Preadult competition between colonizing populations of Drosophila subobscura and established populations of Drosophila simulans in Chile.

The palearctic species Drosophila subobscura was detected for the first time in Chile and probably in the Americas in 1978. At present, its distribution area extends between 29°54'S and 53°40'S, where it has become abundant in both domestic and wild environments, depending on the latitude and the season of the year (appearing at maximum frequency in early spring). The seasonal fluctuations of D. subobscura are the inverse of those of D. simulans, which shares the same habitat in certain regions. Under laboratory conditions D. subobscura proved to be a poor competitor during the larval developmental period in relation to D. simulans, which on the contrary seemed to be "facilitated" by the larvae of the other species. However, the existence of D. subobscura in Chile is most probably due to its population flush at a time when D. simulans is at low density.