African clawed frogs (Xenopus) have been scientific and medical model species for
decades. These frogs present many curious features, and their genomic history is no
exception. As such, a variety of evolutionary genomic questions can be addressed with
these species in a comparative framework, owing to the great array of genetic tools
available and a large number of abundant species. The sex chromosomes of this group
are evolutionarily young, and this thesis establishes that there has been an additional
change in what constitutes the sex chromosomes in one species of Xenopus. This allows
us to compare the evolutionary trajectory of newly established sex chromosomes. By exploring
the genetic content of these systems, profiling their recombinational activity, and
assessing the extent of nucleotide divergence between the sex chromosomes, we find that
sex chromosome evolution may be predictable in some aspects, and highly unpredictable
in others. In addition, this genus is uncharacteristic for vertebrates in the frequency with
which lineages undergo whole genome duplication. In this thesis, we explore the selective
dynamics operating on duplicate genes over time, and the rate at which duplicate copies
are purged from the genome from multiple Xenopus species. These investigations provide
an animal perspective on the subject of biased subgenome evolution, characteristic
of allopolyploids. The last two chapters of this thesis redefine the species boundaries for
the most intensively studied Xenopus species (X. laevis), and explore the genetic extent
of hybridization between the common X. laevis and the endangered X. gilli. Overall,
this thesis provides a broad look at several aspects of Xenopus evolutionary genomics,
providing novel contributions to the fields of sex chromosome research, whole genome
duplication, and speciation and hybridization. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24130 |
| Date | January 2018 |
| Creators | Furman, Benjamin |
| Contributors | Evans, Ben, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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