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Three morphological datasets (traditional measurements, dorsal and ventral skull shape coordinates) were used to examine craniometric variation in the water rat

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This study examines inter-population variation in the subspecies of water rat Dasymys incomtus in eastern and extreme southwestern South Africa. Dasymys incomtus is widespread but its distribution is limited to water sources. Two techniques, protein electrophoresis and traditional cranial morphometrics, were used to investigate South African D. /. incomtus populations with known differences in chromosome numbers (2n = 38 from the KwaZulu-Natal and 2n = 46 from the Northern Province). Both electrophoretic and morphometric data confirmed the cytogenetic results, with specimens from the Northern Province forming one group and specimens from the KwaZulu-Natal forming another. A high F CT value (0.424), low Nm value (0.068) and the presence of three fixed alleles (Aspartate Aminotransferase-1, Glycerol-3-phosphate and Purine-nucleoside) across the populations indicated the genetic separation of the KwaZulu-Natal and Northern Province localities. Morphological separation between the populations occurred in five cranial characters: condylobasal length, palatal length, greatest mandible length, incisor to condyle length and ZAE, as evidenced by their high F-values and their high loadings on the first principal component. Carson's population flush theory, Wright's isolation by distance theory and the role of paleoclimates in conjunction with habitat constraints on population movement were considered as possible explanations for the patterns seen in this study.Resume. -Cette e*tude a permis d'examiner des variations entre populations du rat d'eau Dasymys incomtus. Les individus appartenant a cette espece sont tres ropandus en Afrique mais ont une ^partition qui se limite aux zones humides. Deux techniques, Felectrophorese des proteines et la morphomotrie classique cränienne ont £te utilises pour examiner d'eVentuelles differences entre des specimens pr&entant des nombres chromosomiques distincts selon Gordon (1991) (2n = 38 pour la sous-espece du KwaZulu-Natal et 2n = 46 pour celle de la Northern Province). D'une maniere g£n6rale, les donne*es d'ölectrophorese et de morphometrie confirment les r£sultats cytt^notiques, les specimens de la Northern Province formant un groupe, ceux du KwaZulu-Natal un autre. Une valeur F^ haute (0.424), une valeur Nm basse (0.068) et la prosence de trois alleles fixes (AAT -1, GDP et PNP) dans les populations ont montro une sopara- Mammalia, t. 66, n° 3, 2002 : 381-404. Brought to you by | University of Georgia Libraries Authenticated Download Date | 5/30/15 10:35 PM 382 MAMMALIA tion genetique des localites du KwaZulu-Natal et de la Northern Province. Au niveau morphologique, ces deux populations se distinguent par cinq caracteres craniens: CBL, PAL, GML, ITC et ZAE, grace ä leurs hautes valeurs de F et leurs poids £leves sur le premier axe de Fanalyse en composantes principales. La throne de "flush" de population de Carson, la theorie d'isolement par la distance de Wright et le role des paleoclimats en liaison avec les contraintes d'habitat sur les mouvements de population, ont ete consi...