Resistance and tolerance to imperfectly specialized parasites: Milkweed butterflies and their protozoan parasites

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..., 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., , # 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, a...,