Figure 1.

The distribution of ace genes in Diptera: presence (+) or absence (−) of ace-1 and ace-2 genes in the major divisions of the Diptera phylogeny. Cyclorrhapha or true flies are boxed in red and non-Cyclorrhapha in blue. Ace genes were amplified by PCR and sequenced. The gene is considered ‘absent’ when no amplification occurred after using four (for ace-1) or two (for ace-2) different pairs of primers. ‘Presence’ was always confirmed by sequencing. The number of ‘positive’ species over the total number of species sampled is given in parentheses. For Culicomorpha, data from 15 species investigated in a previous survey (Weill et al. 2002) are also included. Black circles on the phylogeny indicate monophyletic groups. When the information was available, black arrows indicate the ace gene is involved in the synthesis of the main synaptic AChE: ace-1 for five species of Culicomorpha, whereas ace-2 encodes the main synaptic AChE in two species of Schizophora Acalyptratae (Drosophila melanogaster and Bactrocera oleae) and in one species of Schizophora Calyptratae (Musca domestica). See text for explanations.