Overview on the diversity of sounds produced by clownfishes (Pomacentridae): importance of acoustic signals in their peculiar way of life

Acoustic fish community in the Madeira Archipelago (North Atlantic Ocean): Characterization of sound diversity and daily patterns

Marine ecosystems are increasingly subjected to anthropogenic pressures, which demands urgent monitoring plans. Understanding soundscapes can offer unique insights into the ocean status providing important information and revealing different sounds and their sources. Fishes can be prominent soundscape contributors, making passive acoustic monitoring (PAM) a potential tool to detect the presence of vocal fish species and to monitor changes in biodiversity. The major goal of this research was to provide a first reference of the marine soundscapes of the Madeira Archipelago focusing on fish sounds, as a basis for a long-term PAM program. Based on the literature, 102 potentially vocal and 35 vocal fish species were identified. Additionally 43 putative fish sound types were detected in audio recordings from two marine protected areas (MPAs) in the Archipelago: the Garajau MPA and the Desertas MPA. The Garajau MPA exhibited higher fish vocal activity, a greater variety of putative fish sound types and higher fish sound diversity. Lower abundance of sounds was found at night at both MPAs. Acoustic activity revealed a clear distinction between diurnal and nocturnal fish groups and demonstrated daily patterns of fish sound activity, suggesting temporal and spectral partitioning of the acoustic space. Pomacentridae species were proposed as candidates for some of the dominant sound types detected during the day, while scorpionfishes (Scorpaena spp.) were proposed as sources for some of the dominant nocturnal fish sounds. This study provides an important baseline about this community acoustic behaviour and is a valuable steppingstone for future non-invasive and cost-effective monitoring programs in Madeira.

The importance of context in the acoustic behaviors of marine, subtropical fish speciesa)

Despite the importance of acoustic signaling in fishes, the prevalence of the behavioral contexts associated with their active (i.e., intentional) sound production remains unclear. A systematized review was conducted to explore documented acoustic behaviors in marine, subtropical fishes and potential influences affecting their relative pervasiveness. Data were collected on 186 actively soniferous fish species studied across 194 publications, identified based on existing FishSounds and FishBase datasets. Disturbance was the most common behavioral context associated with active sound production-reported for 140 species or 75% of the species studied-and then aggression (n = 46 species, 25%) and reproduction (n = 34 species, 18%). This trend, however, somewhat differed when examined by research effort, study environment, and fish family, such as reproductive sounds being more commonly reported by studies conducted in the wild. The synthesis of fish sound production behaviors was in some ways stymied by the fact that many species' sound production did not have discernible associated behavioral contexts and that some investigations did not clearly identify the study environments in which active sound production was observed. These findings emphasize the importance of context-behavioral or otherwise-when studying acoustic behaviors in fishes.

Reliable characterization of sound features in fishes begins in open-water environmentsa)

Many fishes use sounds to communicate in a wide range of behavioral contexts. In monitoring studies, these sounds can be used to detect and identify species. However, being able to confidently link a sound to the correct emitting species requires precise acoustical characterization of the signals in controlled conditions. For practical reasons, this characterization is often performed in small sized aquaria, which, however, may cause sound distortion, and prevents an accurate description of sound characteristics that will ultimately impede sound-based species identification in open-water environments. This study compared the sounds features of five specimens of the silverspot squirrelfish Sargocentron caudimaculatum recorded at sea and in aquaria of different sizes and materials. Our results point out that it is preferable to record fish sounds in an open-water environment rather than in small aquaria because acoustical features are affected (sound duration and dominant frequency) when sounds are recorded in closed environments as a result of reverberation and resonance. If not possible, it is recommended that (1) sound recordings be made in plastic or plexiglass aquaria with respect to glass aquaria and (2) aquaria with the largest dimensions and volumes be chosen.

Shelter cleaning of frillfin goby as non-reproductive behaviour

Various animals perform nest cleaning behaviour for breeding and keeping the hygiene of their living environment. Some fishes are also known to clean the nest for breeding and parental care, but it is unclear whether they clean it under non-breeding conditions. This study investigated the shelter cleaning behaviour of frillfin goby (Bathygobius fuscus) during the non-breeding season. All individuals of both males and females removed unknown objects (fishing sinkers) from their shelter, whereas they did not move many sinkers in the feeding area located outside the shelter. Subsequent video observation showed that fish removed sinkers using their tail fin, snout, mouth, and pectoral fins. The results suggest that frillfin goby clean their shelter even under non-breeding conditions. Furthermore, this study found that they can use pectoral fins to move objects, just like other animals use their hands and forelimbs to do so, supporting the developmental relationship between digits and pectoral fins in terms of functionality.

First use of acoustic calls to distinguish cryptic members of a fish species complex

Although molecular methods and bioacoustical analysis have been used to uncover cryptic species, the combination of both methodologies is still rare. The humbug damselfish complex, Dascyllus aruanus, is composed of at least two species with Dascyllus aruanus in the Pacific Ocean and Dascyllus abudafur in the Indian Ocean. However, genetic data suggest that additional species could be found. Therefore, we aimed to determine whether the sounds produced by different populations of fish could help to distinguish cryptic species. Recordings of chase and courtship sounds were made on humbug damselfish populations from Madagascar, Taiwan and French Polynesia. Chase sound features are more variable than courtship sounds, suggesting more constraints on courtship sounds, since they would contribute to premating isolation. Comparison between courtship sounds show the variation in acoustic features between Taiwan and Madagascar align with genetic differences, supporting that sounds could discriminate cryptic species in Teleosts. Moreover, differences in both acoustic features and genetic data are also found between Taiwan and French Polynesia, suggesting two clearly distinct populations. Consequently, the name D. emamo can be resurrected for the Polynesian humbug damselfish. External phenotype traits do not allow the distinction between populations, illustrating that only behaviour has been modified.

Environmental Cues and Mechanisms Underpinning Sex Change in Fish

Fishes are the only vertebrates that undergo sex change during their lifetime, but even within this group, a unique reproductive strategy is displayed by only 1.5% of the teleosts. This lability in alternating sexual fate is the result of the simultaneous suppression and activation of opposing male and female networks. Here, we provide a brief review summarizing recent advances in our understanding of the environmental cues that trigger sex change and their perception, integration, and translation into molecular cascades that convert the sex of an individual. We particularly focus on molecular events underpinning the complex behavioral and morphological transformation involved in sex change, dissecting the main molecular players and regulatory networks that shape the transformation of one sex into the opposite. We show that histological changes and molecular pathways governing gonadal reorganization are better described than the neuroendocrine basis of sex change and that, despite important advances, information is lacking for the majority of hermaphrodite species. We highlight significant gaps in our knowledge of how sex change takes place and suggest future research directions.

Dominance Hierarchies in Marine Invertebrates

AbstractDominance hierarchies have been well studied in myriad terrestrial animals, but surprisingly little is known about hierarchies in marine invertebrates; examples are limited to a few species of decapod crustaceans and cephalopods. Is the marine environment less conducive to the establishment of dominance hierarchy structures, or does this just underline the lack of detailed behavioral information about most marine invertebrates? In this review, we highlight the published information about marine invertebrate dominance hierarchies, which involve ranks established through fights or displays. We focus on the method of hierarchy formation, examine the ecological implications of this population structure, and compare the habitat and behavioral characteristics of species that exhibit this behavior. Because dominance hierarchies can influence habitat use, population distributions, energetics, mating, resource exploitation, and population genetic structure, it is crucial to understand how this trait evolves and which species are likely to exhibit it. A better understanding of marine invertebrate hierarchies could change the way we think about population dynamics of some species and could have important implications for fisheries, conservation, or even modeling of social and economic inequality.

Sensory cues underlying competitive growth in the clown anemonefish (Amphiprion percula)

In some animal societies, access to breeding depends on the individual's position in a hierarchy, which often depends on an individual's size. In such societies, individuals may try to outgrow one another to attain a higher rank by engaging in a form of strategic growth (competitive growth). This suggests that members of the hierarchy can track changes in the growth and size of potential competitors and respond accordingly. The clown anemonefish, Amphiprion percula, is one species known to exhibit competitive growth at the initiation of size hierarchies. Here, we use 5 combinations of sensory cues to determine which cues must be available for individuals to engage in competitive growth. Our results show that mechanosensory (pressure and/or touch) cues or unobstructed interactions are necessary for competitive growth to occur. This study provides an understanding of the relationship between sensory cues and phenotypic responses to different social contexts.

Ecology of fish hearing

Underwater sound is directional and can convey important information about the surrounding environment or the animal emitting the sound. Therefore, sound is a major sensory channel for fishes and plays a key role in many life-history strategies. The effect of anthropogenic noise on aquatic life, which may be causing homogenisation or fragmentation of biologically important signals underwater is of growing concern. In this review we discuss the role sound plays in the ecology of fishes, basic anatomical and physiological adaptations for sound reception and production, the effects of anthropogenic noise and how fishes may be coping to changes in their environment, to put the ecology of fish hearing into the context of the modern underwater soundscape.

Semantic Associations Dominate Over Perceptual Associations in Vowel-Size Iconicity

We tested the influence of perceptual features on semantic associations between the acoustic characteristics of vowels and the notion of size. To this end, we designed an experiment in which we manipulated size on two dissociable levels: the physical size of the pictures presented during the experiment (perceptual level) and the implied size of the objects depicted in the pictures (semantic level). Participants performed an Implicit Association Test in which the pictures of small objects were larger than those of large objects - that is, the actual size ratio on the semantic level was inverted on the perceptual level. Our results suggest that participants matched visual and acoustic stimuli in accordance with the content of the pictures (i.e., the inferred size of the depicted object), whereas directly perceivable features (i.e., the physical size of the picture) had only a marginal influence on participants' performance. Moreover, as the experiment has been conducted at two different sites (Japan and Germany), the results also suggest that the participants' cultural background or mother tongue had only a negligible influence on the effect. Our results, therefore, support the assumption that associations across sensory modalities can be motivated by the semantic interpretation of presemantic stimuli.

Host choice and fitness of anemonefish Amphiprion ocellaris (Perciformes: Pomacentridae) living with host anemones (Anthozoa: Actiniaria) in captive conditions

In this study, we investigated the host choice of naïve Amphiprion ocellaris, a specialist, at two different stages of development (newly settling juveniles and post-settlement juveniles). The fish were exposed to their natural and unnatural host species in the laboratory and their fitness was assessed in terms of activity and growth rate. Newly settling juveniles exhibited little host preference, while post-settlement juveniles immediately associated with their most common host in the wild. The analysis of fish activity confirmed that A. ocellaris is diurnal; they are most active in the morning, less at midday and barely move at night. The average travelling distance of juveniles was shorter in the groups living with their natural host, increasing in the groups living with an unnatural host and was highest in groups that did not become associated with any other unnatural host species. Post-settlement juveniles living with the natural host species grew better than those living with unnatural hosts or without anemone contact. These results suggest that the welfare of A. ocellaris in captivity will be optimized by keeping them with their natural anemone host species, although more generalist Amphiprion species may survive in association with other hosts.

Effect of the UV-filter benzophenone-3 on intra-colonial social behaviors of the false clown anemonefish (Amphiprion ocellaris)

The UV-filter benzophenone-3 (BP-3) is widely used and is environmentally stable, lipophilic, and bioaccumulative. Previous in vitro and in vivo studies have shown that BP-3 can cause endocrine disrupting effects. However, little information is available on its ecotoxicity on coral reef fish. Agonistic behavior, which is regulated by the endocrine system, is crucial to the social structure of some coral reef fish species. Endocrine disruptors may disturb fish agonistic behavior and social interactions. In this study, we tested whether chronic BP-3 exposure can affect social behaviors in coral reef fish. Juvenile false clown anemonefish (Amphiprion ocellaris) were exposed to BP-3 via diet (0 and 1000 ng/g food) for 90 d. Through the experiment, each tank was videotaped and behavioral indicators of social status, including threatening, attacking, and submissive behaviors were quantitatively analyzed from the videos. Survival and growth were not affected by the BP-3 exposure except that the body weight of the dominant fish was higher in the BP-3 group. Social rankings were not changed by BP-3. Intra-colonial social behaviors were significantly affected only by rank but not by the BP-3 exposure. Our results suggest that BP-3 at environmental levels may not cause significant harm to social behavior of coral reef fish. However, more research is needed to better understand the behavioral effects of BP-3 in fish.

Ontogenetic and phylogenetic simplification during white stripe evolution in clownfishes

Background

Biologists have long been fascinated by the striking diversity of complex color patterns in tropical reef fishes. However, the origins and evolution of this diversity are still poorly understood. Disentangling the evolution of simple color patterns offers the opportunity to dissect both ultimate and proximate causes underlying color diversity.

Results

Here, we study clownfishes, a tribe of 30 species within the Pomacentridae that displays a relatively simple color pattern made of zero to three vertical white stripes on a dark body background. Mapping the number of white stripes on the evolutionary tree of clownfishes reveals that their color pattern diversification results from successive caudal to rostral losses of stripes. Moreover, we demonstrate that stripes always appear with a rostral to caudal stereotyped sequence during larval to juvenile transition. Drug treatments (TAE 684) during this period leads to a dose-dependent loss of stripes, demonstrating that white stripes are made of iridophores and that these cells initiate the stripe formation. Surprisingly, juveniles of several species (e.g., Amphiprion frenatus) have supplementary stripes when compared to their respective adults. These stripes disappear caudo-rostrally during the juvenile phase leading to the definitive color pattern. Remarkably, the reduction of stripe number over ontogeny matches the sequences of stripe losses during evolution, showing that color pattern diversification among clownfish lineages results from changes in developmental processes. Finally, we reveal that the diversity of striped patterns plays a key role for species recognition.

Conclusions

Overall, our findings illustrate how developmental, ecological, and social processes have shaped the diversification of color patterns during the radiation of an emblematic coral reef fish lineage.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0559-7) contains supplementary material, which is available to authorized users.

Scary clowns: adaptive function of anemonefish coloration

Clownfishes, with their showy coloration, are well known for their symbiosis with sea anemones and for their hierarchical reproductive system, but the function of their coloration is unclear. We used a phylogeny of 27 clownfish species to test whether fish coloration (i) serves a protective function that involves their anemone hosts, or (ii) signals species identity in species with overlapping host ranges that can potentially share the same host. We tested for an association between fish colour pattern traits, host morphology and host toxicity and examined coloration in relation to host sharing and geographic proximity. Fish with fewer stripes occupied fewer anemone species, and hosts with shorter tentacles, than fish with multiple stripes. There was a negative relationship between anemone toxicity and tentacle length and these protective traits together were correlated with the evolution of stripes. Host sharing or range overlap was not associated with coloration divergence. We propose that ancestral anemonefishes had multiple stripes that served for hiding/camouflage among the hosts' long tentacles, whereas increased specialization towards fewer and more toxic hosts (with shorter tentacles) led to the use of coloration as an aposematic signal. The intriguing notion that an aposematic signal could advertise the defence of another species may reflect the unique symbiotic relationship between anemonefishes and their hosts.

Limited possibilities for prezygotic barriers in the reproductive behaviour of sympatric Ophthalmotilapia species (Teleostei, Cichlidae)

Since prezygotic rather than postzygotic barriers are believed to maintain the diversity of closely related sympatric cichlids, differences in phenotypic traits and reproductive behaviours are likely involved in maintaining species boundaries. Here, we focused on the reproductive behaviour of three Ophthalmotilapia species with distributions that only overlap on a small stretch of the shore line of Lake Tanganyika. Repeated introgression of mitochondrial DNA between these species was previously reported, which suggested they can hybridise. Our aim is to test the hypothesis that reproductive behaviour acts as a prezygotic barrier that prevents frequent hybridisation in sympatric Ophthalmotilapia species. We performed a quantitative analysis of twelve reproductions (four for O. ventralis, six for O. nasuta, one for O. boops, and one between a female O. ventralis and a male O. nasuta). Although similar ethograms were obtained for these reproductions, the O. ventralis and O. boops males displayed a behaviour that was never performed by O. nasuta males. This behaviour was displayed during courtship and we called it 'invite'. In O. ventralis, we could show that it was associated with the emission of a single pulse sound. The comparison of O. nasuta and O. ventralis reproductive behaviours also revealed some quantitative differences: O. ventralis males showed the location of the bower more often to the female, whereas O. ventralis females followed the male more often. The similarity between the reproductive behaviours in O. ventralis and O. nasuta could explain the occurrence of the heterospecific spawning event recorded between an O. nasuta male and an O. ventralis female. Importantly, few eggs were laid and the maternal mouthbrooding that resulted from this heterospecific reproduction only lasted for two days, which suggested the abortion of egg development. Hence, in the absence of conspecifics, courtship and mating behaviours alone do not constitute perfect prezygotic barriers between these two species.

Fighting Nemo: Effect of 17α-ethinylestradiol (EE2) on aggressive behavior and social hierarchy of the false clown anemonefish Amphiprion ocellaris

Aggressive behavior is crucial for maintaining social hierarchy in anemonefish. Endocrine disrupting chemicals such as EE2 may affect fish social hierarchy via disrupting their aggression. In this study, we aimed to characterize the effects of 17α-ethinylestradiol (EE2) on aggressive behavior and social hierarchy in the false clown anemonefish (Amphiprion ocellaris). In the laboratory experiment, juvenile anemonefish were randomly distributed to separated tanks to form small colonies of three individuals and were fed with EE2-dosed diet (100ng/g food) or a control diet for 90d. Through the experiment, each tank was videotaped and behavioral indicators of social status, including aggressive behavior, submissive response, and shelter utilization, were quantitatively analyzed from the videos. The EE2 exposure caused a higher frequency of intra-colonial aggressive interactions and a less stable social hierarchy. Our findings demonstrate the importance of examining the effects of endocrine disrupting chemicals on the social behavior of coral reef fish.

Sound iconicity of abstract concepts: Place of articulation is implicitly associated with abstract concepts of size and social dominance

The concept of sound iconicity implies that phonemes are intrinsically associated with non-acoustic phenomena, such as emotional expression, object size or shape, or other perceptual features. In this respect, sound iconicity is related to other forms of cross-modal associations in which stimuli from different sensory modalities are associated with each other due to the implicitly perceived correspondence of their primal features. One prominent example is the association between vowels, categorized according to their place of articulation, and size, with back vowels being associated with bigness and front vowels with smallness. However, to date the relative influence of perceptual and conceptual cognitive processing on this association is not clear. To bridge this gap, three experiments were conducted in which associations between nonsense words and pictures of animals or emotional body postures were tested. In these experiments participants had to infer the relation between visual stimuli and the notion of size from the content of the pictures, while directly perceivable features did not support–or even contradicted–the predicted association. Results show that implicit associations between articulatory-acoustic characteristics of phonemes and pictures are mainly influenced by semantic features, i.e., the content of a picture, whereas the influence of perceivable features, i.e., size or shape, is overridden. This suggests that abstract semantic concepts can function as an interface between different sensory modalities, facilitating cross-modal associations.

Cohabitation promotes high diversity of clownfishes in the Coral Triangle

Global marine biodiversity peaks within the Coral Triangle, and understanding how such high diversity is maintained is a central question in marine ecology. We investigated broad-scale patterns in the diversity of clownfishes and their host sea anemones by conducting 981 belt-transects at 20 locations throughout the Indo-Pacific. Of the 1508 clownfishes encountered, 377 fish occurred in interspecific cohabiting groups and cohabitation was almost entirely restricted to the Coral Triangle. Neither the diversity nor density of host anemone or clownfish species alone influenced rates of interspecific cohabitation. Rather cohabitation occurred in areas where the number of clownfish species exceeds the number of host anemone species. In the Coral Triangle, cohabiting individuals were observed to finely partition their host anemone, with the subordinate species inhabiting the periphery. Furthermore, aggression did not increase in interspecific cohabiting groups, instead dominant species were accepting of subordinate species. Various combinations of clownfish species were observed cohabiting (independent of body size, phylogenetic relatedness, evolutionary age, dentition, level of specialization) in a range of anemone species, thereby ensuring that each clownfish species had dominant reproductive individuals in some cohabiting groups. Clownfishes are obligate commensals, thus cohabitation is an important process in maintaining biodiversity in high diversity systems because it supports the persistence of many species when host availability is limiting. Cohabitation is a likely explanation for high species richness in other obligate commensals within the Coral Triangle, and highlights the importance of protecting these habitats in order to conserve unique marine biodiversity.

Interspecific variation of warning calls in piranhas: a comparative analysis

Fish sounds are known to be species-specific, possessing unique temporal and spectral features. We have recorded and compared sounds in eight piranha species to evaluate the potential role of acoustic communication as a driving force in clade diversification. All piranha species showed the same kind of sound-producing mechanism: sonic muscles originate on vertebrae and attach to a tendon surrounding the bladder ventrally. Contractions of the sound-producing muscles force swimbladder vibration and dictate the fundamental frequency. It results the calling features of the eight piranha species logically share many common characteristics. In all the species, the calls are harmonic sounds composed of multiple continuous cycles. However, the sounds of Serrasalmus elongatus (higher number of cycles and high fundamental frequency) and S. manueli (long cycle periods and low fundamental frequency) are clearly distinguishable from the other species. The sonic mechanism being largely conserved throughout piranha evolution, acoustic communication can hardly be considered as the main driving force in the diversification process. However, sounds of some species are clearly distinguishable despite the short space for variations supporting the need for specific communication. Behavioural studies are needed to clearly understand the eventual role of the calls during spawning events.

New insights into the role of the pharyngeal jaw apparatus in the sound-producing mechanism of Haemulon flavolineatum (Haemulidae)

Grunts are fish that are well known to vocalize, but how they produce their grunting sounds has not been clearly identified. In addition to characterizing acoustic signals and hearing in the French grunt Haemulon flavolineatum, the present study investigates the sound-production mechanism of this species by means of high-speed X-ray videos and scanning electron microscopy of the pharyngeal jaw apparatus. Vocalizations consist of a series of stridulatory sounds: grunts lasting ~47 ms with a mean period of 155 ms and a dominant frequency of ~700 Hz. Auditory capacity was determined to range from 100 to 600 Hz, with greatest sensitivity at 300 Hz (105.0±11.8 dB re. 1 μPa). This suggests that hearing is not tuned exclusively to detect the sounds of conspecifics. High-speed X-ray videos revealed how pharyngeal jaws move during sound production. Traces of erosion on teeth in the fourth ceratobranchial arch suggest that they are also involved in sound production. The similarity of motor patterns of the upper and lower pharyngeal jaws between food processing and sound production indicates that calling is an exaptation of the food-processing mechanism.

Trait decoupling promotes evolutionary diversification of the trophic and acoustic system of damselfishes

Trait decoupling, wherein evolutionary release of constraints permits specialization of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal diversity. However, few empirical tests of this hypothesis exist. A central prediction, that the tempo of morphological evolution and ecological diversification should increase following decoupling events, remains inadequately tested. In damselfishes (Pomacentridae), a ceratomandibular ligament links the hyoid bar and lower jaws, coupling two main morphofunctional units directly involved in both feeding and sound production. Here, we test the decoupling hypothesis by examining the evolutionary consequences of the loss of the ceratomandibular ligament in multiple damselfish lineages. As predicted, we find that rates of morphological evolution of trophic structures increased following the loss of the ligament. However, this increase in evolutionary rate is not associated with an increase in trophic breadth, but rather with morphofunctional specialization for the capture of zooplanktonic prey. Lineages lacking the ceratomandibular ligament also shows different acoustic signals (i.e. higher variation of pulse periods) from others, resulting in an increase of the acoustic diversity across the family. Our results support the idea that trait decoupling can increase morphological and behavioural diversity through increased specialization rather than the generation of novel ecotypes.

Behaviours associated with acoustic communication in Nile tilapia (Oreochromis niloticus)

Background

Sound production is widespread among fishes and accompanies many social interactions. The literature reports twenty-nine cichlid species known to produce sounds during aggressive and courtship displays, but the precise range in behavioural contexts is unclear. This study aims to describe the various Oreochromis niloticus behaviours that are associated with sound production in order to delimit the role of sound during different activities, including agonistic behaviours, pit activities, and reproduction and parental care by males and females of the species.

Methodology/Principal Findings

Sounds mostly occur during the day. The sounds recorded during this study accompany previously known behaviours, and no particular behaviour is systematically associated with sound production. Males and females make sounds during territorial defence but not during courtship and mating. Sounds support visual behaviours but are not used alone. During agonistic interactions, a calling Oreochromis niloticus does not bite after producing sounds, and more sounds are produced in defence of territory than for dominating individuals. Females produce sounds to defend eggs but not larvae.

Conclusion/Significance

Sounds are produced to reinforce visual behaviours. Moreover, comparisons with O. mossambicus indicate two sister species can differ in their use of sound, their acoustic characteristics, and the function of sound production. These findings support the role of sounds in differentiating species and promoting speciation. They also make clear that the association of sounds with specific life-cycle roles cannot be generalized to the entire taxa.