Host-plant chemicals and distribution of Neuquenaphis on Nothofagus

Extractable metabolites from leaves (EM) and volatiles released from six No thofagus species were analyzed by TLC and GC-MS, respectively. Aphids of th e genus Neuquenaphis, closely associated to Nothofagus, were sampled on eac h Nathofagus species. Cluster analyses of Nothofagus species were performed based on the presence or absence of EM and volatiles. Dissimilarity distan ces, from the cluster analyses of EM and volatiles, were used to evaluate t heir association with the aphid distribution. A major component identified from EM and volatiles of three species of Nothofagus, alpha-agarofuran, was attractive to alates of the oligophagous Neuquenaphis sensoriata, which us e them as hosts. These results suggest that chemicals play a significant ro le in the host-plant associations between Neuquenaphis and Nothofagus.