Data from: Host plants and experimental warming impact fitness and infection outcomes in a migratory butterfly
Data files
Aug 21, 2025 version files 801.59 KB
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AverageAmbient_RelHum.csv
140.42 KB
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AverageAmbient_TEMP2.csv
231.59 KB
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AverageElevated_RelHum.csv
143.85 KB
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AverageElevated_TEMP.csv
236.26 KB
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MWwarming_comp_May16.csv
34.71 KB
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per_ibutton_avgtemps_full.csv
1.91 KB
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README.md
10.58 KB
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UGA_Cardenolide_Analysis_March2023_tropical.csv
2.26 KB
Abstract
Climate warming can impact host and parasite traits directly, but higher temperatures also affect parasitism indirectly through species interactions like herbivory. Given that temperature can influence plant quality, which in turn shapes nutrition and immune defense of insect herbivores, understanding plant-mediated effects of warming on insect-parasite interactions could inform insect conservation and pest management. We examined how warming and host plant species influenced parasitism of monarch butterfly (Danaus plexippus) larvae by the protozoan parasite Ophryocystis elektroscirrha (OE) in a field cage experiment. Cardenolides, defensive chemicals produced by milkweed host plants (Asclepias spp.), increase monarch tolerance and resistance to OE. We reared parasite-exposed and uninfected control monarch larvae on tropical (high-cardenolide) or swamp (low-cardenolide) milkweed in either ambient or elevated temperatures, measuring monarch development, survival, and size, and OE infection success and intensity. To assess whether temperature effects on infection or monarch traits are influenced by altered milkweed nutrition or toxicity, we measured foliar carbon, nitrogen, and cardenolides. We found that host plant species was an important predictor of monarch development and survival, and that elevated temperatures reduced monarch tolerance to infection even when reared on high-cardenolide tropical milkweed. We also found that milkweed leaves had more nitrogen relative to carbon in temperature-elevated plots, indicating that despite improved host plant nutrition, monarchs experienced lower fitness and higher costs of infection. These findings will help predict consequences of warming for monarch health across the insect’s range, especially for southerly latitudes where tropical milkweed supports monarch residency and high OE infection risk.
https://doi.org/10.5061/dryad.prr4xgxx7
Description of the data and file structure
Contained here are datasets describing monarch performance, parasite infection outcomes, and plant traits from a field experiment manipulating milkweed host plant species and temperature. The code used to perform statistical analysis and visualize results is also included.
Files and variables
File: UGA_Cardenolide_Analysis_March2023_tropical.csv
Description: This file contains the cardenolide toxin measures for the subset of tropical milkweeds sampled from the field
Variables
- Plant_ID: unique identification number for each plant
- total card conc: total cardenolide concentration (mg/g dry mass)
- sum of polarity: overall polarity of a plant's cardenolides; a metric that represents the toxicity of the plant's cardenolide compounds; "NA" if "total card conc" = 0
- plot num: number representing physical location in the field plot
- Temp: ambient or elevated temperature
- OE_treat: infected or uninfected control
- Milkweed_sp: tropical or ambient
- Lineage: monarch genetic lineage (A, B, C, or E)
- Strain: parasite genetic strain (WV1 or E6) or C for control
- ibutton_num: name of temperature/humidity data logger in plot ("na" if not available)
File: AverageAmbient_TEMP2.csv
Description: Temperature (°C) reading for each of the ibuttons in ambient plots in all timesteps across the experiment. Calculated the mean and standard deviation of temperature for each timestep. (Date/Time is the exact value from ibutton H1; other ibuttons recorded temperature within 10 minutes of H1)
Variables
- Timestep: 1 to 1600, ibuttons recorded temperature every 20 minutes throughout the experiment
- Date/Time: (pulled from ibutton H1)
- Unit: all temperatures recorded in Celsius (°C)
- H# or T#: unique names for each ibutton; columns contain that ibutton's recorded temperatures for each timestep ("NA" = not applicable if ibutton did not record during a timestep)
- AverageTemp: arithmetic mean of temperatures within a timestep, averaging across all ibuttons with values recorded
- Stdev: standard deviation of temperatures within a timestep
File: AverageAmbient_RelHum.csv
Description: Relative Humidity (%) reading for each of the ibuttons in ambient plots in all timesteps across the experiment. Calculated mean and standard deviation of RH for each timestep. (Date/Time is the exact value from ibutton H1)
Variables
- Timestep: 1 to 1600, ibuttons recorded every 20 minutes throughout the experiment
- Date/Time: (pulled from ibutton H1)
- Unit: all hygrometer ibuttons recorded percent relative humidity (%RH)
- H#: unique names for each ibutton; columns contain that ibutton's recorded %RH for each timestep ("NA" = not applicable if ibutton did not record during a timestep)
- Average_RH: arithmetic mean of %RH within a timestep, averaging across all ibuttons with values recorded
- Stdev: standard deviation of %RH within a timestep
File: AverageElevated_RelHum.csv
Description: Relative Humidity (%) reading for each of the ibuttons in elevated temperature plots in all timesteps across the experiment. Calculated mean and standard deviation of RH for each timestep. (Date/Time is the exact value from ibutton H2)
Variables
- Timestep: 1 to 1600, ibuttons recorded every 20 minutes throughout the experiment
- Date/Time: (pulled from ibutton H2)
- Unit: all hygrometer ibuttons recorded percent relative humidity (%RH)
- H#: unique names for each ibutton; columns contain that ibutton's recorded %RH for each timestep ("NA" = not applicable if ibutton did not record during a timestep)
- Average_RH: arithmetic mean of %RH within a timestep, averaging across all ibuttons with values recorded
- Stdev: standard deviation of %RH within a timestep
File: AverageElevated_TEMP.csv
Description: Temperature (°C) reading for each of the ibuttons in elevated temperature plots in all timesteps across the experiment. Calculated the mean and standard deviation of temperature for each timestep. (Date/Time is the exact value from ibutton H2; , other ibuttons recorded within 10 minutes of H2)
Variables
- Timestep: 1 to 1600, ibuttons recorded temperature every 20 minutes throughout the experiment
- Date/Time: (pulled from ibutton H2)
- Unit: all temperatures recorded in Celsius (°C)
- H# or T#: unique names for each ibutton; columns contain that ibutton's recorded temperatures for each timestep ("NA" = not applicable if ibutton did not record during a timestep)
- AverageTemp: arithmetic mean of temperatures within a timestep, averaging across all ibuttons with values recorded
- Stdev: standard deviation of temperatures within a timestep
File: per_ibutton_avgtemps_full.csv
Description: Mean, standard deviation, and standard error of recorded temperatures for each ibutton
Variables
- Temp_treatment: ambient or elevated
- ibutton_ID: unique identification of temperature/humidity data logger in plot
- lag: (time offset relative to reference ibutton)
- relative: (whether the ibutton was several minutes ahead or behind)
- variable: Temp = temperature (not relative humidity)
- n: number of recorded temperatures
- mean: arithmetic mean of all temperatures recorded per ibutton across entire experiment
- sd: standard deviation of all temperatures recorded per ibutton across entire experiment
- se: standard error of all temperatures recorded per ibutton across entire experiment
- PlotNum: number representing physical location in the field plot
File: MWwarming_comp_May16.csv
Description: Comprehensive data table with monarch performance and infection metrics in addition to plant measures for the subset of milkweed plants sampled
Variables
- ID: unique identification number for each monarch
- Plant_ID: unique identification number for each host plant
- Temp: ambient or elevated
- OE_treatment: infected or uninfected control
- Milkweed: tropical or swamp
- Lineage: monarch genetic lineage (A, B, C, or E)
- Strain: parasite genetic strain (WV1 or E6) or C for control
- PlotNum: number representing physical location in the field plot
- ibutton: unique name of the ibutton data logger
- Surv_pupa: survival to pupation (1/0) 1=yes, 0=no
- Surv_adult: survival to adult (1/0) 1=yes, 0=no
- PupalMass: mass of pupa (g); "NA" if monarch died prior to pupal stage
- Date_inoculated: date larva fed inoculum or sham
- Date_into_pint: date pupa removed from field and placed in individual pint container
- PupalScore: For all inoculated monarchs, pupae were scored on a 0-5 scale for signs of OE infection (level of black spotting); "NA" = not applicable (monarch was dead or in the control group, and therefore not assessed); "missed" = monarch eclosed before scoring
- Date_PupScore: date pupa was scored for OE; "NA" if monarch died prior
- Eclosion_Date: date adult monarch emerged; "NA" if monarch died prior
- Sex: M or F (determined at adult stage); "NA" if monarch died prior
- OE_tape_score: for uninoculated control monarchs, we checked for OE contamination by pressing clear plastic tape to adult abdomens and checking for OE under the microscope. We also checked inoculated monarchs with low pupal scores, scoring them on a scale from 0-5. "NA" if not sampled.
- InfectionStatus: binary presence/absence of OE (1/0); 1=yes, 0=no
- Death_date: date adult monarch died; "NA" if monarch died prior to adult stage
- Notes: including observations on stage/cause of death, empty cell if nothing was noted
- Inoc_to_pupa: time in days from inoculation to pupa (averaged for the two caterpillars on each plant if they pupated on different days); "NA" if monarch died prior to pupation
- AdultLongevity: days monarchs survived in the adult stage at 12C; "NA" if monarch died prior to adult stage
- AvgOE_corner: average number of OE spores in one grid square of hemocytometer (used in infection intensity calculation), not applicable ("NA") for control monarchs or those that died prior to the adult stage
- OE_5ml: Spore load (calculated number of spores per monarch based on "AvgOE_corner")
- LogOE: Log10 transformation~ ~of "OE_5ml"
- ForewingLength.mm.: length of forewing measured with calipers (mm); "NA" if monarch died prior to adult stage
- CtoN: Carbon to Nitrogen ratio of the host plant (only for the subset of sampled plants; "NA" if not)
- CtoN_Jul: Carbon to Nitrogen ratio of plants (only if resampled at end of experiment; "NA" if not)
Code/software
Statistical analyses were completed in R (version 4.4.1). Code was implemented using loaded packages: tidyverse, dplyr, ggplot2, lme4, lubridate, stats, MuMIn, rstatix, MASS, Hmisc, ggpubr, car, DescTools, sjplot, and emmeans
Files:
"MWwarming_2021.Rproj": R project that bundles the relevant scripts and data files used for the analysis. Save project file in the same folder as the above data (.csv) files and the markdown (.rmd) files below. Open the project in R Studio and then access the markdown files within the project.
("MW_warming_Nov_2024.rmd": Data analysis and visualization for a 2021 field experiment exploring the effects of elevated temperature, milkweed host plant species, and the interaction between milkweed and temperature on monarch traits and infection.)
"MW_warming_Jul_2025.rmd": *Revised Nov 2024 rmd file; Most up-to-date version of visualizations from manuscript revision. Data analysis and visualization for a 2021 field experiment exploring the effects of elevated temperature, milkweed host plant species, and the interaction between milkweed and temperature on monarch traits and infection.
- temperature data: "per_ibutton_avgtemps_full.csv" ;
- monarch data: "MWwarming_comp_May16.csv"
- plant data: "UGA_Cardenolide_Analysis_March2023_tropical.csv"
"ibutton_temp.rmd": Mean daily temperature (°C) comparison and repeated ANOVAs for ambient vs. temperature-elevated plots
"ibutton_humidity.rmd" : Mean daily relative humidity (%) comparison and repeated ANOVAs for ambient vs. temperature-elevated plots
Access information
Other publicly accessible locations of the data:
We reared parasite-exposed and uninfected control monarch larvae on tropical (high-cardenolide) or swamp (low-cardenolide) milkweed in either ambient or elevated temperatures in field plots. We measured monarch development, survival, and size, and OE infection success and intensity. To assess whether temperature effects on infection or monarch traits are influenced by altered milkweed nutrition or toxicity, we measured foliar carbon, nitrogen, and cardenolides.
We tested for the effects of plot temperature (ambient/elevated), milkweed species (swamp/tropical), and infection (inoculated/uninoculated) treatments on monarch fitness and parasite infection outcomes using linear and generalized linear models (GLMs). For each response variable, we assessed a small set of candidate models: an uninformative null, a model containing main effects, and models containing interaction terms of interest.