Genetic Polymorphism – A Result of LocalAdaptation or Heterozygote Advantage?

• Stable coexistence of different self-reproducing entities requires negative frequency dependence, such that each type has an advantage when rare. In community ecology, the entities of interest are species or morphs, and negative frequency dependence arises from competition for limiting factors. In this scenario, coexistence is generally interpreted as a result of local adaptation or niche differentiation. In diploid organisms, different alleles in a specific locus can coexist if heterozygote individuals have an advantage over homozygotes. Here, at the allelic level, negative frequency dependence arises because rare alleles tend to occur in a coalition with alleles different from themselves. A classical example are MHC genes where a heterozygote advantage arises if different alleles offer protection against different sets of pathogens. Coexistence of this type can be interpreted as facilitation or division of labour. Here, we study evolution of MHC alleles in a species occurring in two habitats with different pathogen communities. Our aim is to illustrate that both types of frequency-dependent selection can drive the evolution and maintenance of allelic polymorphism, with local adaptation dominating when migration between habitats is rare and MHC alleles have close to additive effects on survival, and facilitation dominating when migration occurs frequently and alleles that offer better protection against a given pathogen community have a more than additive effect on survival.

Ämnesord

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

Nyckelord

balancing selection

heterozygote advantage

migration

patch model

MHC

Biologi med inriktning mot zooekologi

Biology with specialization in Animal Ecology

Biologi med inriktning mot zooekologi

Biology with specialization in Animal Ecology

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)