DOI: 10.5061/dryad.456f3
title: Data from: Selection from parasites favors immunogenetic diversity but not divergence among locally adapted host populations

description: The unprecedented polymorphism in the major histocompatibility complex
 (MHC) genes is thought to be maintained by balancing selection from
 parasites. However, do parasites also drive divergence at MHC loci between
 host populations, or do the effects of balancing selection maintain
 similarities among populations? We examined MHC variation in populations
 of the livebearing fish Poecilia mexicana and characterized their parasite
 communities. Poecilia mexicana populations in the Cueva del Azufre system
 are locally adapted to darkness and the presence of toxic hydrogen
 sulfide, and represent highly divergent ecotypes or incipient species.
 Parasite communities differed significantly across populations, and
 populations with higher parasite loads had higher levels of diversity at
 class II MHC genes. However, despite different parasite communities,
 marked divergence in adaptive traits and in neutral genetic markers, we
 found MHC alleles to be remarkably similar among host populations. Our
 findings indicate that balancing selection from parasites maintains
 immunogenetic diversity of hosts, but this process does not promote MHC
 divergence in this system. On the contrary, we suggest that balancing
 selection on immunogenetic loci may outweigh divergent selection causing
 divergence, thereby hindering host divergence and speciation. Our findings
 support the hypothesis that balancing selection maintains MHC similarities
 among lineages during and after speciation (trans-species evolution).
description: 1 Parasite
 communitiesThis file includes the
 raw data about the occurrence of parasites across 6 sites investigated in
 the study. Included are data for individual hosts and counts of specific
 parasites as outlined in the paper. Variables include an individual
 identification number (which is also used for the MHC and microsatellite
 data), population of origin for each host individual, sex, standard length
 (in millimeter), as well as the number of Oodinium, Ambiphyra, Trichodina,
 Dactylogyrus, Gyrodactylus, Diplostomum cf. spathaceum, Echinochasmus cf.
 donaldsoni, Uvulifer, Trematode 1, Trematode 2, Trematode 3, Nematode,
 Cestode, and Lernea recorded per host.2 Microsatellite
 haplotypesThis file includes the
 raw microsatellite data of hosts investigated across 6 sites. Variables
 include an individual identification number, population of origin for each
 host individual, and allele lengths for 12 microsatellite loci of each
 individual host. Sequence data is available through
 Genbank.3 MHC
 haplotypesThis file includes the
 raw data on MHC IIB haplotypes of hosts investigated across 6 sites.
 Variables include an individual identification number, population of
 origin for each host individual, the total number of MHC IIB alleles per
 individual, and individual-level presence or absence information for all
 81 alleles documented in the study. Sequence data is available through
 Genbank.4 BSD temporal
 variationRaw data of the presence
 of black spot disease (BSD; Uvulifer sp.) across a temporal series of
 samples from all 6 population investigated in this study. Variables
 included are year of collection, habitat type, population of origin, as
 well as the number of Uvulifer cysts and the presence or absence of
 Uvulifer cysts. Note that data is not available for all populations and
 all years (see main manuscript) and that only presence/absence data was
 available for some years.Fasta Genbank 80 MHC
 haplotypesThis fasta file contains
 the DNA sequences of the 80 unique MHC Class IIB alleles that were
 isolated in this study. Each of our six subpopulations have different
 combinations of these alleles.