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Of mice and fishes: selection and the maintenance of variation


Lindholm, Anna K. Of mice and fishes: selection and the maintenance of variation. 2015, University of Zurich, Faculty of Science.

Abstract

Understanding how trait variation is maintained within populations is important for predicting how populations will respond to environmental change. This thesis uses observational, experimental, modelling, population and quantitative genetic approaches to investigate proximate and ultimate mechanisms underlying the maintenance of variation in two species of fishes and mice. One important feature unites these four species: they can be observed and captured in the wild, and they can be kept in the laboratory and subjected to controlled experiments. The three conditions under which natural selection can maintain within-population variation were investigated: 1) variants have equal fitness, 2) selection eliminates variation but new variants are continuously generated, and 3) a balance of selective forces. Most of the work here described investigates the latter. Evidence was found for temporal fluctuation in selection in striped mice Rhabdomys pomilio (Chapter 3) and in guppies Poecilia reticulata (Chapter 8), and spatial fluctuation in selection in guppies (Chapter 7) from introduced populations (Chapter 5). We considered negative frequency-dependent selection as a mechanism to maintain rare male colour morphs in Poecilia parae (Chapter 1) and Major Histocompatibility Complex allelic variation in house mice Mus musculus domesticus (Chapter 10). Chapters 10 and 11 investigate selection at different levels at the t haplotype, which is a driving selfish genetic element in house mice. While the t haplotype has an advantage relative to the wildtype allele in transmission to the next generation, thereby experiencing positive selection, it is selected against at the level of the animal because homozygotes die prenatally. However, female heterozygotes do have a survival benefit through heterosis (Chapter 11) and Chapter 12 tests whether this survival difference between genotypes has correlated behavioural effects. Genetic tools to facilitate estimates of selection were developed in Chapter 14. Whether selection influences trait variation in the next generation depends on their proximate bases. Proximate genetic bases of trait variation were investigated in Chapters 1,2, 6 and 15 while proximate environmental bases of trait variation were considered in Chapters 3, 4, 8, 9 and 13. The combination of understanding patterns of selection and the additive genetic versus environmental contributions to trait variation are important in predicting how populations will respond to the environmental challenges of tomorrow.

Abstract

Understanding how trait variation is maintained within populations is important for predicting how populations will respond to environmental change. This thesis uses observational, experimental, modelling, population and quantitative genetic approaches to investigate proximate and ultimate mechanisms underlying the maintenance of variation in two species of fishes and mice. One important feature unites these four species: they can be observed and captured in the wild, and they can be kept in the laboratory and subjected to controlled experiments. The three conditions under which natural selection can maintain within-population variation were investigated: 1) variants have equal fitness, 2) selection eliminates variation but new variants are continuously generated, and 3) a balance of selective forces. Most of the work here described investigates the latter. Evidence was found for temporal fluctuation in selection in striped mice Rhabdomys pomilio (Chapter 3) and in guppies Poecilia reticulata (Chapter 8), and spatial fluctuation in selection in guppies (Chapter 7) from introduced populations (Chapter 5). We considered negative frequency-dependent selection as a mechanism to maintain rare male colour morphs in Poecilia parae (Chapter 1) and Major Histocompatibility Complex allelic variation in house mice Mus musculus domesticus (Chapter 10). Chapters 10 and 11 investigate selection at different levels at the t haplotype, which is a driving selfish genetic element in house mice. While the t haplotype has an advantage relative to the wildtype allele in transmission to the next generation, thereby experiencing positive selection, it is selected against at the level of the animal because homozygotes die prenatally. However, female heterozygotes do have a survival benefit through heterosis (Chapter 11) and Chapter 12 tests whether this survival difference between genotypes has correlated behavioural effects. Genetic tools to facilitate estimates of selection were developed in Chapter 14. Whether selection influences trait variation in the next generation depends on their proximate bases. Proximate genetic bases of trait variation were investigated in Chapters 1,2, 6 and 15 while proximate environmental bases of trait variation were considered in Chapters 3, 4, 8, 9 and 13. The combination of understanding patterns of selection and the additive genetic versus environmental contributions to trait variation are important in predicting how populations will respond to the environmental challenges of tomorrow.

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Additional indexing

Item Type:Habilitation
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2015
Deposited On:05 Feb 2015 15:10
Last Modified:22 Apr 2016 13:52

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