@article {57636, title = {Listening for males and bats: spectral processing in the hearing organ of Neoconocephalus bivocatus (Orthoptera: Tettigoniidae)}, year = {2007}, abstract = {

Tettigoniids use hearing for mate finding and the avoidance of predators (mainly bats). Using intracellular recordings, we studied the response properties of auditory receptor cells of Neoconocephalus bivocatus to different sound frequencies, with a special focus on the frequency ranges representative of male calls and bat cries. We found several response properties that may represent adaptations for hearing in both contexts. Receptor cells with characteristic frequencies close to the dominant frequency of the communication signal were more broadly tuned, thus extending their range of high sensitivity. This increases the number of cells responding to the dominant frequency of the male call at low signal amplitudes, which should improve long distance call localization. Many cells tuned to audio frequencies had intermediate thresholds for ultrasound. As a consequence, a large number of receptors should be recruited at intermediate amplitudes of bat cries. This collective response of many receptors may function to emphasize predator information in the sensory system, and correlates with the amplitude range at which ultrasound elicits evasive behavior in tettigoniids. We compare our results with spectral processing in crickets, and discuss that both groups evolved different adaptations for the perceptual tasks of mate and predator detection.

}, keywords = {acoustic communication, hearing, Predator evasion, Receptor tuning, ultrasound}, doi = {10.1007/s00359-007-0245-7}, url = {http://link.springer.com/10.1007/s00359-007-0245-7}, author = {H{\"o}bel, Gerlinde and Schul, Johannes} } @article {47919, title = {Flight of the bumble bee: Buzzes predict pollination services}, journal = {PLOS ONE}, volume = {12}, year = {2017}, month = {Jul-06-2017}, pages = {e0179273}, abstract = {

Multiple interacting factors drive recent declines in wild and managed bees, threatening their pollination services. Widespread and intensive monitoring could lead to more effective management of wild and managed bees. However, tracking their dynamic populations is costly. We tested the effectiveness of an inexpensive, noninvasive and passive acoustic survey technique for monitoring bumble bee behavior and pollination services. First, we assessed the relationship between the first harmonic of the flight buzz (characteristic frequency) and pollinator functional traits that influence pollination success using flight cage experiments and a literature search. We analyzed passive acoustic survey data from three locations on Pennsylvania Mountain, Colorado to estimate bumble bee activity. We developed an algorithm based on Computational Auditory Scene Analysis that identified and quantified the number of buzzes recorded in each location. We then compared visual and acoustic estimates of bumble bee activity. Using pollinator exclusion experiments, we tested the power of buzz density to predict pollination services at the landscape scale for two bumble bee pollinated alpine forbs (Trifolium dasyphyllum and T. parryi). We found that the characteristic frequency was correlated with traits known to affect pollination efficacy, explaining 30\–52\% of variation in body size and tongue length. Buzz density was highly correlated with visual estimates of bumble bee density (r = 0.97), indicating that acoustic signals are predictive of bumble bee activity. Buzz density predicted seed set in two alpine forbs when bumble bees were permitted access to the flowers, but not when they were excluded from visiting. Our results indicate that acoustic signatures of flight can be deciphered to monitor bee activity and pollination services to bumble bee pollinated plants. We propose that applications of this technique could assist scientists and farmers in rapidly detecting and responding to bee population declines.

}, doi = {10.1371/journal.pone.0179273}, url = {http://dx.plos.org/10.1371/journal.pone.0179273}, author = {Miller-Struttmann, Nicole E. and Heise, David and Schul, Johannes and Geib, Jennifer C. and Galen, Candace}, editor = {Borges, Renee M.} } @article {20904, title = {Evolutionary diversification of the auditory organ sensilla in Neoconocephalus katydids (Orthoptera: Tettigoniidae) correlates with acoustic signal diversification over phylogenetic relatedness and life history}, journal = {Journal of Evolutionary Biology}, year = {2017}, month = {Jan-03-2017}, abstract = {

Neoconocephalus tettigoniids are a model for the evolution of acoustic signals as male calls have diversified in temporal structure during the radiation of the genus. Tettigoniidae have hearing organs in the forelegs with species-specific numbers of auditory sensilla in a linear crista acustica. We investigated changes of the hearing organs during an evolutionary radiation with divergence of intraspecific acoustic signals. We compared the neuroanatomy of the crista acustica from 9 Neoconocephalus species with different temporal call features, life histories, and from different phylogenetic positions. Average numbers of auditory sensilla were species-specific, ranging between 32\–35 sensilla. It is likely under sexual selection for detection of male calls and natural selection for detection of bat calls. We found statistically significant differences in sensillum numbers among species, but no relationship of crista acustica length or sensillum number with phylogenetic position or life history. Statistically significant correlations existed with call patterns: species with slow pulse rates had significantly higher numbers of auditory sensilla and a longer crista acustica. Further, species with a derived double-pulsed calls had longer cristae, and continuous callers had a higher number of auditory sensilla. Correlations with crista length were stronger than with the number of auditory sensilla. The hearing organs show considerable diversity between species despite their recent divergence and morphological and ecological similarities. Thus, they have the potential to respond to various selective pressures, including divergence of temporal and spectral signal properties. Phylogenetic constraints are unlikely to limit the evolutionary change of the auditory systems.

}, keywords = {hearing organ, insects, radiation, sensory evolution, sexual selection, signal evolution, tympanal organ}, doi = {10.1111/jeb.13066}, url = {http://doi.wiley.com/10.1111/jeb.13066}, author = {Strau{\ss}, Johannes and Alt, Joscha A. and Ekschmitt, Klemens and Schul, Johannes and Lakes-Harlan, Reinhard} }