Thesis (PhD (Botany and Zoology)) -- University of Stellenbosch, 2008. / Afrosoricida is a 65 million years old (my) eutherian order that together with the
Tubulidentata (aardvark) and Macroscelidea (elephant shrews) form the
Afroinsectiphillia, a subclade of Afrotheria. It includes two families – Chrysochloridae
(nine genera of golden moles) and Tenrecidae (11 genera of tenrecs) – that collectively
represent ~59% of the afrotherian generic diversity. This study presents the first
comprehensive cytogenetic comparison between members of these two families (seven
genera and 11 species/subspecies of golden moles, and two genera and 11 species of
tenrecs) using G- and C-banding and chromosome painting. All detected
rearrangements are interpreted in a strict cladistic framework. In the case of
Chrysochloridae, this provides evidence for a sister relationship between Chrysochloris
and Cryptochloris, the monophyly of the Amblysomus genus, and for the elevation of A.
hottentotus meesteri to specific rank. The detection of telomeric-like repeats in the
centromeres of all chromosomes of the Amblysomus species/subspecies but not in those
of A. h. meesteri further strengthens its recognition as a distinct species. Parsimony
analysis of chromosomal rearrangements within Tenrecidae, the second Afrotheria
assemblage studied, showed that rearrangements which could be interpreted as Whole
Arm Reciprocal Translocations (WARTs) were more likely to be the result of
Robertsonian translocations. Four interspecific associations are recovered within
Microgale that are consistent with morphological and molecular characters. It was also
possible to infer ancestral karyotypes for the Chrysochloridae, Oryzorictinae and the
two tenrecid genera, Oryzorictes and Microgale. Given the relatively high karyotypic
diversity observed among some Microgale species and the prevailing debates on
chromosomal evolution and regional palaeoenvironmental fluctuations, it is suggested
that Microgale be added to the list of taxa where structural rearrangements are likely to
have played a role in speciation. Using Genbank sequences and a relaxed Bayesian
clock method, we estimate the age of the family Chrysochloridae at ~28.5 my and that
of the genus Microgale at ~9.9 my. Based on these dates, it can be shown that most of
the evolutionary branches are characterized by a slow rate of chromosomal change, but
that markedly high rates are observed in some Microgale species and to a lesser extent
in the lineage leading to A. robustus. The rates of chromosomal evolution and other
cytogenetic features highlighted in this study are discussed in light of recent advances in
understanding the molecular mechanims that underpin changes to genomic architecture.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1169 |
| Date | 03 1900 |
| Creators | Gilbert, Clement |
| Contributors | Robinson, T. J., Hassanin, A., University of Stellenbosch. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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