Passive acoustic monitoring (PAM) is a powerful tool for studying ecosystems. However, its effective application in tropical environments, particularly for insects, poses distinct challenges. ...Neotropical katydids produce complex species-specific calls, spanning mere milliseconds to seconds and spread across broad audible and ultrasonic frequencies. However, subtle differences in inter-pulse intervals or central frequencies are often the only discriminatory traits. These extremities, coupled with low source levels and susceptibility to masking by ambient noise, challenge species identification in PAM recordings. This study aimed to develop a deep learning-based solution to automate the recognition of 31 katydid species of interest in a biodiverse Panamanian forest with over 80 katydid species. Besides the innate challenges, our efforts were also encumbered by a limited and imbalanced initial training dataset comprising domain-mismatched recordings. To overcome these, we applied rigorous data engineering, improving input variance through controlled playback re-recordings and by employing physics-based data augmentation techniques, and tuning signal-processing, model and training parameters to produce a custom well-fit solution. Methods developed here are incorporated into Koogu, an open-source Python-based toolbox for developing deep learning-based bioacoustic analysis solutions. The parametric implementations offer a valuable resource, enhancing the capabilities of PAM for studying insects in tropical ecosystems. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.
•There are important gaps in our understanding about the role of adaptation in speciation.•To fill these gaps, we clarify and define differences between sexual and natural selection.•We further ...clarify variation in models of sexual selection, a source of perennial confusion to biologists.•Sexual and natural selection likely interact during the evolution of reproductive isolation.•We provide a conceptual framework for testing hypotheses about the relative significance of sexual and natural selection in speciation.•Progress in speciation research will be made by testing the relative significance of natural and sexual selection in the evolution of premating reproductive isolation.
Speciation by divergent natural selection is well supported. However, the role of sexual selection in speciation is less well understood due to disagreement about whether sexual selection is a mechanism of evolution separate from natural selection, as well as confusion about various models and tests of sexual selection. Here, we outline how sexual selection and natural selection are different mechanisms of evolutionary change, and suggest that this distinction is critical when analyzing the role of sexual selection in speciation. Furthermore, we clarify models of sexual selection with respect to their interaction with ecology and natural selection. In doing so, we outline a research agenda for testing hypotheses about the relative significance of divergent sexual and natural selection in the evolution of reproductive isolation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The large body of theory on speciation with gene flow has brought to light fundamental differences in the effects of two types of mating rules on speciation: preference/trait rules, in which ...divergence in both (female) preferences and (male) mating traits is necessary for assortment, and matching rules, in which individuals mate with like individuals on the basis of the presence of traits or alleles that they have in common. These rules can emerge from a variety of behavioral or other mechanisms in ways that are not always obvious. We discuss the theoretical properties of both types of rules and explain why speciation is generally thought to be more likely under matching rather than preference/trait rules. We furthermore discuss whether specific assortative mating mechanisms fall under a preference/trait or matching rule, present empirical evidence for these mechanisms, and propose empirical tests that could distinguish between them. The synthesis of the theoretical literature on these assortative mating rules with empirical studies of the mechanisms by which they act can provide important insights into the occurrence of speciation with gene flow. Finally, by providing a clear framework we hope to inspire greater alignment in the ways that both theoreticians and empiricists study mating rules and how these rules affect speciation through maintaining or eroding barriers to gene flow among closely related species or populations.
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A limitation in bioacoustic studies has been the inability to differentiate individual sonic contributions from group‐level dynamics. We present a novel application of acoustic camera technology to ...investigate how individual wood frogs’ calls influence chorus properties, and how variation influences mating opportunities. We recorded mating calls and used playback trials to gauge preference for different chorus types in the laboratory. Males and females preferred chorus playbacks with low variance in dominant frequency. Females preferred choruses with low mean peak frequency. Field studies revealed more egg masses laid in ponds where males chorused with low variance in dominant frequency. We also noted a trend towards more egg masses laid in ponds where males called with low mean frequency. Nearest‐neighbour distances influenced call timing (neighbours called in succession) and distances increased with variance in chorus frequency. Results highlight the potential fitness implications of individual‐level contributions to a bioacoustic signal produced by groups.
It is often challenging to measure individual variation in an acoustic signal that is produced by large choruses or groups. We use a novel acoustic camera technology to simplify the solution to this challenge. We show that individual contributions to these choruses likely influences variation in mating success.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Night-time light can have profound ecological effects, even when the source is natural moonlight. The impacts of light can, however, vary substantially by taxon, habitat and geographical region. We ...used a custom machine learning model built with the Python package
to investigate the
effects of moonlight on the calling activity of neotropical forest katydids over multiple years. We prioritised species with calls that were commonly detected in human annotated data, enabling us to evaluate model performance. We focused on eight species of katydids that the model identified with high precision (generally greater than 0.90) and moderate-to-high recall (minimum 0.35), ensuring that detections were generally correct and that many calls were detected. These results suggest that moonlight has modest effects on the amount of calling, with the magnitude and direction of effect varying by species: half of the species showed positive effects of light and half showed negative. These findings emphasize the importance of understanding natural history for anticipating how biological communities respond to moonlight. The methods applied in this project highlight the emerging opportunities for evaluating large quantities of data with machine learning models to address ecological questions over space and time. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.
The evolution of mate preferences can be critical for the evolution of reproductive isolation and speciation. Heterospecific interference may carry substantial fitness costs and result in preferences ...where females are most responsive to the mean conspecific trait with low response to traits that differ from this value. However, when male traits are unbounded by heterospecifics, there may not be selection against females that respond to extreme trait values in the unbounded direction. To test how heterospecifics affected the shape of female response functions, I presented female Oecanthus tree crickets with synthetic calls representing a range of male calls, then measured female phonotaxis to construct response functions. The species with the fastest pulse rates in the community consistently responded to pulse rates faster than those produced by their males, whereas in the intermediate and slowest pulse rate species there was no significant difference between the male trait and the female response. This work suggests that species with the most extreme signal in the community respond to a greater range of signals, potentially resulting in a higher probability of hybridization during secondary contact, and revealing interactions between mate recognition and other aspects of sexual selection.
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Objective/Hypothesis
We explored the following hypotheses in a cohort of patients undergoing injection laryngoplasty: (1) glottic insufficiency affects voluntary cough airflow dynamics and restoring ...glottic competence may improve parameters of cough strength, (2) cough strength can be inferred from cough acoustic signal, and (3) glottic competence changes cough sounds and correlates with spectrogram morphology.
Study Type/Design
Prospective interventional study.
Methods
Subjects with glottic insufficiency secondary to unilateral vocal fold paresis, paralysis, or atrophy, and scheduled for injection laryngoplasty completed an instrumental assessment of voluntary cough airflow using a pneumotachometer and a protocolized voluntary cough sound recording. A Wilcoxon signed‐rank test was used to compare the differences between pre‐ and post‐injection laryngoplasty in airflow and acoustic measures. A Spearman rank‐order correlation was used to evaluate the association between airflow and acoustic cough measures.
Results
Twenty‐five patients (13F:12M, mean age 68.8) completed voluntary cough airflow measurements and 22 completed cough sound recordings. Following injection laryngoplasty, patients had a statistically significant decreased peak expiratory flow rise time (PEFRT) (mean change: −0.03 s, SD: 0.06, p = 0.04) and increased cough volume acceleration (mean change: 13.1 L/s2, SD: 33.9, p = 0.03), suggesting improved cough effectiveness. Correlation of cough acoustic measures with airflow measures showed a weak relationship between PEFRT and acoustic energy (coefficient: −0.31, p = 0.04) and peak power density (coefficient: −0.35, p = 0.02).
Conclusions
Our study thus indicates that injection laryngoplasty may help avert aspiration in patients with glottic insufficiency by improving cough effectiveness and that improved cough airflow measures may be tracked with cough sounds.
Level of Evidence
3 Laryngoscope, 133:S1–S14, 2023
We explored the following hypotheses in a cohort of patients undergoing injection laryngoplasty: (1) glottic insufficiency affects voluntary cough airflow dynamics and restoring glottic competence may improve parameters of cough strength, (2) cough strength can be inferred from cough acoustic signal, and (3) glottic competence changes cough sounds and correlates with spectrogram morphology. Our study thus indicates that injection laryngoplasty may help avert aspiration in patients with glottic insufficiency by improving cough effectiveness and that improved cough airflow measures may be tracked with cough sounds.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Predation produces intense selection and a diversity of defences. Reactive defences are triggered by predator cues, whereas proactive defences are always in effect. We assess whether prey rely on ...proactive defences when predator cues do not correlate well with predation risk. Many bats use echolocation to hunt insects, and many insects have evolved to hear bats. However, in species-rich environments like Neotropical forests, bats have extremely diverse foraging strategies, and the presence of echolocation corresponds only weakly to the presence of predators. We assess whether katydids that live in habitats with many non-dangerous bat species stop calling when exposed to echolocation. For 11 species of katydids, we quantified behavioural and neural responses to predator cues, and katydid signalling activity over 24 h periods. Despite having the sensory capacity to detect predators, many Neotropical forest katydids continued calling in the presence of predator cues, displaying proactive defences instead (short, infrequent calls totalling less than 2 cumulative seconds of sound per 24 h). Neotropical katydid signalling illustrates a fascinating case where trophic interactions are probably mediated by a third group: bats with alternative foraging strategies (e.g. frugivory). Although these co-occurring bats are not trophically connected, their mere presence disrupts the correlation between cue and predation risk.
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Communication is vital to the survival and reproductive success of organisms. There is growing evidence that anthropogenic noise interferes with acoustic communication. While recent studies have ...tested whether signallers behaviourally modify their signals to prevent masking from noise, studies have only recently begun to test whether noise in fact interferes with the perception of acoustic signals. In this study, we investigated how road noise affects both male signalling and female phonotaxis in Oecanthus tree crickets. Acoustic signals of tree crickets, which are relatively low amplitude and composed primarily of low frequencies, are likely to be masked by road noise. To determine whether males alter their calls in the presence of road noise, we assessed how a playback of recorded road noise changed four male calling characteristics: dominant frequency, call amplitude, total time spent calling and latency to begin calling. We then used response trials to test the ability of females to localize and respond to male calls in the presence of road noise. Unlike studies in other organisms, which detected quantifiable differences in male signal characteristics, male tree crickets were less likely to call but did not change signal characteristics. Surprisingly, female response to male signals was not affected by the presence of road noise, despite the potential masking effects of road noise. Because tree crickets often communicate in environments with many species of calling insects, tree crickets may be adapted to tolerate novel sources of acoustic interference. This study presents a case where male signals and female responses are not affected by road noise. Since species are differentially affected by noise, detailed understanding of behaviour and sensory systems may be necessary for predicting the effect of acoustic interference on trophic interactions and population dynamics.
•We examined effects of road noise on male signalling and female phonotaxis in tree crickets.•Males were less likely to begin calling in the presence of road noise.•Pulse rate, frequency and amplitude of male calls did not change in response to noise.•In laboratory trials, female response to male signals was not affected by road noise level.•Tree crickets showed an unaltered yet effective communication system in road noise.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Understanding the ecology and evolution of animal communication systems requires detailed data on signal structure and variation across species. Here, we describe the male acoustic signals of 50 ...species of Neotropical katydids (Orthoptera: Tettigoniidae) from Panama, with the goal of providing data and recordings for future research on katydid communication, evolution, ecology, and conservation. Male katydids were recorded individually using an ultrasound-sensitive microphone and high-sampling rate data acquisition board to capture both audible and ultrasonic components of calls. Calls varied enormously in duration, temporal patterning, peak frequency, and bandwidth both across and within subfamilies. We confirm previous studies showing that katydid species within the subfamily Pseudophyllinae produced short calls (<250 ms) at long intervals and we confirm that this is true for species in the subfamily Phaneropterinae as well. Species in the Conocephalinae, on the other hand, typically produced highly repetitive calls over longer periods of time. However, there were exceptions to this pattern, with a few species in the Conocephalinae producing very short calls at long intervals, and some species in the Phaneropterinae producing relatively long calls (1–6 s) or calling frequently. Our results also confirm previous studies showing a relationship between katydid size and the peak frequency of the call, with smaller katydids producing higher frequency calls, but the slope of this relationship differed with subfamily. We discuss the value of documenting the diversity in katydid calls for both basic studies on the ecology, evolution, and behavior of these species as well as the potential conservation benefits for bioacoustics monitoring programs.
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