scripts for statistical analysis of mortality, development, and reproduction data with regard to food and density dependency.

File names and contents:

·       Legend_statistics.txt: Legend for all R input data files for statistical analysis

·       Mortality.csv: R input data for mortality statistics

·       mortality_food_density.r: R script for mortality statistics

·       Mortality vs food and density.docx: R script for mortality statistics as a Word file

·       EmT50.csv: R input data for EmT₅₀ statistics

·       analyse_EmT50.r: R script for EmT₅₀ statistics

·       EmT₅₀ vs food and density.docx: R script for EmT₅₀ statistics as a Word file

·       Egg_number.csv: R input data for reproduction statistics

·       analyse_egg_numbers.r: R script for reproduction statistics

·       Egg numbers vs food and density.docx: R script for reproduction statistics as a Word file

Code/software

R packages used for statistical analysis:

All statistical analyses were performed using R 4.3.2 (R Core Team 2023).

Calculation of EmT₅₀ values from emergence data: The sigmoidal cumulative emergence curves over time adjusted for mortality could be well described with a two-parameter log-logistic model based on the Hill equation. Regression equation: y = 1 / (1 + (x₀/x)^b, with: x₀: time of 50 % emergence (EmT₅₀) (d); b: the slope of the cumulative emergence curve; y: fraction of emerged individuals as a function of the experimental time x (d).

This model was fitted to each cumulative emergence curve, individually, to determine the time to 50% emergence success (EmT₅₀) for each replicate. The model was fitted using the function ‚drm‘ (settings: fct=LL.2(), type="binomial") from package ‚drc‘ (Ritz et al. 2015) in R (R Core Team 2023), and was then used to interpolate the median time to emergence (EmT₅₀) for each respective curve.

Mortality: Since mortality is a binominal variable, we used a generalized linear model (GLM) with beta distribution to describe the mortality rate and mortality at the end of the tests (ratio of dead to initial number of larvae) as a function of food per larva and larval density using the function ‚betareg´ from the R package betareg (Vers. 3.1.4, Cribari-Neto and Zeileis 2010).

Reproduction: The egg number per clutch was assumed to be Poisson distributed (discrete, (0,+inf)). Data were tested for overdispersion (function ‚dispersiontest´ from R package AER, Cameron and Trevedi 1990), and two alternative GLM models (Poisson and quasi-Poisson, fitted with function ‚glm´ (McCullagh and Nelder 1989)).