Title:
Genetic variation in fast-evolving East African cichlid fishes: an evolutionary perspective

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dc.contributor.advisor Streelman, J. Todd
dc.contributor.advisor Yi, Soojin V.
dc.contributor.author Loh, Yong-Hwee Eddie en_US
dc.contributor.committeeMember Jordan, I. King
dc.contributor.committeeMember McDonald, John
dc.contributor.committeeMember Thomas, James
dc.contributor.department Biology en_US
dc.date.accessioned 2011-09-22T17:48:20Z
dc.date.available 2011-09-22T17:48:20Z
dc.date.issued 2011-06-23 en_US
dc.description.abstract Cichlid fishes from the East African Rift lakes Victoria, Tanganyika and Malawi represent a preeminent example of replicated and rapid evolutionary radiation. In this single natural system, numerous morphological (eg. jaw and tooth shape, color patterns, visual sensitivity), behavioral (eg. bower-building) and physiological (eg. development, neural patterning) phenotypes have emerged, much akin to a mutagenic screen. This dissertation encompasses three studies that seek to decipher the underpinnings of such rapid evolutionary diversification, investigated via the genetic variation in East African cichlids. We generated a valuable cichlid genomic resource of five low-coverage Lake Malawi cichlid genomes, from which the general properties of the genome were characterized. Nucleotide diversity of Malawi cichlids was low at 0.26%, and a sample genotyping study found that biallelic polymorphisms segregate widely throughout the Malawi species flock, making each species a mosaic of ancestrally polymorphic genomes. A second genotyping study expanded our evolutionary analysis to cover the entire East African cichlid radiation, where we found that more than 40% of single nucleotide polymorphisms (SNPs) were ancestral polymorphisms shared across multiple lakes. Bayesian analysis of genetic structure in the data supported the hypothesis that riverine species had contributed significantly to the genomes of Malawi cichlids and that Lake Malawi cichlids are not monophyletic. Both genotyping studies also identified interesting loci involved in important sensory as well as developmental pathways that were well differentiated between species and lineages. We also investigated cichlid genetic variation in relation to the evolution of microRNA regulation, and found that divergent selection on miRNA target sites may have led to differential gene expression, which contributed to the diversification of cichlid species. Overall, the patterns of cichlid genetic variation seem to be dominated by the phenomena of extensive sharing of ancestral polymorphisms. We thus believe that standing genetic variation in the form of ancestrally inherited polymorphisms, as opposed to variations arising from new mutations, provides much of the genetic diversity on which selection acts, allowing for the rapid and repeated adaptive radiation of East African cichlids. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/41148
dc.publisher Georgia Institute of Technology en_US
dc.subject Astatotilapia en_US
dc.subject Genetic differentiation en_US
dc.subject Ancestral polymorphism en_US
dc.subject Evolution en_US
dc.subject.lcsh Evolution (Biology)
dc.subject.lcsh Genetic polymorphisms
dc.subject.lcsh Genetics Research
dc.subject.lcsh Genetics
dc.title Genetic variation in fast-evolving East African cichlid fishes: an evolutionary perspective en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Streelman, J. Todd
local.contributor.corporatename College of Sciences
local.contributor.corporatename School of Biological Sciences
relation.isAdvisorOfPublication 65166986-12ce-4676-8264-b5d82ec13ae5
relation.isOrgUnitOfPublication 85042be6-2d68-4e07-b384-e1f908fae48a
relation.isOrgUnitOfPublication c8b3bd08-9989-40d3-afe3-e0ad8d5c72b5
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