Fig. 3. Most parsimonious TCS network depicting the relationships among ORN response patterns to the 11 tested fruit volatile compounds (see Fig. 2) for (A) parental apple, hawthorn and dogwood flies, and (B) F₁ hybrids. Each oval node represents a different response pattern observed in the parent or hybrid neuron population, with numbers above or below nodes indicating the ORN response profile according to the numbered compounds listed in Fig. 2. The five black nodes at the top of each diagram designate the five general response categories identified in the parent population. These response categories are similar to the cluster analysis classes (Olsson et al., 2006a) (Table 2) listed above each node. The sizes of oval nodes reflect the relative proportions of the different neural response patterns observed in the test population (N=77 neurons recorded for parents, N=118 for F₁ hybrids), with black nodes indicating shared response patterns seen in both parents and hybrids and white nodes unique response patterns. Furthermore, white labeled nodes represent neurons responding to only the respective compound shown (mono-response patterns). Shared neurons (black nodes) are anchored in the same positions in A and B to provide reference points for comparing the parent and hybrid networks, and are labeled by their response pattern. The number of straight-line segments connecting two nodes indicate the difference in the number of compounds that the neurons responded to. Compounds 7 and 8 (pentyl hexanoate and butyl hexanoate) were considered to represent a single volatile for network construction and branch length calculation owing to the high positive correlation in neuron response between the two compounds.