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Table 1 Evidence for pathogen-driven selection mechanisms in free-ranging vertebrate populations investigated in their natural environment.

From: The importance of immune gene variability (MHC) in evolutionary ecology and conservation

Host species Host environment Country Infectious agent Heterozygote advantage Negative frequency-dependent selection Reference
Three-spined stickleback
(Gasterosteus aculeatus)
Lakes and rivers Germany 14 species of macroparasites Supported in terms of a general diversity advantage; minimal parasitation at intermediate MHC class IIB diversity; population exposed to more diverse parasites had more different alleles. Not investigated [47]
Soay sheep
(Ovis aries)
Large unmanaged population on an island Scotland Strongyle nematode Not supported; heterozygosity is not the critical factor determining mortality in lambs and yearlings. Common alleles (OLADRB 205, OLADRB 257) were associated with decreased lamb or yearling survivorship and a high incidence of parasitism; the rarer allele (OLADRB 263) with increased yearling survival. [56]
Gray mouse lemur
(Microcebus murinus)
Littoral rain forest Madagascar Seventeen nematode species; separate data analysis for (most common) single and multiple infections. Not supported; heterozygosity was uncorrelated with infection status (being infected or not), the number of different nematodes per individual (NNI) as well as with the faecal egg counts (FEC, eggs/g faeces). The common allele Mimu-DRB*1 was more frequently found in infected individuals, in individuals with high number of different nematode species infections (NNI) and faecal egg counts (FEC); the rare alleles Mimu-DRB*6 and 10 were more prevalent in not infected individuals and in individuals with low NNI and FEC values. [174]
Yellow-necked mouse
(Apodemus flavicollis)
Tree-dominated habitat Germany Eight nematode species; separate data analysis for (most common) single and multiple infections. Not supported; heterozygosity did neither influence the infection status (being infected or not), nor the number of different nematode infections (NNI) nor the individual faecal egg count (FEC, eggs/g faeces) values. Mice carrying allele Apfl-DRB*5 or the closely related allele Apfl-DRB*15 had an increased risk of being nematode infected and displayed higher FEC than individuals carrying other alleles; the allele Apfl-DRB*23 was associated with low FEC in separate analyses of the most common nematode. [173]
Hairy-footed gerbil
(Gerbillurus paeba)
Dunefield of the Southern Kalahari Desert South Africa Two different cestode species, six different nematode species Not investigated Gepa-DRB*15 was only found in not infected mice. [172]
Striped mouse
(Rhabdomys pumilio)
Dunefield of the Southern Kalahari Desert South Africa Eight different nematode species Supported; heterozygosity did influence the infection status (being infected or not) and the individual faecal egg count (FEC) value with higher values observed in homozygous individuals. The allele Rhpu-DRB*1 occurred more frequently in infected individuals and in individuals with high FEC values (high parasite load). In contrary, the allele Rhpu-DRB*8 occurred more often in individuals with low FEC values. [163]