Butterfly host plant use driven by microclimate not nutritional quality
Data files
Feb 11, 2026 version files 104.41 KB
-
egg_laying_data.csv
85.48 KB
-
plant_chemistry_data.csv
11.76 KB
-
README.md
7.17 KB
Abstract
The abundance of insect herbivores often depends on host plant suitability for their specialised immature stages. Suitability can be strongly influenced by both microclimate and the nutritional quality of the plants themselves. Where soil nitrogen is high, host plants tend to have high nutritional quality, but vigorous growth of surrounding vegetation reduces microclimatic temperatures. Thus, thermophilous insects may face a choice between host plants with optimal microclimates and those with optimal nutritional quality. We investigated how microclimate and nitrogen content influence oviposition choices by the declining Small Copper butterfly, Lycaena phlaeas, on its host plant, Rumex acetosa. We predicted that warmer plants would have lower nitrogen content, and that butterflies would choose cooler, high-nitrogen plants during warmer ambient conditions. Although warmer R. acetosa plants had lower nitrogen content, L. phlaeas consistently chose to lay eggs on plants in warm microclimates, implying a trade-off between temperature and the nutritional quality of host plants. Patches of bare ground created by European Moles (Talpa europaea) near R. acetosa plants increased microclimatic temperatures and decoupled the negative correlation between nutritional quality and thermal suitability. Our results have implications for the conservation of thermophilous insect herbivores, especially close to their range margins and in the context of climate change. Rather than maximising host plant abundance or nutritional quality, management that creates suitable microclimatic conditions is likely to be critical. Our findings also suggest that, while nitrogen pollution may increase host plant nutritional quality, its negative impacts on microclimate will likely further reduce breeding habitat for L. phlaeas and other insects in grassland habitats.
Dataset DOI: 10.5061/dryad.hqbzkh1wk
Description of the data and file structure
Data collected to support investigations into the role of microclimate around host plants and nutritional quality of host plants in shaping oviposition by a specialist herbivorous butterfly. Each row in the dataset is a host plant, either a plant with one or more eggs or larvae (plant_id contains 'e') or a control plant next to an occupied plant (in a randomly selected direction) (plant_id contains 'c').
There are two datasets, one smaller dataset (plant chemistry data) which contains chemical data for a sample of host plants along with data on possible proxies for this chemical data. This data was used to identify the best proxies for host nutritional quality (nitrogen content).
The second larger dataset was then used for all further analyses. It contains data about host plant chemistry proxies, predicted host plant chemistry, the environment around them, the presence of butterfly eggs and larvae.
The plants in the first dataset are largely a subset of those represented in the second, but several plants in the smaller dataset were later removed from the main analysis, and retained for the proxy analysis, hence the separate datasets.
Files and variables
File: egg_laying_data.csv
Description:
Variables
- predicted_n: Predicted nitrogen content of host plant, micromoles per g.
- n_se: standard error around predicted nitrogen content of host plant.
- n_weights: inverse of standard error around predicted nitrogen content of host plant.
- plant_id: unique identifier for host plant, a 'c' denotes a control plant, and 'e' a plant with butterfly eggs or larvae.
- id_number: numeric component of plant_id
- species: host plant species, all ra as all host plants were Rumex acetosa.
- season: season in which host plant was sampled, either autumn or spring (referred to as early summer in manuscript).
- n_eggs: number of eggs on plant
- larvae: number of larvae on plant
- occupied: whether the plant was occupied with butterfly eggs or larvae (based on preceding two columns).
- gps: British national grid reference of host plant
- bare_ground: %cover of bare ground around host plant, in 50cm grid with host plant at centre.
- veg: %cover of vegetation around host plant, in 50cm grid with host plant at centre.
- litter: %cover of litter around host plant, in 50cm grid with host plant at centre.
- sward_height: sward height (cm) around host plant, measured using direct method (see manuscript).
- plant_area: estimated area of host plant (in cm2, based on perpendicular dimensions of tightest fitting square - plant_size_1 multiplied by plant_size_2)
- bare: whether or not bare ground was present in the 50cm grid around the host plant.
- plant_size_1: One dimension of plant used to calculate plant area (cm).
- plant_size_2: One dimension of plant used to calculate plant area (cm).
- leaf1_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf2_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf3_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf1_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf2_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf3_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf1_area: Area of a sampled leaf (mm2).
- leaf2_area: Area of a sampled leaf (mm2).
- leaf3_area: Area of a sampled leaf (mm2).
- total_leaf_area: Sum of areas of sampled leaves (mm2).
- leaves_sampled: Number of leaves from host plant sampled
- average_leaf_size: Average area of sampled host plant leaves (mm2)
- temperature_soil: Temperature measured at soil surface under host plant (degrees Celsius).
- temperature_ambient: Ambient temperature measured while measuring soil surface temperature under host plant (degrees Celsius).
- environment_date: Date on which environmental measurements for host plant were taken.
- temperature_date: Date on which temperature measurements for host plant were taken.
- date_mean_soil: Mean soil surface temperature of host plants measured on the same date as plant in that row.
- date_sd_soil: Standard deviation of soil surface temperatures of host plants measured on the same date as plant in that row.
- temperature_soil_scaled: Soil surface temperature under host plant, scaled and centred by sampling date to express whether a host plant was warmer or cooler than others measured on the same date.
- scaled_leaf_size: Centred and scaled average leaf area for host plant.
- scaled_n_content: Centred and scaled predicted nitrogen content for a host plant.
File: plant_chemistry_data.csv
Description:
Variables
- plant_id: Unique identifer of host plant.
- N: % nitrogen content of host plant by mass
- C: % carbon content of host plant by mass
- cn_percent: Carbon : Nitrogen ratio of host plant by mass
- n_molar: Molar nitrogen content of host plant (micromoles per g).
- c_molar: Molar carbon content of host plant (micromoles per g).
- cn_molar: Molar Carbon : Nitrogen ratio of host plant
- plant_size_1: One dimension of plant used to calculate plant area (cm).
- plant_size_2: One dimension of plant used to calculate plant area (cm).
- plant_area: Estimated area of host plant (in cm2, based on perpendicular dimensions of tightest fitting square - plant_size_1 multiplied by plant_size_2)
- leaf1_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf1_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf2_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf2_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf3_length: Length of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf3_width: Width of a sampled leaf used to calculate leaf area and average ultimately leaf size (mm).
- leaf1_area: Area of a sampled leaf (mm2).
- leaf2_area: Area of a sampled leaf (mm2).
- leaf3_area: Area of a sampled leaf (mm2).
- total_leaf_area: Sum of areas of sampled leaves (mm2).
- leaves_sampled: Number of leaves from host plant sampled
- average_leaf_size: Average area of sampled host plant leaves (mm2)
- season: Season in which host plant was sampled, autumn or spring (early summer in manuscript).
- quality_PC1: Value of first principal component of PCA of average leaf size and plant area for host plant.
- quality_PC2: Value of second principal component of PCA of average leaf size and plant area for host plant.
Code/software
Datasets viewed in Microsoft excel, and analysed using R and R studio.