DOI: 10.5061/dryad.8sf7m0ckb
title: The cost of travel: how dispersal ability limits local adaptation in host-parasite interactions

description: Classical theory suggests that parasites will exhibit higher fitness in
 sympatric relative to allopatric host populations (local adaptation).
 However, evidence for local adaptation in natural host-parasite systems is
 often equivocal, emphasizing the need for cross-infection experiments
 conducted over realistic geographic scales and comparisons among species
 with varied life history traits. Here, we conducted cross-infection
 experiments to test how two trematode (flatworm) species (Paralechriorchis
 syntomentera and Ribeiroia ondatrae) with differing dispersal abilities
 varied in the strength of local adaptation to their amphibian hosts. By
 pairing 26 host-by-parasite population cross-infections from across the
 western USA with analyses of host and parasite spatial genetic structure,
 we found that increasing geographic distance – and corresponding increases
 in host population genetic distance – reduced infection success for P.
 syntomentera, which is dispersed by snake definitive hosts. For the
 avian-dispersed R. ondatrae, in contrast, the geographic distance between
 the parasite and host populations had no influence on infection success.
 Differences in local adaptation corresponded to parasite genetic
 structure; while populations of P. syntomentera exhibited ~10% mtDNA
 sequence divergence, those of R. ondatrae were nearly identical
 (&lt;0.5%), even across a 900 km range. Taken together, these results
 offer empirical evidence that high levels of dispersal can limit
 opportunities for parasites to adapt to local host populations.
description: pseudacris_regilla_fastqs<br> Directory containing .fastq
 files for all <em>Pseudacris regilla </em>individuals analyzed
 in the paper. This directory has been compressed as a tar archive. To
 uncompress from the command line:$ tar -zxvf
 pseudacris_regilla_fastqs.tar.gz
 pseudacris_regilla_specimen_information
 This text file contains information on each Pseudacris regilla
 specimen analyzed with GBS data.  This file contains identification
 numbers for voucher specimens and their corresponding barcode
 identification.  
 Experimental_Crosses_AllSpp This .csv
 file contains data on experimental infections between hosts
 (<i>Pseudacris regilla </i>“PSRE") and parasites
 (<i>R. ondatrae </i>“Rib”, <i>P.
 syntomentera </i>“Mano”) collected from different source
 populations.  
 Experimental_Crosses_PSRE This .csv file
 contains data on experimental infections between multiple species of
 amphibian hosts (<i>P. regilla </i>“PSRE",
 <i>A. Boreas </i>“BUBO”, <i>T. torosa </i>“TATO”)
 and the parasite <i>R. ondatrae </i>collected from different source
 populations.  
 Geog_Dist This .csv file pairwise
 geographic distance (in km) between locations where <i>P. regilla
 </i>individuals
 were sampled and sequenced. 
   MeanFST_frog
 Pairwise FST between populations of <i>P.
 regilla</i>  
 neisD_frog pairwise genetic distance (as
 Nei’s D) between populations of <i>P. regilla </i>
  
 Parasite_Genetic_Dist pairwise genetic
 distance (as base pair sequence similarity) between
 parasite<i> </i>samples collected from multiple
 locations, for both <i>R. ondatrae </i>“Rib” and
 <i>P. syntomentera “</i>Mano”. 
   PSRE_PCA_scores
 PCA scores
 from <i>P. regilla </i>individuals used in experimental
 crosses, derived from SNP analysis 
   Johnson_ParasiteDispersal_Analysis code for reproducing the statistical analyses (GLMMs) and figures from the paper.