Chromosomal evolution of the house mouse, Mus musculus domesticus, in the Aeolian Archipelago (Sicily, Italy)

We describe the chromosomal evolution of the metacentric populations of the house mouse, Mus musculus domesticus, which constitute the Robertsonian System of Aeolian Islands (Sicily, Italy). Eighty-nine specimens from all the seven islands that form the Archipelago were cytogenetically examined. The analysis shows the presence of 4 Rb races with a large number of shared metacentric chromosomes: 2n = 36 on Panarea, 2n = 34 on Alicudi, 2n = 26 on Lipari and Stromboli, and a different 2n = 26 race on Vulcano. On Salina and Filicudi, the standard karyotype was found. Polymorphism was only found in a population on Panarea Island and this population shares no metacentrics with the other races. The distribution of metacentrics among the races and the comparison between the Aeolian metacentrics and those found in the 97 previously documented metacentric populations allows us to formulate a hypothesis of chromosomal evolution for the Aeolian Robertsonian system. Six of the twelve metacentric chromosomes found in the Aeolian Islands come from localities outside the archipelago. The evolutionary model highlights how the chromosomal races originated inside the Archipelago and involve several factors, such as formation in situ of metacentrics, zonal raciation and, whole arm reciprocal translocation. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 194-202.