Combinatorial signal processing in an insect

Human language is combinatorial: phonemes are grouped into syllables, syllables are grouped into words, and so on. The capacity for combinatorial processing is present, in different degrees, in some mammals and birds. We used vibrational insects, Enchenopa treehoppers, to test the hypothesis of basic combinatorial processing against two competing hypotheses: beginning rule (where the early signal portions play a stronger role in acceptability) and no ordering rule (where the order of signal elements plays no role in signal acceptability). Enchenopa males use plant-borne vibrational signals that consist of a whine followed by pulses. We tested the above hypotheses with vibrational playback experiments in which we presented Enchenopa females with stimuli varying in signal element combinations. We monitored female responses to these playbacks with laser vibrometry. We found strong support for combinatorial processing in Enchenopa: in brief, females preferred natural-combination signals regardless of the beginning element and discriminated against reverse-order signals or individual elements. Finding support for the combinatorial rule hypothesis in insects suggests that this capability represents a common solution to the problems presented by complex communication.Publisher PDFPeer reviewe

Acoustic species distribution models (aSDMs): A framework to forecast shifts in calling behaviour under climate change

Species distribution models (SDMs) are a key tool for biogeography and climate change research, although current approaches have some significant drawbacks. The use of species occurrence constrains predictions of correlative models, while there is a general lack of eco-physiological data to develop mechanistic models. Passive acoustic monitoring is an emerging technique in ecology that may help to overcome these limitations. By remotely tracking animal behaviour across species geographical ranges, researchers can estimate the climatic breadth of species activity and provide a baseline for refined predictive models. However, such integrative approach still remains to be developed. Here, we propose the following: (a) a general and transferable method to build acoustic SDMs, a novel tool combining acoustic and biogeographical information, (b) a detailed comparison with standard correlative and mechanistic models, (c) a step-by-step guide to develop aSDMs and (d) a study case to assess their effectiveness and illustrate model outputs, using a year-round monitoring of calling behaviour of the Iberian tree frog at the thermal extremes of its distribution range. This method aims at forecasting changes in environmental suitability for acoustic communication, a key and climate-dependent behaviour for a wide variety of animal taxa. aSDMs identified strong associations between calling behaviour and local environmental conditions and showed robust and consistent predictive performance using two alternative models (regression and boundary). Furthermore, these models better captured climatic variation than correlative models as they use observations at higher temporal resolution. These results support aSDMs as efficient tools to model calling behaviour under future climate scenarios. The proposed approach offers a promising basis to explore the capacity of vocal species to deal with climate change, supported by an innovative integration of two disciplines: bioacoustics and biogeography. aSMDs are grounded on ecologically realistic conditions and provide spatially and temporally explicit predictions on calling behaviour, with direct implications in reproduction and survival. This enables to precisely forecast shifts in breeding phenology, geographic distribution or species persistence. Our study demonstrates how acoustic monitoring may represent an increasingly valuable tool for climate change researchConsejería de Educación e Investigación, Grant/Award Number: 2020-T1/AMB20636 and 2017-T2/AMB-6035; European Commission, Grant/Award Number: EAVESTROP-661408; Ministerio de Economía, Industria y Competitividad, Grant/Award Number: CGL2017-88764-

Freshwater ecoacoustics as a tool for continuous ecosystem monitoring

Copyright by the Ecological Society of AmericaPassive acoustic monitoring is gaining popularity in ecology as a practical and non-invasive approach to surveying ecosystems. This technique is increasingly being used to monitor terrestrial systems, particularly bird populations, given that it can help to track temporal dynamics of populations and ecosystem health without the need for expensive resampling. We suggest that underwater acoustic monitoring presents a viable, non-invasive, and largely unexplored approach to monitoring freshwater ecosystems, yielding information about three key ecological elements of aquatic environments – (1) fishes, (2) macroinvertebrates, and (3) physicochemical processes – as well as providing data on anthropogenic noise levels. We survey the literature on this approach, which is substantial but scattered across disciplines, and call for more cross-disciplinary work on recording and analysis techniques. We also discuss technical issues and knowledge gaps, including background noise, spatiotemporal variation, and the need for centralized reference collection repositories. These challenges need to be overcome before the full potential of passive acoustics in dynamic detection of biophysical processes can be realized and used to inform conservation practitioners and managers

Passive acoustic monitoring provides a fresh perspective on fundamental ecological questions

Passive acoustic monitoring (PAM) has emerged as a transformative tool for applied ecology, conservation and biodiversity monitoring, but its potential contribution to fundamental ecology is less often discussed, and fundamental PAM studies tend to be descriptive, rather than mechanistic. Here, we chart the most promising directions for ecologists wishing to use the suite of currently available acoustic methods to address long-standing fundamental questions in ecology and explore new avenues of research. In both terrestrial and aquatic habitats, PAM provides an opportunity to ask questions across multiple spatial scales and at fine temporal resolution, and to capture phenomena or species that are difficult to observe. In combination with traditional approaches to data collection, PAM could release ecologists from myriad limitations that have, at times, precluded mechanistic understanding. We discuss several case studies to demonstrate the potential contribution of PAM to biodiversity estimation, population trend analysis, assessing climate change impacts on phenology and distribution, and understanding disturbance and recovery dynamics. We also highlight what is on the horizon for PAM, in terms of near-future technological and methodological developments that have the potential to provide advances in coming years. Overall, we illustrate how ecologists can harness the power of PAM to address fundamental ecological questions in an era of ecology no longer characterised by data limitation

Ecologie et diversité acoustique des milieux aquatiques : exploration en milieux tempérés

An important diversity of animal species produces sounds during commu- nication, orientation, movement, or prey-predator acts. These sounds are not distributed randomly in space and time and are therefore thought to follow assembly rules forming either acoustic populations or acoustic communities. Freshwater environments, and ponds in particular, are considered as primary resources for biological diversity and as such host a potentially significant number of soniferous species. However the acoustic diversity of these natural environments remains totally unexplored. The main aim of this PhD was to explore for the first time the acoustic diversity found in temperate freshwater by studying the patterns and structural processes of a selection of acoustic populations and communities recored in several types of freshwater environments. A review of the literature on sound production by freshwater organisms along with laboratory recordings of target species revealed that a valuable acoustic diversity can be found in temperate freshwater environments. To understand how the acoustic diversity is structured, the acoustic communities of three temperate ponds were acoustically monitored. This study revealed that the three ponds were characterised by rich and distinct acoustic communities with specific spatio-temporal dynamics. To further understand the potential factors structuring freshwater acoustic communities, environmental variables were assessed along with the composition of acoustic communities found in six secondary channels of the Rhône riverine floodplain. Two environmental variables were investigated: the water temperature and the level of lateral connectivity of the secondary channels to the main river. Acoustic communities in the Rhône riverine floodplain were clearly struc- tured by lateral connectivity suggesting a role of this key variable as an assembly rule. Finally to understand the possible processes linking animal acoustics and the natural en- vironment, a population of aquatic insect, Micronecta scholtzi, was acoustically monitored in a Mediterranean pond. The level of M. scholtzi acoustic activity was assessed continuously using a network of twelve synchronised acoustic sensors. The acoustic activity of M. scholtzi showed a regular daily pattern that was modified in amplitude and phase by the playback of an anthropogenic noise. This experiment revealed that the effects of noise pollution may emerge at an aquatic insect population level. This PhD unraveled the existence of a significant amount of unexplored acoustic diversity in freshwater environments and identified links between acoustics and the environment. This research opens interesting perspectives in the use of acoustic to tackle fundamental and applied ecological questions in freshwater environments.Une grande diversité d’animaux produit des sons pour communiquer, s’orienter, ou lors de la réalisation d’actes comportementaux comme la prise de nourriture. Ces sons ne se répartissent pas aléatoirement dans l’espace et le temps suggérant l’existence de règles d’assemblage sonore qui structurent les populations et communautés acoustiques. Les environnements d’eau douce, et en particulier les mares, sont consid- érés comme les réservoirs d’une importante diversité biologique, et donc potentiellement abritant un nombre significatif d’espèces produisant des sons. Cependant la diversité acoustique de ces milieux naturels n’a jamais été explorée. L’objectif principal de cette thèse est d’explorer pour la première fois la diversité acoustique présente dans les milieux d’eau douce en climat tempéré en étudiant les struc- tures des populations et communautés acoustiques et en explorant les processus pouvant déterminer ces structures. Une revue bibliographique sur la production sonore par les organismes d’eau douce ainsi que des enregistrements d’espèces cibles effectués en laboratoire révèlent qu’une diversité acoustique particulière existe dans les environnements d’eau douce en milieux tempérés. Pour comprendre comment cette diversité est structurée, les communautés acoustiques de trois mares situées dans des environnements différents ont été enregistrées et suivies au cours du temps. Cette étude révèle que les trois mares sont caractérisées par des communautés acoustiques riches et distinctes ayant des dynamiques spatio-temporelles spécifiques. Les facteurs potentiels structurant les communautés acoustiques d’eau douce ont été recherchés en testant si la composition de communautés acoustiques dans six bras morts de la plaine d’inondation du Rhône était liée à des variables environnementales. Nos résultats montrent que les communautés acoustiques des bras morts sont significativement liés à une variable environnementale: le degré de connectivité entre les bras morts et le lit principal de la rivière. Ce résultat suggère un rôle clé de cette variable dans les règles d’assemblage des communautés. Enfin, pour comprendre les processus possibles liant la production de sons et l’environnement naturel, une population de l’insecte aqua- tique Micronecta scholtzi a été suivie par des enregistrements acoustiques dans une mare méditerranéenne. Le niveau d’activité acoustique de M. scholtzi a été estimé de façon continue à l’aide d’un réseau de 12 capteurs sonores synchronisés. L’activité acoustique était caractérisée par un rythme circadien, dont les propriétés étaient perturbées par la diffusion expérimentale d’un bruit d’origine anthropique. Cette expérience révèle que les effets de la pollution sonore peuvent être observés à l’échelle d’une population d’insectes aquatiques. Ce travail montre ainsi l’existence d’une diversité acoustique dans les milieux d’eau douce et identifie des relations entre production acoustique et facteurs environnementaux. Ce travail ouvre également des perspectives intéressantes d’utilisation de l’acoustique pour aborder des problématiques d’écologie fondamentale et appliquée en milieu d’eau douce

Acoustic communities reflects lateral hydrological connectivity in riverine floodplain similarly to macroinvertebrate communities

Funding: This project was supported by a fieldwork grant from the LabEx BCDiv, an ENS PhD grant (CD), and a Post-doctoral grant from the Fondation Fyssen (DL). Acquisition of community data was partly funded by the scientific monitoring of the Rhone River restoration funded by the “Compagnie Nationale du Rhône”, “Agence de l’Eau Rhône-Méditerranée-Corse” and “Région Rhône-Alpes”.Recent studies revealed that information on ecological patterns and processes can be investigated using sounds emanating from animal communities. In freshwater environments, animal communities are strongly shaped by key ecological factors such as lateral connectivity and temperature. We predict that those ecological factors are linked to acoustic communities formed by the collection of sounds emitted underwater. To test this prediction, we deployed a passive acoustic monitoring during 15 days in six floodplain channels of the European river Rhône. The six channels differed in their temperature and level of lateral connectivity to the main river. In parallel, we assessed the macroinvertebrate communities of these six channels using classical net sampling methods. A total of 128 sound types and 142 animal taxa were inventoried revealing an important underwater diversity. This diversity, instead of being randomly distributed among the six floodplain channels, was site-specific. Generalized mixed-effects models demonstrated a strong effect of both temperature and lateral connectivity on acoustic community composition. These results, congruent with macroinvertebrate community composition, suggest that acoustic communities reflect the interactions between animal communities and their environment. Overall our study strongly supports the perspectives offered by acoustic monitoring to describe and understand ecological patterns in freshwater environments.Publisher PDFPeer reviewe

The indirect genetic effect interaction coefficient ψ : theoretically essential and empirically neglected

Funding: N.W.B. was funded by the UK Natural Environment Research Council (NE/T000619/1, NE/L011255/1), and C.D. was funded by a US National Science Foundation award (award no. 1855962).The interaction effect coefficient ψ has been a much-discussed, fundamental parameter of indirect genetic effect (IGE) models since its formal mathematical description in 1997. The coefficient simultaneously describes the form of changes in trait expression caused by genes in the social environment and predicts the evolutionary consequences of those IGEs. Here, we report a striking mismatch between theoretical emphasis on ψ and its usage in empirical studies. Surveying all IGE research, we find that the coefficient ψ has not been equivalently conceptualized across studies. Several issues related to its proper empirical measurement have recently been raised, and these may severely distort interpretations about the evolutionary consequences of IGEs. We provide practical advice on avoiding such pitfalls. The majority of empirical IGE studies use an alternative variance-partitioning approach rooted in well-established statistical quantitative genetics, but several hundred estimates of ψ (from 15 studies) have been published. A significant majority are positive. In addition, IGEs with feedback, that is, involving the same trait in both interacting partners, are far more likely to be positive and of greater magnitude. Although potentially challenging to measure without bias, ψ has critically-developed theoretical underpinnings that provide unique advantages for empirical work. We advocate for a shift in perspective for empirical work, from ψ as a description of IGEs, to ψ as a robust predictor of evolutionary change. Approaches that "run evolution forward" can take advantage of ψ to provide falsifiable predictions about specific trait interactions, providing much-needed insight into the evolutionary consequences of IGEs.Publisher PDFPeer reviewe

Six steps towards operationalising freshwater ecoacoustic monitoring

1. Applications in bioacoustics and its sister discipline ecoacoustics have increased exponentially over the last decade. However, despite knowledge about aquatic bioacoustics dating back to the times of Aristotle and a vast amount of background literature to draw upon, freshwater applications of ecoacoustics have been lagging to date. 2. In this special issue, we present nine studies that deal with underwater acoustics, plus three acoustic studies on water-dependent birds and frogs. Topics include automatic detection of freshwater organisms by their calls, quantifying habitat change by analysing entire soundscapes, and detecting change in behaviour when organisms are exposed to noise. 3. We identify six major challenges and review progress through this special issue. Challenges include characterisation of sounds, accessibility of archived sounds as well as improving automated analysis methods. Study design considerations include characterisation analysis challenges of spatial and temporal variation. The final key challenge is the so far largely understudied link between ecological condition and underwater sound. 4. We hope that this special issue will raise awareness about underwater soundscapes as a survey tool. With a diverse array of field and analysis tools, this issue can act as a manual for future monitoring applications that will hopefully foster further advances in the field.</p

Spatio-temporal heterogeneity in river sounds:disentangling micro- and macro-variation in a chain of waterholes

International audience1. Passive acoustic monitoring is gaining momentum as a viable alternative method to surveying freshwater ecosystems. As part of an emerging field, the spatio-temporal replication levels of these sampling methods need to be standardized. However, in shallow waters, acoustic spatio-temporal patchiness remains virtually unexplored. 2. In this paper, we specifically investigate the spatial heterogeneity in underwater sounds observed within and between waterholes of an ephemeral river at different times of the day and how it could affect sampling in passive acoustic monitoring. 3. We recorded in the Einasleigh River, Queensland in August 2016, using a linear transect of hydrophones mounted on frames. We recorded four times a day: at dawn, midday, dusk and midnight. To measure different temporal and spectral attributes of the recorded sound, we investigated the mean frequency spectrum and computed acoustic indices. 4. Both mean frequency spectrum and index analyses revealed that the site and diel activity patterns significantly influenced the sounds recorded, even for adjacent sites with similar characteristics along a single river. We found that most of the variation was due to temporal patterns, followed by between-site differences, while within-site differences had limited influence. 5. This study demonstrates high spatio-temporal acoustic variability in freshwater environments, linked to different species or species groups. Decisions about sampling design are vital to obtain adequate representation. This study thus emphasizes the need to tailor spatio-temporal settings of a sampling design to the aim of the study, the species and the habitat