Scale effects and constraints for sound production in katydids (Orthoptera: Tettigoniidae): correlated evolution between morphology and signal parameters

Male katydids (Orthoptera: Tettigoniidae) produce mating calls by rubbing the wings together, using specialized structures in their forewings (stridulatory file, scraper and mirror). A large proportion of species (ca. 66%) reported in the literature produces ultrasonic signals as principal output. Relationships among body size, generator structures and the acoustic parameters carrier frequency (f_c) and pulse duration (p_d), were studied in 58 tropical species that use pure‐tone signals. A comparative analysis, based on the only available katydid phylogeny, shows how changes in sound generator form are related to changes in f_c and p_d. Anatomical changes of the sound generator that might have been selected via f_c and p_d are mirror size, file length and number of file teeth. Selection for structures of the stridulatory apparatus that enhance wing mechanics via file‐teeth and scraper morphology was crucial in the evolution of ultrasonic signals in the family Tettigoniidae.     

Increase in song frequency decreases spermatophore size: correlative evidence of a macroevolutionary trade-off in katydids (Orthoptera: Tettigoniidae)

In many katydids, the male feeds his mate with a large gelatinous spermatophore. Males of most species also produce elaborate calling songs. We predicted a negative relationship between spermatophore size and call frequency because of trade-offs between these two costly traits. Our comparative analysis controlling phylogeny and body size supported this prediction. Although call frequency is expected to decrease with increasing body size, after controlling for phylogeny, both variables were not related. Finally, given that song frequency and spermatophore size are likely targets of sexual selection, we examined the relationship between these variables and sexual size dimorphism (SSD) which can be influenced by sexual selection on body size. We found that only female body size was positively related to SSD, suggesting that natural and/or sexual selection on female body size may be stronger than sexual selection on male and spermatophore size.     

Sound production in two species of damselfishes (Pomacentridae): Plectroglyphidodon lacrymatus and Dascyllus aruanus

Agonistic sounds of two pomacentrid species, Plectroglyphidodon lacrymatus and Dascyllus aruanus , were recorded in captivity. Plectroglyphidodon lacrymatus produced trains of 2–5 pops, each composed of 18–25 cycles, with an average duration of 56 ms; most energy ranged from c. 100 to 1000 Hz. Dascyllus aruanus produced pops and chirps. Pops were generally composed of a single pulse, with 2–14 peaks and an average duration of 6·7 ms. Pops contained energy >4 kHz, and peak frequency ranged from 680 to 1300 Hz. Chirps consisted of trains of 12–42 short pulses of three to six cycles, with durations varying from 0·6 to 1·27 ms; peak frequency varied from 3400 to 4100 Hz. Sound production in P. lacrymatus suggested that pomacentrids are derived from an ancestral taxon capable of sound production and that this capacity is a synapomorphy for the family. Although in the Pomacentridae, pops are typically composed of a single pulse, which is longer and higher pitched than chirps composed of a series of shorter pulses, D. aruanus chirps were higher pitched than its pops. Thus, acoustic variation in the genus Dascyllus is probably not more restricted than in the Pomacentridae.     

两种纺织娘线粒体基因组的比较分析

目前关于螽斯科昆虫的线粒体基因组全序列及其分子进化的研究报道很少。本研究利用L-PCR技术结合嵌套步移PCR扩增获得纺织娘Mecopoda elongata和日本纺织娘M. niponensis的线粒体基因组全序列, 同时对二者之间的碱基组成和结构特点进行了比较分析。结果显示： 纺织娘线粒体基因组（GenBank登录号JQ917910）序列全长15 284 bp, A+T含量71.8%; 日本纺织娘线粒体基因组（GenBank登录号 JQ917909）序列全长15 364 bp, A+T含量72.4%; 2种纺织娘序列长度差异主要是控制区长度不同引起（纺织娘控制区长294 bp, 日本纺织娘控制区长393 bp）。2种纺织娘基因组基因含量、 相对位置及转录方向均与其他已报道的螽斯科昆虫一致, 未发现基因重排现象; 基因组中均存在较长的间隔序列, 在trnA/trnR之间的间隔序列长度分别为63 bp与68 bp, 在trnQ/trnM之间的分别为55 bp和26 bp, 在trnS^UCN/nad1之间的均为21 bp。而最长的基因重叠区域在2种纺织娘trnC/trnW之间均为8 bp, 在atp8/atp6和nad4L/nad4L之间均为7 bp。蛋白质编码基因的碱基组成和密码子使用均具有明显的偏倚性; 除nad1和nad2以特殊的TTG作为起始密码子, cox1使用特殊的起始密码子ATGA外, 其余的10种蛋白质编码基因均使用典型的ATN作为起始密码子。在tRNA基因中, 除trnS^AGN外, 均能折叠形成典型的三叶草形二级结构。在这些tRNA基因中均存在一定数目的以G-U错配为主的碱基错配, 类似现象同样存在于其他已测定的六足动物线粒体基因组中, 表明G-U配对在线粒体基因组中很可能是一种完全正常的碱基配对方式。基因组中控制区的A+T含量略低于线粒体基因组的其他区域, 表明高A+T含量并不是该区域的必要特征。本研究结果为螽斯科系统发生关系重建积累了有价值的数据资料。     

Disentangling determinants of egg size in the Geometridae (Lepidoptera) using an advanced phylogenetic comparative method

We present a phylogenetic comparative study assessing the evolutionary determinants of egg size in the moth family Geometridae. These moths were found to show a strong negative allometric relationship between egg size and maternal body size. Using recently developed comparative methods based on an Ornstein-Uhlenbeck process, we show that maternal body size explains over half the variation in egg size. However, other determinants are less clear: ecological factors, previously hypothesized to affect egg size, were not found to have a considerable influence in the Geometridae. The limited role of such third factors suggests a direct causal link between egg size and body size rather than an indirect correlation mediated by some ecological factors. Notably, no large geometrid species lay small eggs. This pattern suggests that maternal body size poses a physical constraint on egg size, but within these limits, there appears to be a rather invariable selection for larger eggs.     

Contribution to the taxonomy of Gryllus Linnaeus, 1758 in South America: Part I: Redescription of Gryllus argentinus Saussure, 1874 (Orthoptera,Grylloidea, Gryllidae)

The genus Gryllus includes 82 described species that occur in America from Canada to Argentina as well as in several areas of Africa, Europe and Asia. There are 12 species in South America, which were described in the nineteenth century based on a small number of samples and inconsistent characters such as body coloration and external morphology. The aim of this article is to redescribe Gryllus argentinus Saussure, 1874 collected in the urban areas of Pelotas, Capão do Leão and Rio Grande, in the state of Rio Grande do Sul, southern Brazil, highlighting phallic sclerites, calling song and body morphometry. We designate the lectotype male, provide a combination of diagnostic characteristics and discuss the taxonomic situation of South American Gryllus species.     

Nobloedischia rasnitsyni, a new genus and species of Oedischiidae (Orthoptera) from the Lower Permian Wellington Formation of Oklahoma, USA

Nobloedischia rasnitsynigen. et sp. n. (Oedischiidae) is described from the Lower Permian Wellington Formation of Noble County, Oklahoma. The genus is similar to both Petrelcana (Oedischiidae: Mezenoedischiinae) and Oedischia (Oedischiidae: Oedischiinae) and is left unplaced at the subfamily level. The new species is the twelfth Orthoptera species and the fourth species of Oedischiidae from these deposits.     

A taxonomic revision and species delimitation of the genus Purpuraria Enderlein, 1929 (Orthoptera: Pamphagidae) using an integrative approach

Recent studies on the endemic Canarian genus Purpuraria have shown that the taxonomy of its only recognized species (P. erna) is probably erroneous. In this study, an integrative revision of the genus is performed, based on a large number of specimens and geographical sampling. As a result, (1) the diagnostic characters at the genus level are re‐described, (2) Purpuraria magna n. sp. based on morphological, morphometric and genetic data is described and (3) the taxonomic status of a formerly described subspecies is clarified. Intraspecific and interspecific morphometric differences have been found, indicating that the genus is undergoing a process of morphological diversification. Nevertheless, the possibility of interspecific mating between individuals of the two species is suggested, because no significant differences have been found between their respective calling songs. Genetic analyses using mitochondrial and nuclear DNA sequences suggest that P. erna and P. magna are recent species with evidences of secondary contact episodes in the past.     

Differences in distress: Variance and production of American Crocodile (Crocodylus acutus) distress calls in Belize

Acoustic communication of American Crocodiles (Crocodylus acutus) is relatively understudied. Our overall aim was to determine the acoustic structure of wild American Crocodile distress calls, distinguish call differences among size classes (hatchling, juvenile, sub‐adult, and adult), and investigate call production on a gradient of human disturbance. American Crocodile distress calls have strong frequency modulation and are comprised of multiple harmonics in a downsweeping pattern. Measured parameters (total duration, first quartile duration, maximal frequency, first quartile frequency, end frequency, slope of first quartile, slope of last quartiles) differed significantly among size classes (p < .05). Hatchling distress calls are higher in frequency and strongly modulated, whereas calls produced by sub‐adults and adults showed little modulation, are lower in frequency, and have greater overall duration. Proportion of crocodiles that produced distress calls during capture differed by size class and sampling location, particularly adult distress calls which are reported here to be produced with undocumented frequency. We determined that American Crocodiles of all size classes produce distress calls at varying rates among study sites. Our results demonstrate that American crocodiles produce distress call more frequently at sites with higher anthropogenic activity. Measured call parameters of juveniles and hatchling American crocodiles also varied among sites in relation to human disturbance. Calls recorded at sites of high anthropogenic impact have increased duration and less modulation which may adversely affect response to emitted distress calls. Proportional and call parameter variances suggest anthropogenic activity as a driver for increased call production and alteration of call parameters at high human‐impacted sites.     

Individual variation in body color in the field cricket Teleogryllus occipitalis (Orthoptera: Gryllidae)

Body color of animals may affect individual fitness through direct effects on various processes, such as predatory avoidance, thermoregulation, UV resistance, and mating behavior. Body color variation of the field cricket Teleogryllus occipitalis (Audinet‐Serville) (Orthoptera: Gryllidae) is often observed. We quantified the individual variation in body color of this species by measuring the luminance of hind leg femur. Thereafter, we examined whether the body color was a heritable trait or not using parent–offspring analysis. In addition, the effect of body color of both parents on body size, sex ratio, and survival rate of progeny was investigated. The results showed that maternal body color was not heritable, whereas paternal body color was correlated with the body color of the progeny. Body size and sex ratio were not correlated with body color of parents. Although paternal body color did not affect the survival rate of the progeny beyond the stage of final instar nymph, progeny survival rate significantly increased with darkness of maternal body.     

Discriminating species of Sinipta Stål (Orthoptera: Acrididae) from Uruguay based on morphological,ethological and molecular data

Two species of the genus Sinipta, S. dalmani and S. hectorisperonii, exist in Uruguay, the latter reported here for the first time. Both species have quite similar morphological features and can only be distinguished by slight details, which have led to misidentifications in the past. Specimens from both taxa were studied in order to detect suitable characters to distinguish them and to clarify their taxonomic status, by integrating previously unstudied morphological, biological and molecular characteristics. Detailed structures of the stridulatory file of both sexes were studied and described for the first time, and the sounds produced by both species were studied and described on the basis of recordings made in captivity with an analog recorder. The signal was digitized and analyzed using Avisoft software. Three different types of sound were described for both species: calling song, courtship song and disturbance song. Oscillograms and frequency spectra were provided, and the physical characteristics of the sounds of interest for species identification were established. Finally, molecular studies showed that the two taxa are reciprocally monophyletic groups. The combined results of the analyses suggest that the two studied taxa are distinct species, and point to features suitable for their identification.     

Morphological and physiological differences of the auditory system in three related bushcrickets (Orthoptera: Phaneropteridae, Poecilimon)

Abstract. The auditory system of three closely related bushcrickets was investigated with respect to morphological and physiological differences. The size of the acoustic vesicle in the prothorax cavity and the size of the acoustic spiracle were compared to differences in auditory tuning of the tympanic nerve and differences in the directionality. The results indicate that a small auditory vesicle and auditory spiracle provide reduced sensitivity in the high frequency range (above 10—15 kHz), but increase sensitivity at low frequencies (below 10 kHz). The directionality of the hearing system deteriorates at frequencies between 10 and 25 kHz in species with a small spiracle and trachea. The evolutionary implications of these differences of the auditory systems are discussed. They are considered to be influenced more by ecological factors than bioacoustical ones.     

Female preference for large males in the bushcricketRequena sp. 5 (Orthoptera: Tettigoniidae)

Receptive females of the bushcricketRequena sp. 5 (Orthoptera: Tettigoniidae) are attracted to male calls. In this experiment we investigate whether females discriminate between males on the basis of their calls. When virgin females were presented with two males of different size, they preferred the larger male. Larger males produce calls with a lower carrier frequency compared to smaller males, suggesting that females may use male carrier frequency as a predictor of male size. Furthermore, larger males produce heavier spermatophores. This suggests that females may prefer to mate with larger males to receive large nuptial gifts.     

Extremely divergent song types in the genus Aerotegmina Hemp (Orthoptera: Tettigoniidae: Hexacentrinae) and the description of a new species from the Eastern Arc Mountains of Tanzania (East Africa)

The genus Aerotegmina comprises a group of African canopy-dwelling, predatory bushcrickets (katydids) that is known for its inflated tegmina and the unusually loud and low-frequency calling song of its type species. Here, we describe the songs of another two species of the genus which are much larger than the type species and have an even lower peak frequency. In addition, small and large species differ in song structure. While the type species and closely related forms have a broad banded, multi-peak song with strong components in the audio and ultrasonic range, the species treated here have an extremely narrow banded, resonant song with a carrier frequency of 2 kHz. With Q-values above 100 these sounds belong to the purest songs ever recorded in Orthoptera. Besides describing songs, stridulatory organs and a new species we discuss the possible functions of the song type. A key to the species of Aerotegmina is provided.     

Evolutionary diversification of the auditory organ sensilla in Neoconocephalus katydids (Orthoptera: Tettigoniidae) correlates with acoustic signal diversification over phylogenetic relatedness and life history

Neoconocephalus Tettigoniidae are a model for the evolution of acoustic signals as male calls have diversified in temporal structure during the radiation of the genus. The call divergence and phylogeny in Neoconocephalus are established, but in tettigoniids in general, accompanying evolutionary changes in hearing organs are not studied. We investigated anatomical changes of the tympanal hearing organs during the evolutionary radiation and divergence of intraspecific acoustic signals. We compared the neuroanatomy of auditory sensilla (crista acustica) from nine Neoconocephalus species for the number of auditory sensilla and the crista acustica length. These parameters were correlated with differences in temporal call features, body size, life histories and different phylogenetic positions. By this, adaptive responses to shifting frequencies of male calls and changes in their temporal patterns can be evaluated against phylogenetic constraints and allometry. All species showed well‐developed auditory sensilla, on average 32–35 between species. Crista acustica length and sensillum numbers correlated with body size, but not with phylogenetic position or life history. Statistically significant correlations existed also with specific call patterns: a higher number of auditory sensilla occurred in species with continuous calls or slow pulse rates, and a longer crista acustica occurred in species with double pulses or slow pulse rates. The auditory sensilla show significant differences between species despite their recent radiation, and morphological and ecological similarities. This indicates the responses to natural and sexual selection, including divergence of temporal and spectral signal properties. Phylogenetic constraints are unlikely to limit these changes of the auditory systems.     

Trade‐offs in the evolution of bumblebee colony and body size: a comparative analysis

Trade‐offs between life‐history traits – such as fecundity and survival – have been demonstrated in several studies. In eusocial insects, the number of organisms and their body sizes can affect the fitness of the colony. Large‐than‐average body sizes as well as more individuals can improve a colony's thermoregulation, foraging efficiency, and fecundity. However, in bumblebees, large colonies and large body sizes depend largely on high temperatures and a large amount of food resources. Bumblebee taxa can be found in temperate and tropical regions of the world and differ markedly in their colony sizes and body sizes. Variation in colony size and body size may be explained by the costs and benefits associated with the evolutionary history of each species in a particular environment. In this study, we explored the effect of temperature and precipitation (the latter was used as an indirect indicator of food availability) on the colony and body size of twenty‐one bumblebee taxa. A comparative analysis controlling for phylogenetic effects as well as for the body size of queens, workers, and males in bumblebee taxa from temperate and tropical regions indicated that both temperature and precipitation affect colony and body size. We found a negative association between colony size and the rainiest trimester, and a positive association between the colony size and the warmest month of the year. In addition, male bumblebees tend to evolve larger body sizes in places where the rain occurs mostly in the summer and the overall temperature is warmer. Moreover, we found a negative relationship between colony size and body sizes of queens, workers, and males, suggesting potential trade‐offs in the evolution of bumblebee colony and body size.     

Speciation in the greater galagos (Prosimii: Galaginae): review and synthesis*

A marked morphological and genetical discontinuity among the greater galagos points to the existence of two genetical species within the taxon, Galago crassicaudatus E. Geofl'roy 1812. This contribution investigates the conditions surrounding this speciation event, and places it within a phylogenetic context. Information pertaining to body size, litter size, sexual dimorphism, locomotor mode and karyotypic structure is assessed. It is hypothesized that G. crassicaudatus diverged from its more gracile sibling, G. garnettii, approximately 2 million years ago, in respotise lo the increasing aridification of Africa that accompanied the Northern Hemisphere Pleistocene glaciations.     

Morphological study of the Stridulatory Organ in two species of Crematogaster genus: Crematogaster scutellaris (Olivier 1792) and Crematogaster auberti (Emery 1869) (Hymenoptera: Formicidae)

The stridulatory organ of the Crematogaster scutellaris (Olivier 1792) workers is being described, comparing their pars stridens present in six nests of this species, with one nest of Crematogaster auberti Emery 1869 and with the bibliographical data regarding other neighbouring species at our disposal. Both species and some Crematogaster scutellaris nests have shown significant differences. We propose several hypotheses which could explain these differences.     

Transmission and perception of acoustic signals in the desert clicker,Ligurotettix coquilletti (Orthoptera: Acrididae)

Males of the desert clicker, Ligurotettix coquilletti (Acrididae: Orthoptera) defend a femalerequired resource, the creosote bush Larrea tridentata, in desert habitats of the southwestern United States. Males signal acoustically to each other as well as to searching females. The call is produced by tegminal/femoral stridulation where one or both legs are used for sound production. Sound pressure levels, measured laterally, are influenced by the intervening tegmen between the stridulating leg and the microphone. Differences in measured sound pressure levels between sides can vary up to 7 dB. When clicks are produced multiply,these multiple clicks may be 4 dB louder than single clicks. We examine the structure of the call and the effective broadcast area of single males by monitoring acoustic ascending neurons of the ventral nerve cord in the neck. By taking the neurophysiological preparation into the field, we were able to map the broadcast area of isolated males and also of males calling within aggregations. The distance over which the signal of isolated males could be detected was 8–14 m, whereas neural representation of the calls of males within aggregation were detectable within 4–6 m. The sound spectrum of the song, although having a major lower-frequency component around 10 kHz, has extensive power in the ultrasonic range. The tuning characteristics of the ascending auditory neuron matched the overall structure of the male call. The importance of the acoustic cue, as compared to visual cues, is discussed in relation to female attraction.