EVOLUTION OF THE CHROMOSOMAL RACES OF MUS-MUSCULUS-DOMESTICUS IN THE RHAETIAN ALPS - THE ROLES OF WHOLE-ARM RECIPROCAL TRANSLOCATION AND ZONAL RACIATION

The evolution of ten Robertsonian (Rb) races of the house mouse (Mus m usculus domesticus) in the Rhaetian Alps of northern Italy and souther n Switzerland is reconsidered. The mechanisms of centric fusion, zonal raciation and, for the first time, whole-arm reciprocal translocation (WART), are used in this non-mathematical approach to produce a phylo genetic tree (using chromosome fusions as characters) with the smalles t number of steps. The shortest tree that we found (16 steps) is at le ast two to nine mutations shorter than previously published models. Th ree other trees (17 or 18 steps) are also considered, since they are g eographically more sensible. In general, these four scenarios correspo nd more closely to the present distributions of the ten Rb races than previous trees. Our results suggest that zonal raciation and WARTs pla y an important role in the evolution of Rb races of the house mouse. ( C) 1997 The Linnean Society of London.