Quantitative support for the metabolic load hypothesis: Metabolic rate measures reveal host-dependent growth costs in a polyphagous herbivore

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. T..., , # Data from: Quantitative support for the metabolic load hypothesis: Metabolic rate measures reveal host-dependent growth costs in a polyphagous herbivore

Dataset DOI: [10.5061/dryad.gb5mkkx42](https://doi.org/10.5061/dryad.gb5mkkx42)

## Description of the data and file structure

We collected data on growth rate and metabolic rate from three developmental stages (3^rd^ larval instar, 4^th^ 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

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