Pathogens as Causes of Genetic Diversity in their Host Populations

Hamilton, W. D.

doi:10.1007/978-3-642-68635-1_14

Cited by 207 publications

(149 citation statements)

References 54 publications

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“…Based on previous theoretical work [9], we expected that parasite-mediated frequency-dependent selection should play a role in the maintenance of genetic diversity among ®sh species. In other words, we expected ®sh species exposed to a wide range of parasite species to display higher levels of heterozygosity and/or polymorphism because such species are subject to a greater variety of selection pressures.…”

Section: Discussionmentioning

confidence: 99%

“…A possible mechanism widely discussed in recent years is that parasites and pathogens exert frequencydependent selection on their hosts, favouring rare host alleles that may confer greater resistance against widespread parasites [9]. Indeed, genetic resistance against parasites quickly becomes obsolete as parasites evolve at higher rates than their hosts.…”

Section: Introductionmentioning

confidence: 99%

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Metazoan parasite species richness and genetic variation among freshwater fish species: cause or consequence?

Poulin

Marshall

Spencer

2000

International Journal for Parasitology

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The factors responsible for the maintenance of genetic variation among natural populations remain a mystery. Recent models of host±parasite co-evolution assume that parasites exert frequency-dependent selection on their hosts by favouring rare alleles that may confer resistance against infection. We tested this prediction in a comparative analysis that sought relationships between levels of genetic variation and the number of metazoan parasite species exploiting each host species. We used data on 40 species of North American freshwater ®shes. After controlling for sampling e ort and phylogenetic in¯uences, we found no relationship between genetic polymorphism and parasite species richness among ®sh species. However, we found a marginal negative correlation between parasite species richness and heterozygosity. This result goes against the prediction that increased selective pressure by parasites should be associated with higher levels of genetic variation. Instead, it suggests that parasites may be colonising host species showing low levels of genetic variation with greater success than genetically more variable host species. 7

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metazoan parasite species richness and genetic variation among freshwater fish species: cause or consequence?

Poulin

Marshall

Spencer

2000

International Journal for Parasitology

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“…For instance, photosynthesis genes encoded by both cyanobacteria and their infecting viruses appear to have undergone repeated recombination events (8,9). Second, viruses, like other pathogens, are thought to maintain host diversity by frequency dependence such that host strains (genotypes or taxa) that become relatively abundant are more susceptible to attack (the "kill the winner" hypothesis) (10)(11)(12). Finally, viruses might affect marine host diversity by promoting the emergence of viral resistance, leading to antagonistic coevolution (the reciprocal evolution of host resistance and viral infectivity) (13).…”

mentioning

confidence: 99%

Rapid diversification of coevolving marine Synechococcus and a virus

Marston

Pierciey

Shepard

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

179

177

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Marine viruses impose a heavy mortality on their host bacteria, whereas at the same time the degree of viral resistance in marine bacteria appears to be high. Antagonistic coevolution-the reciprocal evolutionary change of interacting species-might reconcile these observations, if it leads to rapid and dynamic levels of viral resistance. Here we demonstrate the potential for extensive antagonistic coevolution between the ecologically important marine cyanobacterium Synechococcus and a lytic virus. In a 6-mo-long replicated chemostat experiment, Synechococcus sp. WH7803 and the virus (RIM8) underwent multiple coevolutionary cycles, leading to the rapid diversification of both host and virus. Over the course of the experiment, we detected between 4 and 13 newly evolved viral phenotypes (differing in host range) and between 4 and 11 newly evolved Synechococcus phenotypes (differing in viral resistance) in each chemostat. Genomic analysis of isolates identified several candidate genes in both the host and virus that might influence their interactions. Notably, none of the viral candidates were tail fiber genes, thought to be the primary determinants of host range in tailed bacteriophages, highlighting the difficulty in generalizing results from bacteriophage infecting γ-Proteobacteria. Finally, we show that pairwise virus-host coevolution may have broader community consequences; coevolution in the chemostat altered the sensitivity of Synechoccocus to a diverse suite of viruses, as well as the virus' ability to infect additional Synechococcus strains. Our results indicate that rapid coevolution may contribute to the generation and maintenance of Synechococcus and virus diversity and thereby influence viral-mediated mortality of these key marine bacteria.cyanophage | bacterial diversity | arms race

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“…We have observed a heterozygote excess at the microsatellite locus OPA CAP which may reflect overdominant mechanisms. With the involvement of nematode and possibly other parasites in crash survival (Gulland, 1992;Gulland et a!., 1993) a third possibility is that genetic variation in Soay sheep is associated with changes in parasite genotypes (Hamilton, 1982). Finally, of course any combination of these factors may be occurring simultaneously within our population.…”

Section: Discussion Level Of Protein Variationmentioning

confidence: 98%

Extensive protein and microsatellite variability in an isolated, cyclic ungulate population

1995

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We investigated polymorphism at protein and microsatellite DNA loci in an isolated, umnanaged and cyclic population of Soay sheep on the island of Hirta, St. Kilda. Extensive molecular variation was revealed at both protein loci (mean heterozygosity 7.78 per cent) and microsatellite loci (mean heterozygosity 50.93 per cent). Typically, large mammals possess limited protein variation and we were surprised to observe such a level of protein heterozygosity, particularly considering the genetic history of the Hirta population. Indeed, compared to other mammals, Soay sheep lie within the top 17 per cent of the distribution of average protein heterozygosities. We discuss the level of protein heterozygosity in the context of other mammalian species, other breeds of sheep and the genetic history of Soay sheep. Possible explanations for a large average and interlocus variance in protein heterozygosity are proposed. Although little data are available from other studies to compare with microsatellite DNA variability in this population, we discuss the potential application of microsatellite markers to interpopulation and interspecific genetic studies.

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Pathogens as Causes of Genetic Diversity in their Host Populations

Cited by 207 publications

References 54 publications

Metazoan parasite species richness and genetic variation among freshwater fish species: cause or consequence?

Metazoan parasite species richness and genetic variation among freshwater fish species: cause or consequence?

Rapid diversification of coevolving marine Synechococcus and a virus

Extensive protein and microsatellite variability in an isolated, cyclic ungulate population

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