Dialects of Metrioptera bicolor (Orthoptera: Tettigonioidea): Intraspecific Acoustic Signal Divergence in a Small-Scale Geographical Distribution

We present an analysis of the calling songs of species Metrioptera bicolor isolated from different locations within Northeast China illustrating the intraspecies calling song divergence. Recording and analysis of the male calling songs of some acoustic characters were performed and five morphological traits of M. bicolor were examined under stereoscope microscope and scanning electron microscope. A cluster analysis was made based on the song properties and the morphology of stridulatory organs. All the song traits, except the pulse number per pulse group, differ distinctly within species collected at different localities, while the pulse number of each pulse group and all the five morphological characters were consistent across locations. The cluster analysis showed that M. bicolor collected from eight sampling sites grouped into two branches and were consistent with geographical distribution.The dialect phenomenon exists in insects and the divergence of acoustic signals occurs in a small-scale geographical region and may be an early stage of speciation. We inferred that the divergence of intraspecific acoustic signals on a small-scale may result from different habitats. This study provides evidence for insect acoustic signal divergence, speciation, and insect acoustic signal evolution.