Effects of competition and predation risk from a life history intraguild predator on individual specialisation
Data files
Jul 24, 2025 version files 410.57 KB
-
Diet_script.R
12.59 KB
-
Habitat_data.csv
336.83 KB
-
Habitat_script.R
12 KB
-
PreyData.csv
45.55 KB
-
README.md
3.60 KB
Abstract
Individuals can deploy a variety of ecological and behavioural strategies to obtain resources, often using only a subset of the total resource diversity used by their population. This phenomenon of individual specialisation (IS) is nearly ubiquitous across taxa, and has the potential to affect population dynamics and ecosystem processes. Pairwise antagonistic interactions such as competition and predation can influence the degree of IS in a population, but little is known about the combined effects of multiple simultaneous interaction types between species, including intraguild predation (competition and predation from a single antagonist).
We address this gap by asking how the combination of competition and predation risk from an invasive intraguild predator – Eurasian perch Perca fluviatilis – impacts the degree of dietary and habitat IS in a native New Zealand fish, the common bully Gobiomorphus cotidianus. Bullies exhibit a generalised diet at the population level and compete for benthic and pelagic prey with juvenile perch, while also being subject to predation by larger perch.
We used a mesocosm experiment to explore how competition from young-of-year perch and perceived predation risk from sub-adult perch influence IS within bully populations. Over a 3-month period, we monitored individual habitat use and used serial gastric lavage to sample time-integrated individual diets.
We found that the presence of juvenile perch was associated with a decrease in dietary IS associated with a shift to more benthic feeding, while habitat IS was affected by an antagonistic interaction between competition and predation whereby presence of small perch negated a negative effect of large perch on IS.
This study demonstrates the importance of considering multiple interaction types when evaluating how interspecific interactions influence individual variation within populations.
Dataset DOI: 10.5061/dryad.wdbrv161p
Description of the data and file structure
Data from mesocosm study on effects of small perch (competitor) and large perch (predation risk) on individual common bully diet and habitat use. Diet and habitat are stored in separate spreadsheets, each with a detailed R script that walks through all analyses used in the manuscript.
Files and variables
File: Diet_script.R
Description: Script for running all diet analyses, including making figures
File: Habitat_script.R
Description: Script for running all habitat analyses, including making figures
File: PreyData.csv
Description: Stomach content data for analysis
Variables
- Date (DD/MM/YY)
- Time (24:00)
- Session - 1-5 temporal sessions for stomach content sampling using gastric lavage
- Keep - index used to exclude some observations (see manuscript for criteria)
- Tank - mesocosm identifier
- Treatment - four treatments crossing Pred (predator presence) with Comp (competitor presence)
- Large perch present - presence of predator (yes/no)
- Small perch present - presence of competitor (yes/no)
- Fish - species of fish (common bully or perch)
- FishID - fish identifier based on elastomer tags
- Ceri. - number of Ceriodaphnia
- Chyd. - number of Chydorids
- Cycl. - number of Cyclopoid copepods
- Ostr. - number of Ostracods
- Chir.Larv. - number of Chironominae larvae
- Tany. - number of Tanypodinae larvae
- Potam. - number of Potamopyrgus snails
- Physa - number of Physa snails
- Mite - number of mites
- Planorb. - number of Planorbid snails
- Di.Pup - number of Diptera pupae
- Cerat. - number of Ceratopogonid larvae
- Sigara - number of Sigara water boatmen
- Odon. - number of Odonate larvae
- Trichopt. - number of Trichoptera larvae
- TOTAL_PREY_ITEMS - combined number of prey items across categories
File: Habitat_data.csv
Description:
Variables
- Tank - mesocosm identifier
- Treatment - four treatments crossing Pred (predator presence) with Comp (competitor presence)
- Large_perch_present - presence of predator (yes/no)
- Small_perch_present - presence of competitor (yes/no)
- Fish - species of fish (common bully or perch)
- Date - full date and time (DD/MM/YY 12:00 AM/PM)
- Day (DD/MM/YY)
- Time (12:00 AM/PM)
- FishID - fish identifier based on elastomer tags
- ACTIVITY - behaviour category (see text)
- HABITAT - microhabitat category (see text)
- DIST to SHELTER - distance to nearest shelter (cm - not used)
- DIST to BOTTOM - distance to bottom of tank (cm - not used)
- Bef/Aft Obs seen - notes on whether observer appeared to be noticed during observation
- COMMENTS - other comments
- Seen - note on whether bully seen during observation bout (1 = yes, 0 = no)
- Present - note on whether bully was later inferred to still be present (whether seen or not)
- Keep (observation) - filter to retain the observation (1 = yes, 0 = no)
- Keep (Analysis) - filter to retain the observation for data analysis (see manuscript for criteria) (1 = yes, 0 = no)
Code/software
R (version 4.4.1) with scripts provided to replicate all analyses presented in manuscript.
R extension packages:
readr, plyr, dplyr, reshape2, RInSp, vegan, lme4, car, heplots, emmeans, ggplot2, rcartocolor, gridExtra
Access information
Other publicly accessible locations of the data:
- N/A
Data was derived from the following sources:
- Mesocosm experiment