A genetic and geographic study of IPI courtship song in Drosophila melanogaster

In Drosophila melanogaster, the male produces a song during courtship which is characterised by interpulse intervals, (IPIs), which oscillate around a mean of 30-40 ms. The song characteristics of Australian population of D. melanogaster collected from various latitudes were studied. Because a wide variation of IPI was noted, a selection protocol was performed on single isofemale lines. Males producing long or short IPI's were mated to related females, resulting in two lines of flies singing with long and short IPI means. The selected lines were stored for 32 months without further selection. Regular sampling of these lines showed that the IPI difference was maintained.;To understand the genetics of IPI, the long and short lines were mated together. The long line was also mated to a line of Kenyan lines which was found to sing with an unusually short IPI. Analysis of the results showed that although father-son realized heritability was low, there were significant autosomal dominance effects which together reduced IPI by 2-3 ms. Competitive mating tests were undertaken. D. melanogaster had a preference for males producing long song. However it was noted that the long IPI males had larger body size.;A screening programme of the Australian flies was undertaken to study the relationship between IPI, body size, latitude and altitude. James et al. (1993) had demonstrated a correlation between latitude and body size. This was confirmed by these experiments, with larger flies existing in cooler latitudes. There was also a correlation between IPI and latitude, with flies from higher latitudes singing with longer IPIs. There was no significant correlation between IPI and body size, or IPI and altitude. The search for IPI variants was extended to include flies from Israel and Kenya. The implications of microhabitats and local environments are also discussed.