Local adaptation does not always predict high mating success.

The hypothesis that adaptation to local environments can increase mating success was tested using ten replicate lines of Drosophila melanogaster adapted either to 16 degrees C or to 25 degrees C. Competitive mating trials at both temperatures were performed with males taken from a pair of lines, one adapted to each temperature. There was no average increase in mating success for males adapted to the local environment. Although one pair of lines showed the expected pattern, another pair showed the reverse pattern. More data are needed on this hypothesis, preferably with lines that have more strongly adapted to local environments.