On the category of naturally occurring inversions of Drosophila melanogaster

The categorization of naturally occurring inversions in Drosophila melanogaster made by Mettler et al. (1977) was re-examined through compilation of recent data from the world-wide investigations. Categorization was changed into 5 classes by adding a new class: Common cosmopolitan, Rare cosmopolitan, Quasi cosmopolitan, Endemic and Unique. Modifications were also proposed: (1) The Rare cosmopolitans were limited to the 3 inversions, In(3L)M, In(3R)C and In(3R)Mo, instead of 8 inversions originally included. (2) Ambiguity between Endemic and Unique was noted and discussed. Data were presented to show that repeated surveys of the usual scale in a natural population indeed detected Endemic inversions which otherwise would have been classified as Unique inversions. More recent data on Japanese natural populations were finally presented. The Common cosmopolitans but not the Rare and Quasi cosmopolitans clearly showed high frequencies in the south.