DOI: 10.5061/dryad.zw3r22869
title: An experimental test of parasite adaptation to common vs. rare host genotypes

description: A core hypothesis in coevolutionary theory proposes that parasites adapt
 to specifically infect common host genotypes.  Under this
 hypothesis, parasites function as agents of negative frequency-dependent
 selection, favoring rare host genotypes.  This parasite-mediated
 advantage of rarity is key to the idea that parasites maintain genetic
 variation and select for outcrossing in host populations.  Here,
 we report the results of an experimental test of parasite adaptation to
 common vs. rare host genotypes.  We selected the bacterial
 parasite Serratia marcescens to kill C. elegans hosts in uneven mixtures
 of host genotypes.  To examine the effect of commonness itself,
 independent of host identity, each of four host genotypes was represented
 as common or rare in experimental host mixtures.  After
 experimental selection, we evaluated a parasite line’s change in
 virulence, the selected fitness trait, on its rare and common host
 genotypes.  Our results were consistent with a slight advantage
 for rare host genotypes: on average, parasites lost virulence against rare
 genotypes but not against common genotypes.  The
 response varied substantially, however, with distinct patterns across host
 genotype mixtures.  These findings support the potential for
 parasites to impose negative frequency-dependent selection, while
 emphasizing that the cost of being common may vary with host genotype.
description: Data files show the raw data associated with mortality assays
 conducted following experimental selection.  
description: Data and analysis scripts for Gibson et al. 2020 An experimental
 test of parasite adaptation to common versus rare host genotypes
 Analysis file: 
 Gibson_BiolLett_Revision.rmd - contains all analyses associated
 with the paper Data files:
 CommonClone_ancestor: associated with Fig S1;
 contains ID(unique ID code), Experiment (experimental evolution project,
 either 1, AKG or 2, PSW), date of mortality assay, assayed host genotype,
 technical replicate, individual counting bodies, number of live hosts on
 mortality assay plates, total number added, number estimated to be dead,
 mortality rate, and average and SE across technical replicates
 CommonClone_homogeneous: associated with Fig S2 and Table S1 and
 text of the Supplemental Results; contains Experiment, Assay (two distinct
 assays), assay date, experimental treatment of parasite lineage, parasite
 lineage replicate number, assayed host genotype, technical replicate in
 mortality assay, individual counting bodies, number of live hosts on
 mortality assay plates, total number added, number estimated to be dead,
 and mortality rate CommonClone_dataset: focal dataset
 presented in Fig 2, Table S2, Table S3, and text of the Results and
 Supplemental Results; contains Experimenta, assay, assay date,
 experimental treatment (heterogeneous host combination in which parasite
 lineage was selected), parasite lineage replicate number, assayed host
 genotype, frequency of host genotype during experimental selection, host
 genotype that was common in experimental selection, technical replicate of
 mortality assay, individual counting bodies, number of live hosts on
 mortality assay plates, total number added, number estimated to be dead,
 mortality rate, mortality rate of ancestral parasites on assayed host
 genotype and standard error, difference between evolved mortality and
 ancestral mortality, proportional change from ancestral
 parasites CommonClone_meta: dataset for meta-analysis
 in Fig. S3 and Supplemental Results; derived from CommonClone_dataset,
 includes calculations of effect sizes