SOMATIC ACTIVITY OF THE MARINER TRANSPOSABLE ELEMENT IN NATURAL-POPULATIONS OF DROSOPHILA-SIMULANS

The characteristics of the mariner transposable element in natural pop ulations of Drosophila simulans from different parts of the world were analysed. The somatic excision rate (estimated from a test-cross with a reference strain), the average number of copies (determined by Sout hern blots), and the presence of deleted copies (detected by polymeras e chain reaction amplification) were estimated for each population. Th ere was a great variability in the somatic excision rate, measured as the percentage of mosaic males, both within and between populations. T he population effect was highly significant. The average copy number a lso varied widely and was correlated with the excision rate. Rare dele ted elements were detected by polymerase chain reaction and Southern b lots. Percentage of mosaic males increased in strains kept for a long time at low temperature, and the somatic excision rate increased with the latitude of origin of populations. Therefore, these results strong ly suggest that temperature could be involved in the regulation of mar iner somatic excision in D, simulans.