VARIATION IN GENE FREQUENCIES IN RODENT POPULATIONS: THE ROLES OF SELECTIVE AND NONSELECTIVE EVOLUTIONARY FORCES

Persistent Link:
http://hdl.handle.net/10150/290564
Title:
VARIATION IN GENE FREQUENCIES IN RODENT POPULATIONS: THE ROLES OF SELECTIVE AND NONSELECTIVE EVOLUTIONARY FORCES
Author:
Whittam, Thomas Stewart
Issue Date:
1981
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The study of protein polymorphism in natural populations has stimulated heated controversy over the effects of various evolutionary forces on the observed patterns of genetic variation. One viewpoint is that a majority of the mutations at a locus are selectively equivalent and that variations in gene frequencies in time and space are primarily a result of nonselective evolutionary forces. The opposing view is that most mutations have sufficient effect on individual fitness that variations in gene frequencies are adaptations resulting from the action of natural selection. I compared gene frequency distributions among various loci to assess the roles of selective and nonselective evolutionary forces in determining patterns of allozyme variation in populations of rodents. I used two versions of the Lewontin-Krakauer test on temporal variation in allozyme frequencies reported for populations of the prairie vole, Microtus ochrogaster. The tests revealed that the changes in gene frequency were homogeneous among loci which suggests that nonselective forces such as genetic drift and migration were the primary cause of gene frequency change within populations. I also compared the spatial gene frequency distributions reported for 17 species of rodents to assess which evolutionary factors account for the genetic differentiation of populations within each species. Most loci showed similar degrees of differentiation, a pattern expected if nonselective forces operated in population differentiation. I found a positive relationship between the amount of differentiation of populations and the magnitude of positive association among rare alleles. This result suggests an active role of genetic drift in population differentiation within rodent species. The analysis of allozyme distributions in populations of rodents indicates that nonselective evolutionary forces play a substantial role in determining patterns of genetic variation. According to Wright's Shifting Balance Theory, the random differentiation of populations may actually accelerate adaptive evolution, which may account for the rapid evolutionary rates found in rodents.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Gene frequency.; Rodents -- Genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Ecology and Evolutionary Biology
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleVARIATION IN GENE FREQUENCIES IN RODENT POPULATIONS: THE ROLES OF SELECTIVE AND NONSELECTIVE EVOLUTIONARY FORCESen_US
dc.creatorWhittam, Thomas Stewarten_US
dc.contributor.authorWhittam, Thomas Stewarten_US
dc.date.issued1981en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe study of protein polymorphism in natural populations has stimulated heated controversy over the effects of various evolutionary forces on the observed patterns of genetic variation. One viewpoint is that a majority of the mutations at a locus are selectively equivalent and that variations in gene frequencies in time and space are primarily a result of nonselective evolutionary forces. The opposing view is that most mutations have sufficient effect on individual fitness that variations in gene frequencies are adaptations resulting from the action of natural selection. I compared gene frequency distributions among various loci to assess the roles of selective and nonselective evolutionary forces in determining patterns of allozyme variation in populations of rodents. I used two versions of the Lewontin-Krakauer test on temporal variation in allozyme frequencies reported for populations of the prairie vole, Microtus ochrogaster. The tests revealed that the changes in gene frequency were homogeneous among loci which suggests that nonselective forces such as genetic drift and migration were the primary cause of gene frequency change within populations. I also compared the spatial gene frequency distributions reported for 17 species of rodents to assess which evolutionary factors account for the genetic differentiation of populations within each species. Most loci showed similar degrees of differentiation, a pattern expected if nonselective forces operated in population differentiation. I found a positive relationship between the amount of differentiation of populations and the magnitude of positive association among rare alleles. This result suggests an active role of genetic drift in population differentiation within rodent species. The analysis of allozyme distributions in populations of rodents indicates that nonselective evolutionary forces play a substantial role in determining patterns of genetic variation. According to Wright's Shifting Balance Theory, the random differentiation of populations may actually accelerate adaptive evolution, which may account for the rapid evolutionary rates found in rodents.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGene frequency.en_US
dc.subjectRodents -- Genetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8129343en_US
dc.identifier.oclc8278468en_US
dc.identifier.bibrecord.b18055059en_US
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