Spectral selectivity during phonotaxis: a comparative study in Neoconocephalus (Orthoptera: Tettigoniidae)

Abstract

SUMMARY The calls of male Neoconocephalus have most energy concentrated in a relatively narrow low-frequency band. In N. robustus this low-frequency band is centered around 7 kHz, whereas calls of N. nebrascensis and N. bivocatus have center frequencies close to 10 kHz. The importance of the position of the low-frequency band for female phonotaxis in these three species was determined using a walking compensator. Female N. robustus showed significant phonotaxis towards call frequencies from 5 to 10 kHz, and spectral selectivity towards higher frequencies did not change with stimulus amplitude. Significant responses in N. nebrascensis and N. bivocatus occurred at significantly higher frequency ranges than in N. robustus. In these species,spectral selectivity changed with stimulus amplitude; at 68 dB sound pressure level (SPL), upper cut-off frequency was significantly lower than at 80 dB SPL in both species. Adding a higher harmonic to the conspecific carrier frequency had a strong inhibitory effect on phonotaxis in N. robustus: at higher relative amplitudes of the harmonic, phonotaxis was completely suppressed. Adding a higher harmonic to the conspecific carrier frequency had a much weaker but significant inhibitory effect in N. nebrascensisand little, if any, effect in N. bivocatus. The processing of song spectrum in the sensory system is discussed with regard to the differences in spectral selectivity among the three species. The sharp spectral selectivity of N. robustus is interpreted as an adaptation for species isolation.

Molecular Phylogenetics of the Genus Neoconocephalus (Orthoptera, Tettigoniidae) and the Evolution of Temperate Life Histories

“…Typically, among co-occurring species calls differ distinctly in their temporal pattern, which allows females to selectively approach conspecific males [14], [22], [45]. Species with similar temporal patterns are typically not found signaling at the same time and place.…”

SINGING AND HEARING INAEROTEGMINA KILIMANDJARICA(TETTIGONIIDAE: HEXACENTRINAE), A SPECIES WITH UNUSUAL LOW CARRIER FREQUENCY OF THE CALLING SONG

“…T. cantans females are -unlike Aerotegmina -most sensitive to this preferred frequency. Even more similar to Aerotegmina could be the situation in Neoconocephalus robustus, where females prefer frequencies lower than the frequency they are most sensitive to (Schul & Patterson 2003;Deily & Schul 2006; see also Counter 1977). The reason for this behaviour, however, is assumed to be species isolation, definitively not important in Aerotegmina kilimandjarica with only one allopatric congeneric species.…”

Character State Reconstruction of Call Diversity in the Neoconocephalus Katydids Reveals High Levels of Convergence

“…Neoconocephalus calls are produced during opening and closing of the forewings (elytra); loud sound pulses are produced during the closing, while sounds during the opening are typically much softer22 and are not required for female responses (e.g 1718 , 24 , 25; but see 26). We therefore limit our description of the temporal pattern to the closing pulses and refer to them simply as 'pulses.'…”

“…15 , 16 , 17 , 18), call mechanics19 , 20 , 21 , 22, female preferences (e.g. 23 , 24 , 25 , 26), and sensory processing (e.g. 27 , 28 , 29 , 30 , 31).…”