Behaviour 2019
How Does the Central Nervous System (CNS) Change When New Call Types Evolve?
Johannes Schul, Kai Murphey, Darah Oxford, Javier Kelly Cuenca, Eduardo Favela. University of Missouri, Columbia, MO, United States

The calls of Neoconocephalus katydids (Insecta:Tettigoniidae) are the most diverse, and often species defining, trait in this genus. One line of diversification is adding a second rhythm (chirp rhythm) to the basic pulse rhythm of the calls. The neural structures (central pattern generators CPG) that generate call patterns and their locations in the CNS are unknown. We performed lesion experiments to localize the CPGs and determine how CPG structure changed during the evolution of a chirp rhythm.
Severing increasing numbers of abdominal ganglia leads to decreasing quality of the chirp pattern and lowers probability of calling. This indicates that the chirp CPG is distributed among ganglia A2 to A8. In species without chirp pattern abdominal lesions have no effect on the calls. 
Lesions of thoracic ganglia and connectives allow conclusions on the structure of the pulse pattern CPG. Effects of these lesions on calling parallel effects on flight. In addition, stimuli inducing flight (wind) also induce short call bouts. These two findings suggest that the pulse CPG has similar structure as the flight CPG and was likely derived from it during the evolution of calling in katydids.