DOI: 10.5061/dryad.1jwstqk2m
title: Genetic variation in parasite avoidance, yet no evidence for constitutive fitness costs

description: Behavioral avoidance of parasites is a widespread strategy among animal
 hosts and in human public health. Avoidance has repercussions for both
 individual and population-level infection risk. Although most cases of
 parasite avoidance are viewed as adaptive, there is little evidence that
 the basic assumptions of evolution by natural selection are met. This
 study addresses this gap by testing whether there is a heritable variation
 in parasite avoidance behavior. We quantified behavioral avoidance of the
 bacterial parasite Serratia marcescens for 12 strains of the
 nematode host Caenorhabditis elegans. We found that these strains varied
 in their magnitude of avoidance, and we estimated the broad-sense
 heritability of this behavior to be in the range of 11-26%. We then asked
 whether avoidance carries a constitutive fitness cost. We did not find
 evidence of one. Rather, strains with higher avoidance had higher fitness,
 measured by population growth rate. Together, these results direct future
 theoretical and empirical work to identify the forces maintaining genetic
 variation in parasite avoidance.
description: # Genetic variation in parasite avoidance, yet no evidence for
 constitutive fitness costs
 [https://doi.org/10.5061/dryad.1jwstqk2m](https://doi.org/10.5061/dryad.1jwstqk2m) ## Description of the data and file structure The datasets and code in this repository accompany "Genetic variation in avoidance, yet no evidence for constitutive costs," by Caroline R. Amoroso, Leila L. Shepard, and Amanda K. Gibson. In the Data folder are two files: **1. "Lawn-leaving assay.csv":** the original data collected for this project on the parasite avoidance behavior of *C. elegans* strains. Explanations of column headers: Block: experimental block, 1 through 6 Plate_number: replicate plate Bacterial_strain: OP50 (*E. coli* control) or Db10 (*S. marcescens* parasite) C.elegans_strain: Code corresponding to one of 12 of the *C. elegans* strains from the CaeNDR "divergent set"" (see [https://caendr.org/request-strains/](https://caendr.org/request-strains/)) Date_time_picked: Date and time that *C. elegans* hosts were added to the experimental plate Date_time_counted: Date and time that *C. elegans* hosts were scored as on or off the bacterial lawn Worms_ON: count of hosts on the lawn Worms_OFF: count of hosts off the lawn N_dead_worms: Number of dead worms (these were always on the lawn) N_burrowed: Number of worms burrowed into agar (these were always under the lawn of OP50) Excl_from_sub20: Sum of dead or male worms by subtracting "avoided" from 20 (analysis with a liberal interpretation of avoidance) **2. "Population growth assay.csv":** Original data collected for this project on the fitness of 12 strains of *C. elegans*. Explanations of column headers: Block: experimental block, 1 through 5 Strain: C. elegans strain code, same as above Plate: replicate plate number Drop: Which of 4 to 6 20 ul drops was counted for the number of *C. elegans* individuals, reflecting the population size after a fixed period of population growth Count_20ul: Mean of 3 separate counts of each 20ul drop Burrowing_exclude: removed two replicates because *C. elegans* individuals had burrowed into agar, interfering with our ability to wash them from plates and count them. **We do not provide a file that we used in the analysis due to copyright restrictions.** In our code this file is referred to as "Zhang et al 2021 fecundity data.csv". These data are previously published, independent measures of fitness from another lab for 7 of the 12 strains in the present study. Downloaded from [https://github.com/AndersenLab/swept_broods/blob/main/processed_data/FileS3_lifetimeFecundity.csv](https://github.com/AndersenLab/swept_broods/blob/main/processed_data/FileS3_lifetimeFecundity.csv); from Zhang et al. 2021 Natural variation in fecundity is correlated with species-wide levels of divergence in *Caenorhabditis elegans*. G3. [https://doi.org/10.1093/g3journal/jkab168](https://doi.org/10.1093/g3journal/jkab168). The paper is available at [https://academic.oup.com/g3journal/article/11/8/jkab168/6275220](https://academic.oup.com/g3journal/article/11/8/jkab168/6275220) Links to other publicly accessible locations of the data: [https://github.com/carolineramoroso/C.elegans_Genetic_variation_in_avoidance](https://github.com/carolineramoroso/C.elegans_Genetic_variation_in_avoidance) ## Code/Software Analysis can be found in "Genetic variation in parasite avoidance_analysis.R" and relies on the above described data files.