Specimens of the leafhopper genus Balacha were studied from Argentina, Brazil, Paraguay, and Uruguay. Colombia appears to be an erroneous record for the genus. The analysis of 18 taxa and 67 morphological characters showed that Balacha is a monophyletic assemblage comprising two major lineages: the red Balacha clade including B. lepida (B. distincta + B. rubripennis), and the black Balacha clade including Balacha sp. nov. (B. decorata (B. melanocephala + B. similis). In spite of the scarcity of information on host-plant usage of outgroup taxa (probably generalists on Lamiaceae, Lauraceae, and Asteraceae), we believe that the shift to feeding on Eryngium (Apiaceae) occurred in the ancestor of all recent Balacha species. They seem to be restricted to living inside the leaf rosettes, and their synapomorphic depressed body and small size appear to be adaptations to this environment. Balacha and their Eryngium hosts occur in grassland areas in temperate South America, but at lower latitudes, they are isolated in alpine meadows on the peaks of the Southeastern Brazilian highlands. Dispersal between such areas in recent times through areas of lowland tropical humid Atlantic forest would be impossible, thus the ancestor of Balacha was probably distributed in southeastern South America before the uplift of these Brazilian mountain ranges, during the latest Eocene or Oligocene. This event may have triggered speciation of some lineages of this genus by vicariance.
Keywords: leafhopper, Cicadellini
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