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] |