Sexual selection and incipient speciation in Hawaiian Drosophila

Abstract

We conducted sexual selection experiments to produce strains with high and low mating discrimination in females of laboratory strains of Hawaiian Drosophila, D. silvestris, then examined secondary sexual traits of these two lines, and compared them with that of standard line. In order to do this, we screened out super-males which mated successfully with females and with high mating records; and poor males which usually could not mate successfully with females and had low mating records. In the meantime, choosy females were also screened out, which almost never responded to males’ nuptial dance and were difficult to be mated; but indiscriminate females were on the contrary, which were very ready to accept male’s nuptial dance and were very easy to be mated. As a result, by mating super-males with choosy females, we were able to produce the high-line strain; similarly, for the low line, we mated poor males with indiscriminate females and we had a strain that was significantly different from our standard strain within just two generations of selection, i.e., morphological trait differences were measured between the standard strain and the two selected lines, which indicated that mating discrimination has affected secondary sexual traits of the low-line strain significantly: Cilia number on the foretibia of low-line males is significantly different from that of the standard line, which perhaps was the indication of incipient speciation in Hawaiian Drosophila.