A cline in the Drosophila melanogaster period gene in Australia: neither down nor under

Weeks et al. (2006) have reported their inability to find a cline in the frequencies of the major Thr-Gly encoding length variant alleles of the period gene in Drosophila melanogaster in Eastern Australia. This is in contrast to a study by Sawyer et al. (2006), who found a cline on this continent from samples collected in 1993. Weeks et al. then cast doubt on the validity of a robust cline found for these variants in Europe by Costa et al. (1992), criticizing their molecular techniques and sampling methods. We show how these claims are unjustified, and reveal a number of potential problems in their own methodology. Finally by reanalysing the subset of their data which they state is more reliable, we suggest that their results from Australia may be reasonably consistent with our own.