DOI: 10.5061/dryad.2280gb657
title: Reduced intraspecific variation in lake trout food webs under warmer temperatures and smaller ecosystem sizes: data and code

description: Food web theory has illustrated that mobile top predators, such as lake
 trout (Salvelinus namaycush), can be potent stabilizers of food webs due
 to their ability to shift foraging behaviours in response to changing
 conditions. Consistent with this, research has demonstrated that mean lake
 trout food web attributes (i.e., trophic position and nearshore coupling)
 structurally change across environmental gradients; however, intraspecific
 variation in these attributes across gradients has not been fully
 explored. Here, we used stable isotope-based food web metrics to
 investigate how both mean and intraspecific variation in trophic structure
 changes in Canadian boreal shield lakes across gradients in ecosystem
 size, temperature and competition. Consistent with earlier findings, we
 find nearshore coupling decreases and trophic position increases with
 warmer summer climate. In contrast to previous findings, increasing lake
 area predicted increased nearshore coupling and was not associated with
 lake trout trophic position.  Our results show that warmer
 temperatures and smaller ecosystem sizes reduce the expression of
 intraspecific variation in food web structures. Specifically, larger lakes
 increased variation in nearshore coupling and trophic position resulting
 in larger niche areas, and warmer lakes reduced variation in nearshore
 coupling and tended to generate smaller niche areas. Interestingly, we
 found little evidence for the relative abundance of lake trout or other
 predator taxa (surrogates of intra and interspecific competition)
 influencing mean and variance in lake trout trophic structure.
 Intraspecific variation can promote ecosystem resilience by enabling
 diverse individual responses that help buffer populations against
 environmental change. Therefore, reduction in intraspecific variation in
 smaller, warmer lakes may have undesirable consequences for lake trout and
 the biota in these Canadian boreal shield lakes, leaving these ecosystems
 less able to adjust to future perturbations.
description: # Reduced intraspecific variation in lake trout food webs under warmer
 temperatures and smaller ecosystem sizes: data and code Dataset DOI:
 [10.5061/dryad.2280gb657](10.5061/dryad.2280gb657) ## Description of the
 data and file structure Data and code for intraspecific variation
 manuscript. Data contains stable isotope and lake attribute data from 52
 lakes in Ontario, Canada.  ### Files and variables #### File:
 bsm_analysis_datJuly2025.csv **Description:** Data that includes SIBER
 metrics, lake morphometrics and competition variables used for the main
 analysis. ##### Variables * Lake_Name: lake name * SEAc: standard ellipse
 area (small sample size corrected) * dY_range: trophic position range *
 dX_range: proportion of nearshore carbon range * TA: total area (isotopic
 niche area) * CD: centroid distance (isotopic) * NND: nearest neighbour
 distance (isotopic) * SDNND: standard deviation of nearest neighbour
 distance (isotopic) * sampling_year: year the lake was sampled * Area_ha:
 lake area in hectares * Secchi_depth: secchi depth in metres *
 summer_air_temp: mean summer air temperature in degrees celsius  *
 LaTro_CUE: lake trout catch per unit effort * NoPik_CUE: northern
 pike catch per unit effort * Burbo_CUE: burbot catch per unit effort *
 Walle_CUE: walleye catch per unit effort * LmBas_CUE: largemouth
 bass catch per unit effort * Muske_CUE: muskellunge catch per unit effort
 * total_pred_CUE: total predator catch per unit effort * log_area_ha:
 natural log of lake area (metres) * log_dY_range: natural log of trophic
 position range * log_dX_range: natural log of proportion of nearshore
 carbon range * log_SEAc: natural log of standard ellipse area (small
 sample size corrected) * log_LaTro_CUE: natural log of lake trout catch
 per unit effort * log_NND: natural log of nearest neighbour distance  *
 log_SDNND: natural log of standard deviation of nearest neighbour
 distance  * log_CD: natural log of centroid distance *
 log_total_pred_CUE: natural log of total predator catch per unit effort
 #### File: bsm_analysis_meandatJuly2025.csv **Description:** mean trophic
 position and littoral coupling data from stable isotopes, lake
 morphometric data and competition variables used for the main analysis. 
 ##### Variables * Lake_Name: lake name * mean_LC_pred: mean lake trout
 littoral coupling * mean_TP_pred: mean lake trout trophic position *
 sampling_year: the year the lake was sampled * Area_ha: lake area in
 hectares * Secchi_depth: secchi depth in metres * summer_air_temp: mean
 summer air temperature in degrees Celsius  * LaTro_CUE: lake trout catch
 per unit effort * NoPik_CUE: northern pike catch per unit effort *
 Burbo_CUE: burbot catch per unit effort * Walle_CUE: walleye catch per
 unit effort * LmBas_CUE: largemouth bass catch per unit effort *
 Muske_CUE: muskellunge catch per unit effort * total_pred_CUE: total
 predator catch per unit effort * log_area_ha: natural log of lake area (in
 metres) * log_temp: natural log of mean summer air temperature (degrees
 celsius) * sqrt_temp: square root of mean summer air temperature (degrees
 celsius) * log_mean_TP_pred: natural log of mean lake trout trophic
 position * log_mean_LC_pred: natural log of mean lake trout littoral
 coupling * log_LaTro_CUE: natural log of lake trout catch per unit effort
 * log_total_pred_CUE: natural log of total predator catch per unit effort
 #### File: main_analysis_july20.R **Description:** Code for Main analysis:
 GAMM models and figures. #### File: full_lakes_july2025.csv
 **Description:** Data used for the supplementary analysis including the
 full lake set (52 lakes). ##### Variables * Lake_Name: lake name * SEAc:
 standard ellipse area (small sample size corrected) * dY_range: trophic
 position range * dX_range: range in proportion of nearshore carbon * TA:
 total area (isotopic niche area) * CD: centroid distance (isotopic) *
 NND: nearest neighbour distance (isotopic) * SDNND: standard deviation of
 nearest neighbour distance (isotopic) * sampling_year: year the lake was
 sampled * Area_ha: lake surface area (in hectares) * Secchi_depth: secchi
 depth (in metres) * summer_air_temp: mean summer air temperature in
 degrees celsius  * log_area_ha: natural log of lake area (in hectares) *
 log_dY_range: natural log of trophic position range *
 log_dX_range: natural log of proportion of nearshore carbon range *
 log_SEAc: natural log of standard ellipse area (small sample size
 corrected) * log_SDNND: natural log of standard deviation of nearest
 neighbour distance  #### File: supp_analysis_july20.R
 **Description:** Code for supplementary analysis. #### File:
 supp_dat_july2025.csv **Description:** Data for supplementary analysis on
 additional lake morphometrics ##### Variables * Lake_Name: lake name  *
 log_secchi: natural log of secchi depth (in metres) *
 log_dY_range: natural log of trophic position range *
 log_dX_range: natural log of proportion of nearshore carbon range *
 log_SEAc: natural log of standard ellipse area (small sample size
 corrected) * log_SDNND: natural log of standard deviation of nearest
 neighbour distance  * log_mean_LC_pred: natural log of lake trout mean
 littoral coupling * log_mean_TP_pred: natural log of lake trout mean
 trophic position * TP_ugL: Total phosphorus in micrograms per litre *
 Dev_Index: shoreline development index * pLittoral: proportion of littoral
 area * log_TP_ugL: natural log of total phosphorus (micrograms per litre)
 * log_Dev_Index: natural log of shoreline development index #### File:
 supp_dat_mean_july2025.csv **Description:** Data for supplementary
 analysis of full lake set.  ##### Variables * Lake_Name: lake name  *
 mean_LC_pred: mean lake trout littoral coupling * mean_TP_pred: mean lake
 trout trophic position * sampling_year: year the lake was sampled *
 Area_ha: lake area in hectares * Secchi_depth: secchi depth in metres *
 summer_air_temp: mean summer air temperature in degrees celsius  *
 log_area_ha: natural log of lake area (hectares) * log_temp: natural log
 of mean summer air temperature (degrees celsius) * sqrt_temp: square root
 of mean summer air temperature (degrees celsius) * log_mean_TP_pred:
 natural log of mean lake trout trophic position *
 log_mean_LC_pred: natural log of mean lake trout littoral coupling *
 logit_lc_pred: logit of mean lake trout littoral coupling ## Code/software
 R and R Studio can be used to view data and code. R can be used to run
 code to generate figures and analysis.