| Tettigonioidea is a major superfamily in Ensifera, belonging to Orthoptera, Insecta. The insects in this superfamily distributed all over the world, while the most species were found in warmer areas, such as tropical and subtropical region. In China, there were about 300 species within Tettigonioidea in records. Less species of katydids lived in northeast China for the cold climate. And the species of katydids recorded in the literatures were approximately 40.According to the existing research, the katydids exhibited in northeast area belonged to four families, including Tettigoniidae, Conocephalidae, Phaneropteridae and Bradyporidea.Almost every kind of insect in Tettigonioidea could produce songs and the katydids were the most famous singer in Insecta. Though the study of the calling songs of katydids were abundant, most studies upon this question focused on only one or several species. The systematically exposition of calling songs of Tettigoioidea were rather rare. In this paper,combining the field investigation and indoor experimental analysis, multiple technological means have been applied in this study, including biology, ecology, molecular biology,acoustic, scanning electron microscope and so on. The author attempted to research the songs and stridulatory apparatus of Tettigonioidea distributed in Northeast China from three levels,interspecific level, subspecies level and intraspecific level.1. interspecific levelIn this part, the song characters including time-domain characters and frequency-domain characters of 22 species of Tettigonioidea were described and then the cluster analysis based on song features were carried out. The 22 species of Tettigonioidea belonged to 4 families, 12 genera were:(1)Bradyporidae, Deracantha onos Pallas, 1772;(2) Conocephalidae, Conocephalus chinensis Redtenbacher, 1891; Conocephalus fuscus Fabriicius, 1793; Conocephalus japonicus minutus Bey-Bienko, 1954; Ruspolia jezoensis Matsumura & Shiraki, 1908;(3)Phaneropteridae, Phaneroptera falcata Poda, 1761; Ducetia japonica Thunberg, 1815;(4)Tettigoniidae, Gampsocleis sedakovii sedakovii Fischer-Waldheim, 1846; Gampsocleis sedakovii obscura Walker, 1869; Gampsocleis gratiosa Brunner von Wattenwyl, 1862;Gampsocleis ussuriensis Adelung, 1910; Uvarovites inflatus Uvarov, 1924; Decticus verrucivorus Linnaeus, 1758; Decticus nigrescens Serg. Tarbinsky, 1930; Tettigonia ussuriana Uvarov, 1939; Metrioptera bonneti I. Bolivar, 1890; Metrioptera bicolor Philippi,1830; Metrioptera ussuriana Uvarov, 1926; Metrioptera engelhardti Uvarov, 1926;Metrioptera brachyptera Linnaeus, 1761; Platycleis montana Kollar, 1833; Uvarovina daurica Uvarov, 1928.Experimental results got from song feature analysis and cluster analysis showed that all the species used in this study had broadband songs. Only two species(Gampsocleis ussuriensis and Gampsocleis gratiosa) had both harmonics and broadband songs. Different species had different calling songs, and even the morphologically similar species could bedistinguished easily using their acoustic signals. Nevertheless, the calling songs were relatively stable within species. As a consequence, the acoustic signals of katydids were species specific.In addition, the stridulatory organs of 27 species were examined and compared under stereoscope and scanning electron microscope(SEM). 27 species were comprised of 22 species used in acostic analysis and 5 new species, including(1) Conocephalidae,Conocephalus maculates Le Gouillou, 1841;(2) Phaneropteridae, Phaneroptera nigroantennta Brunner von Wattenwyl, 1878;(3) Phaneropteridae, Elimaea fallax BeyBienko, 1951;(4) Tettigoniidae, Atlanticus jeholensis Mori, 1935;(5) Tettigoniidae,Paratlanticus ussuriensis Uvarov, 1926.Results of the measurement, comparison and analysis of stridulatory organ displayed, as follow:Stridulatory organs of all the selected species were located on the Cu2 vein of the segmental venter of light forewing. The teeth composed the stridulatory file was clavate,except the Conocephalidae with the granular teeth. The teeth were relative thick, and the interval between teeth was inconsistent. All the teeth arranged in an arc line and the both ends of file incurved. Although the stridulatory file feature of katydids were also the important basis in classification, they couldn’t be used as the classified index separately and need to cooperate with other indicators.2. Intraspecific levelThe research of acoustic signal and stridulatory organ divergence within species could divide into three aspects: individuals exhibit in different regions; individuals with different wing morphs; and individuals with different body colors.(1) Individuals exhibit in different regionsIn this part, the M. bicolor(the same wing morph and body color) from different geographic populations were seen as the study objects. The acoustic signal and stridulatory organs were analyzed, and then the cluster analysis was carried out. The results of the study were as following: the individuals in different geographical populations had different calling songs, while the morphological traits were identical among the populations. Through the cluster analysis, individuals collected from eight regions were divided into three classes, and these results were corresponded with the geographic distribution. Namely, the closer the individuals distributed, the similar the acoustic signal was. Based on this result, the “dialect”phenomenon existed in M. bicolor, and this divergence of calling song within species was not caused by morphological changes. Compared with previous research, the experimental range was so small. But the results showed that the calling song divergence also happened even with a small geographical distribution. Moreover, this result also supported the “acoustic adaption hypothesis”. In addition, our results were corresponded with the conclusion that the evolutionary rate of acoustic signal was quicker than that of morphology.(2) Individuals with different wing morphsIn this part, the author chose the Metrioptera bicolor as the research object. The longwinged morph and the short-winged morph were compared with each other for acousticsignals and stridulatory organs. The results showed that there were obvious differences in acoustic signals between these two morphs, while, for other index, there were identical in exception of the length of forewings. The long-winged morphs made more energetic songs. In the previous study, this kind of songs was preferred by females. Based on this study, the author thought that the macropters produced more attractive songs to compensate the disadvantage in fecundity. It was a tradeoff between flight and reproduction.(3) Individuals with different body colorsIn this part, Gampsocleis sedakovii obscura were seen as the study object. Compare the acoustic traits and stridulatory features of individuals with different body colors, and some relative molecular data were also analyzed. The results as follow: the individuals of G. s.obscura with different body color have the same stridulatory file, and there were no obvious difference between them. While, there were some differences between acoustic traits,especially in the time-domain characteristics. Though these two types located in the same region, they occupied the different biotope. The author thought that different biotope might be one of the major factors to the acoustic divergence. But it needs to further discuss for relative mechanism of acoustic divergence for the individuals in G. sedakovii with different body color.3. Subspecies levelIn this part, Gampsocleis sedakovii were seen as the research object. Through the analysis of the acoustic signals, morphological features and molecular data, of G. sedakovii collected from six region, then cluster analysis were carried out. The results following:There were obvious differences of acoustic signals and molecular data among the individuals of G. sedakovii collected from different locations. Except the number of teeth of stridulatory file, the other morphological features, including the length of forewings, the width of the teeth, the length of pronotum and body length, were also different among six geographical populations. From three aspect, acoustic signal, morphology and gene, the results of cluster analysis were consistent. G. sedakovii from six geographical populations were bisected into two branches. The individuals from JDM, BYCG and CES formed one branch; the other three populations composed one branch. This result supported the research conclusion that there were two subspecies within G. sedakovii. In addition, the author found the G. sedakovii from ELC were thought to be a “transitional type”, because the individuals inhabit in ELC had the middle data from all the 3 aspects. Through the above study, acoustic signal changed gradually during the subspeciation. The existing studies confirmed that the northeast region was the differentiation center of G. sedakovii. In the process of diffusion,evolution took the form of radiation. Combined with the previous studies, the author thought that ELC was closer to the center of differentiation of G. sedakovii within the locations we selected in this study. WCG was close to CES and far away from JDM and BYCG, while in the cluster analysis, individuals collected from WCG got together with those collected from JDM and BYCG. This result broke the conception that the classification of subspecies needs to be based on differences in geographical region. However, although distributed in geographically close regions, individuals might belong to different subspecies. And theclimate condition and environment might be the major factor to subspeciation. This conclusion was identical with the study in Apis cerana.Through the above research results, it could be seen that the acoustic songs of katydids were species specific and intraspecific stability. So the acoustic signals could be used for the classification and identification of species, especially for the individuals which difficult to distinguish from morphology or the cryptic species. Though the stridulatory organs were the important indicator, they could not used as the index for classification by itself. Subspecies and species with different biotype or exhibition had the different calling songs. Acoustic signals played a crucial role in mating behaviour, and it could be used as a barrier before reproduction. So the author though that the katydids with different calling songs would be evolved into different directions. After a long evolutionary process, the new species formed.Given all this, through analyzing the acoustic signals and stridulatory organs of Tettigonioidea in Northeast region systematically, the research carried out from interspecific,subspecies and intraspecific level. This study not only provided the abundant basic acoustic data of Tettigoniodiea, but also filled the blank in the acoustic study of systematic entomology of Tettigonioidea. Acoustic signals could provide fundamental basis for systematic entomology and speciation. |
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