GENETIC DIFFERENTIATION AND HABITAT PARTITION OF ROBERTSONIAN HOUSE MOUSE-POPULATIONS (MUS-MUSCULUS-DOMESTICUS) OF TUNISIA

The karyological analysis of Tunisian populations of house mice revealed the existence of a Robertsonian (Rb) chromosomal race carrying nine pairs of metacentric chromosomes in central Tunisia. Divergence estimates showed that they are genetically differentiated from local all-acrocentric populations and have a reduced level of genic variability. The Rb populations are restricted to urban habitats, whereas all-acrocentric populations occur in rural areas. Contact zones between these two types of habitat yield chromosomally polymorphic populations. Analysis of gene flow indicates that it is reduced and limited to populations bordering the contact areas. The reduced genic variability and patchy distribution exhibited by the Tunisian Rb mice do not agree with results from previous studies of the European Rb populations. Two hypotheses are presented to account for this discrepancy based on local differentiation versus introduction of the Tunisian Rb race.