DOI: 10.5061/dryad.8sf7m0czp
title: Data from: Crowding reduces per-capita parasite infection risk in a butterfly host

description: Crowding can result in greater disease transmission, yet crowded hosts may
 also remove infectious propagules from the environment, lowering the
 encounter rate and infectious dose of conspecifics. We combined
 experimental and modeling work to examine the impact of crowding of
 butterfly larvae on per-capita infection risk by a protozoan that is
 transmitted via the larval food plant, and the resulting infection load in
 adult butterflies. We reared larvae at different densities and mimicked
 low and high doses of parasites. We modified an existing model to include
 effects of conspecific density on food (and thus parasite) consumption
 rate and infected adult mortality rate. Experimental work indicated that
 infection rates on plants with ten caterpillars were reduced by at least
 50% compared to single caterpillars. High density reduced individual
 infection risk and parasite load and extended the lifespan of all hosts,
 as crowded hosts removed parasites from the environment. Modeling
 suggested that the lower consumption rate due to crowding can lower
 infection prevalence by as much as 20%; however, the total number of
 infected individuals increases. Our results highlight that the expected
 positive relationship between host density and infection prevalence breaks
 down when crowding removes infectious particles from the environment.
description: # Crowding reduces parasite infection risk and virulence in a butterfly
 host
 [https://doi.org/10.5061/dryad.8sf7m0czp](https://doi.org/10.5061/dryad.8sf7m0czp) ## Description of the data and file structure This dataset includes the necessary data and code to reproduce the analyses in the manuscript entitled "Crowding reduces parasite infection risk and virulence in a butterfly host". In this study, we combined experimental and modeling approaches to investigate how crowding of butterfly larvae affects their infection risk from a protozoan parasite transmitted through the larval food plant, as well as the resulting infection load in adult butterflies. We reared larvae at varying densities and simulated different transmission rates by exposing them to low and high doses of parasites. An existing model was modified to account for the effects of conspecific density on food and parasite consumption rates, as well as infected adult mortality. All missing data are represented as NA. ### Files and variables #### Data File: Experiment1.csv **Description:** Data in tidy format from experiment 1 of the study. Contains the variables used for the analysis. "NA" indicates no data in a given cell. * **MonarchID**: Unique identifier using a combination of letters and numbers for individual monarchs in the study. * **TubeID**: Unique identifier using a combination of letters and numbers for tubes in which monarch caterpillars were held. * **Treatment**: Categorical variable indicating treatment: uninfected or infected. * **Density**: Categorical variable indicating the density at which monarch caterpillars were held in the tube: single or ten * **Dose**: Number of spores deposited on the milkweed plant: 0, 10, or 100 * **Replicate**: Numerical variable indicating replicate number for the treatment dose combination. * **Hatch_date**: The date of egg hatching in the format month/day/year. * **Inoc_date**: The date when a plant was inoculated with parasite spores in the format month/day/year. * **Pupation_date**: The date of the caterpillar pupating in the format month/day/year. * **Eclosion_date**: The date of pupa eclosing in the format month/day/year. * **Adult_death_date**: The date of adult death in the format month/day/year. * **lSL5**: Log of the spore load on the monarch. * **InfectedLS**: Binary variable indicating whether the monarch was infected (indicated as 1) or not infected (indicated as 0) based on the log spore load. * **Adult Longevity**: The number of days an adult monarch lived. #### Data File: Experiment2.csv **Description:** Data in tidy format from experiment 2 of the study. Contains the variables used for the analysis. "NA" indicates no data in a given cell. * **MonarchID**: Unique identifier using a combination of letters and numbers for individual monarchs in the study. * **TubeID**: Unique identifier using a combination of letters and numbers for tubes in which monarch caterpillars were held. * **Treatment**: Categorical variable indicating treatment: uninfected or infected. * **Density**: Categorical variable indicating the density at which monarch caterpillars were held in the tube: single, double, ten * **Dose**: Number of spores deposited on the milkweed plant: control, low, high * **Replicate**: Numerical variable indicating replicate number for the treatment dose combination. * **Hatch_date**: The date of egg hatching in the format month/day/year. * **Inoc_date**: The date when a plant was inoculated with parasite spores in the format month/day/year. * **Pupation_date**: The date of the caterpillar's pupating in the format month/day/year. * **Eclosion_date**: The date of pupa eclosing in the format month/day/year. * **Adult_death_date**: The date of adult death in the format month/day/year. * **lSL5**: Log of the spore load on the monarch. * **InfectedLS**: Binary variable indicating whether the monarch was infected (indicated as 1) or not infected (indicated as 0) based on the log spore load. * **Adult Longevity**: The number of days an adult monarch lived. ### Software files #### File: ExperimentalDataScript.R **Description:** This R script allows for the reproduction of the experimental portion of the study. The script imports experimental data (Experiment1.csv and Experiment2.csv) and runs code for statistical analyses. The code produces figures and tables for each experiment. Tables are saved as Word documents. #### File: MonarchOEmodelForagingDilution.R **Description:** This R script includes the stage-structured mechanistic mathematical model of the monarch-OE system. #### File: ForageDilutionRProject.zip **Description:** This zipped folder contains all the standalone data and R script files above (Experiment1.csv, Experiment2.csv, ExperimentalDataScript.R, MonarchOEmodelForagingDilution.R) and an R project to reproduce the analyses. * **Forage Dilution.Rproj**: R project file that, when opened first, ensures correct dependency paths for the R scripts. ## Code/software All analyses and simulations were performed in R (R version 4.4.1).