DOI: 10.5061/dryad.vhhmgqp2t
title: Resistance and tolerance to imperfectly specialized parasites: Milkweed butterflies and their protozoan parasites

description: Understanding host specificity and cross-species transmission of parasites
 is crucial for predicting the risk and consequences of parasite spillover.
 We experimentally examined these dynamics in two closely related,
 sympatric, milkweed butterfly hosts: monarchs (Danaus plexippus) and
 queens (D. gilippus). The debilitating protozoan Ophryocystis
 elektroscirrha (OE) infects wild monarchs throughout their range, and
 similar neogregarine parasites have been reported from queens. We compared
 host resistance and tolerance to infection between hosts exposed to
 parasites of conspecific and heterospecific origin and examined whether
 differences in immune investment reflected variation in infection
 outcomes. Results showed that monarchs were highly susceptible to both
 conspecific and heterospecific parasites. In contrast, queens were
 susceptible almost exclusively to conspecific parasites. Queens showed
 greater tolerance to infection and greater immune defense in the form of
 melanization activity and concentrations of encapsulating hemocytes.
 Additionally, monarch parasites caused higher pre-adult mortality and more
 wing deformities than queen parasites. Given that OE can reduce monarch
 abundance and migratory performance, and that monarchs overlap with
 butterflies that host similar parasites, quantifying cross-infection
 outcomes is important for conservation management of these two butterfly
 species. The greater susceptibility and costs of infection in monarchs
 suggest potential fitness trade-offs against resistance and tolerance to
 infection in migratory hosts and underscores the need to identify factors
 that limit hosts’ adaptation to parasites.
description: We performed controlled cross-infection experiments on monarch
 and queen butterflies using conspecific and heterospecific parasite
 strains. Caterpillars were assigned to receive either no parasites,
 parasites from queens, or parasites from monarchs. Within each
 host-parasite source combination, caterpillars were fed either swamp or
 tropical milkweed from the day of inoculation until pupation. This design
 resulted in 12 treatment combinations of butterfly species x parasite
 source x plant diet combinations. A subset of caterpillars was bled at the
 5tth instar to estimate hemocyte concentration, hemocyte differentials,
 and the activity of the enzyme phenoloxidase as metrics of immune defense.
 We quantified measures indicative of host fitness and to inform analyses
 of host resistance and tolerance to infection.
description: # Resistance and tolerance to imperfectly specialized parasites: Milkweed
 butterflies and their protozoan parasites
 [https://doi.org/10.5061/dryad.vhhmgqp2t](https://doi.org/10.5061/dryad.vhhmgqp2t) ## Description of the data and file structure Code and data files to perform the analysis of milkweed butterfly resistance and tolerance to OE and OE-like parasites. R scripts were created sequentially (1-6), and would need to be run sequentially to recreate the analysis. However, RDATA files are provided and saving commands have been commented out so that each file can be run independently and files are not overwritten. R scripts can be run using the provided raw data files (CSV and described below). In all data files NA = not available/not applicable ### Main data files #### Clean compiled final dataset data_mwv_resist_tol.csv #### Data dictionary to accompany "data\_mwv\_resist\_tol.csv" data_dictionary_mwv_resist_tol.csv ### Raw data files ##### Sex, weight, eclosion data, and pupal infection scores per individual adult_scores.csv ##### Experimental results, pre-cleanup cross-inf-exp.csv ##### Hemocyte counts and differencials mq-hemocyte_counts.csv ##### Absorbance reads per time from phenoloxidase assays po-reads.csv ##### Oocyst counts per individual spore_loads.csv ##### Average pixel density of all black portions of the wing wing_color_black.csv ##### Forewing characteristics by individual wing_features.csv ## Code/Software ### R code scripts provided. Scripts were created in R version 4.0.4 #### Data cleanup from cross-infection experiment 1_data.cleanup.R #### Compile, summarize, and analyze data from phenoloxidase (PO) assays 2a_imm_PO.R #### Analyze data from PO assays (statistical models) 2b_imm_PO_models.R #### Visualize PO curves 2c_PO_curves.R #### Compile, summarize, and analyze data from immune cells density and differentials 3_imm_cellular.R #### Compile, summarize, and analyze butterfly fitness outcomes 4_fitness.R #### Compile, summarize, and analyze infection outcomes; butterfly resistance, and tolerance 5_outcome.R #### Format and compile the main figures 6_compile_figure.R