The use of bioacoustic characters for distinguishing between cryptic species in insects: Potentials, restrictions, and prospects

Abstract

Differences in acoustic signal patterns between closely related species often form the main precopulatory reproductive barrier in insects. For this reason, discrimination between similar forms based on their signal patterns allows one to recognize reproductively isolated species. A calling signal produced by a mature male for attracting a conspecific female is a “species ID” testifying to the fact that it belongs to the same species. This is the reason why the use of the calling signal analysis for discriminating between cryptic species or elucidating the taxonomic rank of dubious forms is highly efficient. In certain species, courtship signals also show species-specific patterns. In insect taxonomy, the study of acoustic signals is most promising in morphologically or/and ecologically heterogeneous groups. Chances that any morphologically homogeneous form will actually appear to be a complex of cryptic species are low. The degree of signal variability differs in different orders, families and even congeneric species. Therefore, in every taxon investigated for the first time, it is necessary to evaluate the limits of intraspecific variability of signals before using the acoustic characters in taxonomy. Species not involved in acoustic interactions due to allopatry, different host specialization, etc. can produce calling signals with identical patterns. Consequently, similarity in the signal structure in such species is by no means evidence of their synonymy.