A narrow hybrid zone between the grasshoppers Stenobothrus clavatus and S. rubicundus: courtship song analysis
V. Vedenina (1), J. Sradnick (2), A. Kloepfel (2), N. Elsner (2)

1) Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoy Karetny per. 19, 127994 Moscow, Russia. E-mail: vedenin@iitp.ru
2) Department of Neurobiology, Johann-Friedrich-Blumenbach-Institute, Berliner Str. 28, D-37073 Göttingen, Germany

The closely related grasshopper species Stenobothrus rubicundus and S. clavatus are known to hybridize in a very narrow contact zone on Mt. Tomaros in northern Greece. These species produce very different and complex courtship songs accompanied with visual display. We analyzed the courtship songs and underlying stridulatory movements of the hind legs in natural hybrids from the Mt. Tomaros. The two species were also hybridized in the laboratory and their songs were compared with the songs of the natural hybrids. Some hybrid songs were shown to have intermediate features between parental songs, whereas other hybrid songs comprised completely new elements. The clavatus-like song elements were found to dominate in hybrid songs. These song features may influence the mating success of hybrid males in the contact zone. A comparison of hybrid songs with the song pattern of the North-European S. rubicundus populations allowed us to suggest a scenario of S. rubicundus and S. clavatus origin.