@article {53154, title = {Evolutionarily conserved coding properties favour the neuronal representation of heterospecific signals of a sympatric katydid species}, journal = {Journal of Comparative Physiology A}, volume = {204}, year = {2018}, month = {Jan-10-2018}, pages = {859 - 872}, abstract = {

To function as a mechanism in premating isolation, the divergent and species-specific calling songs of acoustic insects must be reliably processed by the afferent auditory pathway of receivers. Here, we analysed the responses of interneurons in a katydid species that uses long-lasting acoustic trills and compared these with previously reported data for homologous interneurons of a sympatric species that uses short chirps as acoustic signals. Some interneurons of the trilling species respond exclusively to the heterospecific chirp due to selective, low-frequency tuning and \“novelty detection\”. These properties have been considered as evolutionary adaptations in the sensory system of the chirper, which allow it to detect signals effectively during the simultaneous calling of the sympatric sibling species. We propose that these two mechanisms, shared by the interneurons of both species, did not evolve in the chirper to guarantee its ability to detect the chirp under masking conditions. Instead we suggest that chirpers evolved an additional, 2-kHz component in their song and exploited pre-existing neuronal properties for detecting their song under masking noise. The failure of some interneurons to respond to the conspecific song in trillers does not prevent intraspecific communication, as other interneurons respond to the trill.

}, keywords = {Auditory processing, insects, Selective coding, signal detection, signal evolution}, issn = {0340-7594}, doi = {10.1007/s00359-018-1282-0}, url = {http://link.springer.com/10.1007/s00359-018-1282-0}, author = {Kostarakos, Konstantinos} } @article {50908, title = {Subspecies-specific song preferences and diverged heterospecific discrimination in females of the bush-cricket Isophya kraussii (Orthoptera: Phaneropterinae)}, journal = {Biological Journal of the Linnean Society}, year = {2017}, month = {Sep-09-2017}, abstract = {

Divergence of the acoustic signals used in mate calling may be an important driver of speciation. Male song may vary accordingly to, in mismatch with or independently of female preferences. Therefore, to estimate the importance of male signal variation between subspecies, female preferences against subspecies-specific signal variants must be tested. We examined the female response probability in the two subspecies of the bush-cricket Isophya kraussii for consubspecific and heterosubspecific male signals, and also for the song of a closely related species (I. camptoxypha), which is sympatric with one, but allopatric to the other subspecies. Performing no-choice playback experiments, we found that females of both subspecies responded to the male song of their own subspecies with significantly higher probability than to heterosubspecific and heterospecific songs. Response specificity for consubspecific vs. heterosubspecific signals was not significantly asymmetric comparing the two subspecies. A significant difference was found, however, in the discrimination of heterospecific calls: females showed stronger discrimination against the song of I. camptoxypha in the subspecies sympatric with that species. Our results are best explained by a tightly covarying, stepwise coevolution of male signals and female preferences.

}, keywords = {acoustic communication, mate recognition, signal evolution, speciation}, issn = {0024-4066}, doi = {10.1093/biolinnean/blx094}, url = {http://academic.oup.com/biolinnean/article/doi/10.1093/biolinnean/blx094/4110201/Subspeciesspecific-song-preferences-and-diverged}, author = {Kirill M{\'a}rk Orci and Ionut Stefan Iorgu} } @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} }