Cytosystematics of Gerbils
dc.contributor.advisor | Rambau, Ramugondo Victor | |
dc.contributor.author | Knight, Liezel Iris | |
dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. | en_ZA |
dc.date.accessioned | 2013-02-21T09:00:48Z | |
dc.date.accessioned | 2013-03-15T07:20:36Z | |
dc.date.available | 2013-02-21T09:00:48Z | |
dc.date.available | 2013-03-15T07:20:36Z | |
dc.date.issued | 2013-03 | |
dc.description | Thesis (MSc)--Stellenbosch University, 2013. | en_ZA |
dc.description.abstract | ENGLISH ABSTRACT: The objectives of this research were to: (1) accurately identify chromosome homology, (2) identify chromosome rearrangements leading to diploid number variation and chromosome evolution to formulate the ancestral gerbil karyotype and distinguish homoplasy from hemiplasy, and (3) construct a phylogeny using chromosomal characters based on G-banding and fluorescence in situ hybridization (FISH) of ten gerbil species representing five genera (Gerbilliscus, Desmodillus, Psammomys, Meriones, Taterillus), with probes derived from flow-sorted chromosomes of G. paeba (GPA, 2n = 36), and polarised with the murid outgroup, Micaelamys namaquensis. All paints successfully hybridized to all ingroup and outgroup taxa. Three of the 19 G. paeba painting probes (GPA 7, 9 and X [including the X; autosome translocation in T. pygargus]) were conserved as whole chromosomes, and 16 were rearranged (GPA 1-6, 8, 10-17). Chromosome painting correctly identified the homology of the heterochromatic GPA 7, which was conserved as whole chromosomes in all gerbils. Thirteen previously misidentified G-band homologies were correctly identified with FISH; one in D. auricularis, and six each in G. kempi and G. gambianus. Homology maps identified 57 syntenic associations and that 19 rearrangements are responsible for diploid number differentiation among species. Parsimony analysis of the two matrices (syntenic association and rearrangements) retrieved a sister-species relationship between G. gambianus and G. kempi, and P. obesus and M. persicus (syntenic associations), an unresolved clade that included D. auricularis, G. gambianus, P. obesus and M. persicus (chromosome rearrangements) and a basal position for T. pygargus. Phylogenies derived from chromosomal data failed to resolve the deeper nodes. Consequently, characters were subsequently mapped on a molecular consensus tree (including a chronogram). This allowed inferences on the rate of chromosome evolution, which indicates that the basal D. auricularis is separated from Gerbilliscus by nine rearrangements (four Robertsonian fusions, five inversions), at a rate of 1.25/Myr. Gerbilliscus species evolved with an average of 10 Robertsonian rearrangements involving GPA 1–6, 8, 10 – 12, of which four are homoplasies (GPA 1-3, 5), one a potential hemiplasy (GPA 5) to southern African taxa, one a synapomorphy to G. paeba and G. tytonis (GPA 6), two synapomorphies in G. kempi and G. gambianus (GPA 11, 12), and three are synapomorphic to Gerbilliscus (GPA 4, 8, 10). Homoplasic characters across the two clades include GPA 3 (T. pygargus, G. paeba and G. tytonis) and GPA 5p-q prox (D. auricularis, P. obesus and M. persicus). Gerbilliscus (excluding G. paeba and G. tytonis) had the slowest chromosome evolutionary rate of < 1/Myr; G. paeba and G. tytonis were slightly faster at 2/Myr. The clade comprised of M. persicus, P. obesus and T. pygargus evolved faster, at a rate of 4/Myr (seven fissions, five fusions, two inversions), 2.3/Myr (seven fissions, two fusions, four inversions) and 16/Myr (eight fusions), respectively, indicating heterogeneity among Gerbillinae: A slow rate in Desmodillus and Gerbilliscus, and a fast evolutionary rate in Psammomys, Meriones and Taterillus. The putative ancestral karyotype was postulated to be 2n = 56, and included five biarmed autosomes and X chromosome, and 22 acrocentrics. This is provisional, since Brachiones, Desmodilliscus, Pachyuromys, Sekeetamys, Gerbillus and Rhombomys were not analysed. | en_ZA |
dc.description.abstract | AFRIKAANSE OPSOMMING: Die objektief van hierdie navorsing was om: (1) akkurate chromosoom homologie te identifiseer, (2) chromosoom herranskikkings te identifiseer wat mag lei tot diploide chromosoom getal variasie en chromosoom evolusie ten einde te formuleer die voorouer karyotiepe van “gerbils” sowel as om te onderskei tussen homoplasie en hemiplasie, en (3) die konstruksie van 'n filogenetiese boomstam gebasseer op chromosoom karakters verkry vanaf G-banding en FISH (fluoressensie in situ hibridisasie) van tien “gerbil” spesies wat vyf genera verteenwoordig (Gerbilliscus, Desmodillus, Psammomys, Meriones, Taterillus), deur van geskikte sondes gebruik te maak wat verkry in deur floei-sorteerde chromosome van G. peaba (GPA, 2n = 36), wat gepolariseerd was met die Murid buitegroep, Micealamys namaquensis. Alle chromosoom verwe het suksesvolgehibridiseer aan al die ingroep en buitegroep taxa. Drie van die 19 G.peaba verfwe (GPA 7, 9 and X (including the X; autosome translocation in T. pygargus) was bewaar as heel chromosome, en 16 herrangskik (GPA 1-6, 8, 10-17). Chromosoom verfwing kon suksesvol die homologie van die heterochromatise GPA7 identifiseer wat gekonserveerd was as heel chromosome in al die “gerbils”, wat moontlik aandui die teenwoordigheid van funksionele gene. Dertien voorheen mis geidentifiseerde G-band homologieë was gekorregeer deurmiddel van FISH, een in D. auricularis, en ses elk in G. kempi en G. gambianus. Homologie kaarte het 57 sintesiese assosiasies geidentifiseer en dat 19 herrangskikings verantwoordelik was vir diploied nommer differensiasies tussen spesies. Parsimonie analises van die twee matrikse (sinteniese assosiasies en herrangskikings) wys 'n suster-spesie verwantskap tussen G. gambianus en G. kempi, en P. obesus en M .persicus (sinteniese assosiasies), 'n unopgeloste klade wat D. auricularis, G. gambianus, P. obesus en M. persicus (chromosoom herrangskikkings) opmaak vorm die basale posisie vir Taterillus pygargus. Filogenetise boomstamme verkry vanaf die chromosomale data misluk egter om die dieper nodes op te los. Karakters was daarna geplot op 'n konsensus boom (insluitend 'n chronogram). Dit het dieper insigte toegelaat soos die tempo van chromosoom evolusie, wat aandui dat die basale D. auricularis geskei is vanaf Gerbilliscus met nege herrangskikkings (vier Robertsonian, vyf inversies) teen 'n tempo van 1.25/Mja. Gerbilliscus spesies het verander met 13 herranskikinge (11 saamsmeltings en twee inversies), waarvan vier potensiele homoplasies/hemiplasies (GPA 1-3, 5). Met die uitsluitsel van G. paeba en G. tytonis, het Gerbilliscus die laagste chromosoom evolutionêre tempo van al die “gerbils” < 1 /Mja, G. paeba en G. tytonis was ietwat vinniger met 'n tempo van 2/Mja. The klade wat bestaan uit M. persicus, P. obesus en T. pygargus verander vinniger as Desmodillus en Gerbilliscus, met 'n evolutionêre tempo van 4/Mja (sewe fissies, vyf samesmeltings, twee inversies) en 2.3 Mja (sewe fissies, twee samesmeltings, vier inversies) onderskeidelik, wat grootendeels tandem was. Die karyotiepe van Taterillus pygarus het agt samesmeltings gehad wat predominant tandem was, teen 'n tempo van 16/Mja. Terwyl meeste van die herrangskikinge synapomorfies was, was sommige homoplasties of hemiplasties. Homoplastiese karakters wat gedeel was tussen die twee klades sluit in GPA 3 (in T pygargus en G. paeba en G. tytonis) en GPA 5p-q prox (D. auricularis, P. obesus en M. persicus). GPA 5 was hemiplasties aan alle suider Afrikaanse taxa. Die analise van sinteniese assosiasies en chromosoom herrangskikings was geanaliseer in PAUP, en gepolariseer met die murid Micealamys namaquensis. Taterillus pygarus het 'n basale posisie in beide filogenetiese boomstamme. Die data stel voor dat FISH meer akkurate resultate lewer op chromosoom homologie as die streng gebruik making van banding patrone. Verder het die tempo van chromosoom evolusie gevarieër vanaf stadig (Desmodillus en Gerbilliscus) tot vinnig (Psammomys, Meriones en Taterillus), chromosoom karakters egter was nie sterk genoeg om dieper filogenetiese verwantskappe te ondersoek nie. Die voornemende voorouerlike karytiepe van “gerbils” was hier gehipotiseer as 2n = 56. Drie bevindinge resoneer uit hierdie studie. Eerstens, chromosoom verwing kon chromosoom homologieë wat voorheen deur banding studies mis ge-identifiseer was korrek identifiseer: hierdie sluit in een konflik in D. auricularis, en ses elk vir G. kempi en G. gambianus. Tweedens, die homologie van die heterochromatiese of C-positiewe autosome, GPA 7, was gedemonstreer as bewaar as 'n heel chromosoom as beide heterochromaties en euchromatiese chromosome in alle “gerbils”, wat aandui dat dit functionele gene dra. Derdens gebasseer op simpleisiomorfe wat geidentifiseer was vanaf die homologie kaarte en vergelykbare opleidings, hipotiseer ek dat die voorgestelde voorouer karyotiepe bestaan uit ses autosome (GPA 7, 9, 13, 15, 16, 17) en die X chromosoom, wat onveranderd gebly het tussen alle suider Afrikaanse taxa. Met die uitsluitsel van GPA 7p/7q, was almal behoue as twee-armige chromosome in die voor ouer karyotiepe. In lyn met hierdie is, 21 akrosentries GPA1p,1q, 2p, 2q, 3p, 3q, 4p, 4q, 5p, 5q, 6p, 6q, 8p, 8q, 10q, 10p, 11p,11q, 12p, 12q en 14, wat lei tot die voorgestelde voor ouerlike diploiede chromosoom getal van 2n = 56. Diè karyotiepe word voorgestel as 'n werkende hipotese deels omdat Brachiones, Desmodilliscus, Pachyuromys, Sekeetamys, Gerbillus en Rhombomys nie geanaliseer was nie, en dat die idiale buite groep vir “gerbils” van die Acomyinae nie gebruik was om die karakters te polariseer was nie. | af_ZA |
dc.format.extent | xv, 84 p. : ill. | |
dc.identifier.uri | http://hdl.handle.net/10019.1/79821 | |
dc.language.iso | en_ZA | en_ZA |
dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
dc.rights.holder | Stellenbosch University | en_ZA |
dc.subject | Gerbillinae | en_ZA |
dc.subject | Chromosome evolution | en_ZA |
dc.subject | Chromosome painting | en_ZA |
dc.subject | Gerbilliscus paeba painting probes | en_ZA |
dc.subject | UCTD | en_ZA |
dc.subject | Theses -- Zoology | en_ZA |
dc.subject | Dissertations -- Zoology | en_ZA |
dc.title | Cytosystematics of Gerbils | en_ZA |
dc.type | Thesis | en_ZA |
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