Remating, sperm transfer, and sperm displacement in the cactophilic species Drosophila buzzatii Patterson & Wheeler (Diptera : Drosophilidae)

The mating system of Drosophila buzzatii is characterized by short copulati on duration, frequent remating in both males and females, and male ejaculat e partitioning. Additional features of the system are strong sperm displace ment and a high frequency of sterile matings. Remating frequencies and the effects of remating on various mating parameters were studied. In order to characterize variation, five isofemale lines from geographically distant lo calities in Australia (three localities), Brazil and the Canary Islands wer e used. Mating parameters studied were: premating time, copulation duration , interval between successive matings, and progeny number as a measure of s perm transfer. Variation for sperm displacement was studied in crosses betw een laboratory stocks and a number of isofemale lines from Australia. There were significant between-line differences in female remating frequencies, premating time, copulation duration, interval between successive matings, a nd progeny numbers, indicating genetic Variation for these traits. Females from the five lines mated on average 1.6 to 3.1 times in 4 h, with a maximu m of eight matings for one female. The males were given a maximum of ten vi rgin females in sequence and more than one-third of the males mated all ten females in the 2h observation period. Copulation duration decreased and in terval between matings increased with copulation number in multiply mated m ales. Mean copulation duration was c. 2 min. Sperm transfer, measured as th e average number of progeny from a single mating, was low (c.25) and multip ly mated females gave more progeny than single mated females, although with much lower progeny numbers than observed in wild-caught non-virgin females . A surprisingly high proportion of observed matings gave no progeny, i.e. they were sterile matings. Sperm displacement was strong in most crosses an d remained strong in multiply mated females. The results are discussed in r elation to the evolution of mating patterns in Drosophila. (C) 2000 The Lin nean Society of London.