Data from: Quantitative support for the metabolic load hypothesis: Metabolic rate measures reveal host-dependent growth costs in a polyphagous herbivore
Data files
Feb 02, 2026 version files 93.53 KB
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Growth_rate.csv
41.85 KB
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Metabolic_cost_analysis.R
17.37 KB
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Metabolic_rate.csv
30.13 KB
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README.md
4.18 KB
Abstract
The interactions between phytophagous insects and their host plants show a strong trend towards specialization. However, the reasons behind this trend remain largely unclear, at both the evolutionary and mechanistic levels. One possible explanation is an increased energy expenditure for digesting and metabolizing more challenging hosts included in a broader host repertoire, which may reduce the energy available for other processes such as growth and development (“metabolic load hypothesis”). Differences in the performance across various hosts could reflect such costs. Using the polyphagous Polygonia c-album (comma butterfly), we tested whether observed performance differences can be linked to variation in the energetic requirements. For this, we measured the metabolic rate of larvae feeding on three different host plants and converted it into the amount of CO2 produced per gram of mass gain (“growth cost”) to assess how much energy is allocated to growth vs digestion and assimilation. The metabolic rate of larvae feeding on a chemically more challenging plant (Ribes uva-crispa) was similar to that of individuals on the host supporting the highest growth rate (Urtica dioica). However, larvae on Ribes uva-crispa exhibited a higher energy demand per unit of growth and a lower growth rate, indicating a different energy allocation in growing larvae than when they were reared on a chemically less challenging plant. Our findings suggest that energy expenditure for digesting different hosts varies and can have direct consequences for larval performance. This indicates that the trend towards ecological specialization may, at least partly, be driven by selection to reduce the energetic costs for detoxification and digestion, in support of the metabolic load hypothesis.
Dataset DOI: 10.5061/dryad.gb5mkkx42
Description of the data and file structure
We collected data on growth rate and metabolic rate from three developmental stages (3rd larval instar, 4th larval instar, pupa) of the polyphagous comma butterfly, Polygonia c-album, reared on one of three host plants: Urtica dioica, Salix caprea, or Ribes uva-crispa. Data for the performance measurements (i.e., growth rate) are provided in "Growth_rate.csv", and data including the metabolic rate measurements are available in "Metabolic_rate.csv". To quantify the costs of feeding on each host plant, we calculated the growth costs as the energy required for 1g of mass increase. The R script used for the analysis is provided in "Metabolic_cost_analysis.R".
Files and variables
File: Metabolic_rate.csv
Description: The metabolic rate was measured as the amount of CO2 produced within one hour
Variables
- sample: ID to identify the individual and the developmental stage at which the metabolic rate was measured
- plant: Host plant on which the measured individual was reared
- life.stage: developmental stage at which the metabolic rate was measured
- id2: ID to identify an individual without information on the developmental stage
- mass in g: larval or pupal weight measured before the metabolic rate assessment in grams (NA = not available)
- vco2(ml/min): Volume of produced CO2 in milliliter per minute
- vco2(ml/hr): Volume of produced CO2 in milliliter per hour
File: Growth_rate.csv
Description: Growth rate was calculated as the logged larval mass divided by the developmental time (in days) until the measurement
Variables
- Individual: ID to identify the individual
- Host: Host plant on which the individual was reared
- Mother: ID of mother individual
- Father: ID of father individual (NA = not available)
- Coll. date: date on which eggs were collected from host plant (24-hour windows of oviposition)
- hatching_date: date on which a larva hatched and was moved to one of the three host plants
- date_i3: date on which a larva reached the 3rd larval instar (NA = not available)
- weight_i3: weight of a larva after reaching the 3rd larval instar (NA = not available)
- date_i4_d1: date on which a larva reached the 4th larval instar (NA = not available)
- weight_i4_d1: weight of a larva after reaching the 4th larval instar (NA = not available)
- date_pupa_MR: date on which individual reached pupal stage (NA = not available)
- days_till_pupa: days from hatching to pupation (NA = not available)
- pupal_weight: weight of pupa (weighed 1 day after pupation was completed; NA = not available)
- sex : sex of individual (F=female, M=male, NA=not available)
- Dev.t_i4_d1: Developmental time from hatching until a larva reached the 4th larval instar (in days; NA = not available)
- Growth_rate_i4d1: Growth rate calculated as the logged larval mass divided by the developmental time (in days) until reaching the 4th instar (NA = not available)
- Growth_rate_P: Growth rate calculated as the logged pupal mass divided by the developmental time (in days) until pupation (NA = not available)
- MR_i3: Summary if metabolic rate was measured in the 3rd larval stage (Y=yes, N=no)
- MR_i4: Summary if metabolic rate was measured in the 4th larval stage (Y=yes, N=no)
- MR_P: Summary of metabolic rate was measured at the pupal stage (Y=yes, N=no)
File: Metabolic_cost_analysis.R
Description: R script used for the analysis of the growth rate and metabolic rate data
Code/software
All data preparation, analysis, and visualization were performed in R (version 4.2.2). Information on all the used packages and versions is provided in Metabolic_cost_analysis.R under "packages".
Access information
Other publicly accessible locations of the data: