DOI: 10.5061/dryad.wdbrv161p
title: Effects of competition and predation risk from a life history intraguild predator on individual specialisation

description: 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.
description: # Effects of competition and predation risk from a life history intraguild
 predator on individual specialisation Dataset DOI:
 [10.5061/dryad.wdbrv161p](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