Adaptive Hypothesis Research Articles

Effect of commodity prices on financial soundness; insight from adaptive market hypothesis in the Ghanaian setting

Commodity revenue is a greater portion of total merchandise export in Ghana. Fluctuations in commodity prices directly and indirectly affect the financial soundness of an economy. Hence, we assessed the effect of commodity prices on banking sector's financial soundness indicators (BsFSI) under diverse market (bullish, normal and bearish) conditions. We employed monthly data on commodity prices and BsFSI from January 2007 to March 2022. We employed quantile regression and causality in quantile estimation techniques. The results from the quantile regression showed that commodity (cocoa, gold and crude oil) prices significantly affect Ghana's BsFSI at diverse market conditions asymmetrically. The specific predictive power noticed depends on the financial soundness indicator as well as the condition of the market. The results confirm the adaptive market hypothesis in the Ghanaian economy implying the inefficiency in the soundness of the financial sector. This allows traders and investors to adapt their strategies in response to changing financial sector conditions. Our findings are important to policy makers for the implementation of commodity price stabilisation schemes and hedging strategies while considering market conditions.

Changes in the acoustic structure of Australian bird communities along a habitat complexity gradient

Abstract Avian vocalizations have evolved in response to a variety of abiotic and biotic selective pressures. While there is some support for signal convergence in similar habitats that are attributed to adaptation to the acoustic properties of the environment (the “acoustic adaptation hypothesis,” AAH), there is also evidence for character displacement as a result of competition for signal space among coexisting species (the “acoustic niche partitioning hypothesis”). We explored the acoustic space of avian assemblages distributed along six different habitat types (from herbaceous habitats to warm rainforests) in southeastern Queensland, Australia. We employed three acoustic diversity indices (acoustic richness, evenness, and divergence) to characterize the signal space. In addition, we quantified the phylogenetic and morphological structure (in terms of both body mass and beak size) of each community. Acoustic parameters showed a moderately low phylogenetic signal, indicating labile evolution. Although we did not find meaningful differences in acoustic diversity indices among habitat categories, there was a significant relationship between the regularity component (evenness) and vegetation height, indicating that acoustic signals are more evenly distributed in dense habitats. After accounting for differences in species richness, the volume of acoustic space (i.e., acoustic richness) decreased as the level of phylogenetic and morphological resemblance among species in a given community increased. Additionally, we found a significantly negative relationship between acoustic divergence and divergence in body mass indicating that the less different species are in their body mass, the more different their songs are likely to be. This implies the existence of acoustic niche partitioning at a community level. Overall, while we found mixed support for the AAH, our results suggest that community-level effects may play a role in structuring acoustic signals within avian communities in this region. This study shows that signal diversity estimated by diversity metrics of community ecology based on basic acoustic parameters can provide additional insight into the structure of animal vocalizations.

Temperature and Turgor "Limitation" and Environmental "Control" in Xylem Biology and Dendrochronology.

Trees and other woody plants are immensely ecologically important, making it essential to understand the causes of relationships between tree structure and function. To help these efforts, we highlight persistent traditions in plant biology of appealing to environmental factors "limiting" or "controlling" woody plant features. Examples include the idea that inevitable drops in cell turgor with plant height limit cell expansion and thus leaf size and tree height; that low temperatures prohibit lignification of cells and thus the growth of woody plants at high elevation; and notions from dendrochronology and related fields that climate factors such as rainfall and temperature "control" growth ring features. We show that notions of "control," "limitation," and the like imply that selection would favor a given trait value, but that these would-be favored values are developmentally impossible to produce. Such "limitation" scenarios predict trait frequency distributions that are very narrow and are abruptly curtailed at the upper limit of developmental possibility (the right-hand side of the distribution). Such distributions have, to our knowledge, never been observed, so we see little empirical support for "limitation" hypotheses. We suggest that, as a more productive starting point, plant biologists should examine adaptation hypotheses, in which developmental possibility is wide (congruent with the wide ranges of trait variation that really are observed), but only some of the possible variants are favored. We suggest that (1) the traditional the proximate/ultimate causation distinction, (2) purging scenarios of teleology/anthropomorphism, and (3) stating hypotheses in terms of developmental potential and natural selection are three simple ways of making "limitation" hypotheses clearer with regard to biological process and thus empirically testable.

Variation in fruit and seed dimensions is better explained by dispersal system than by leaf size in a tropical rainforest.

Variation in fruit and seed traits could originate from selection pressures exerted by frugivores or other ecological factors (adaptive hypotheses) and developmental constraints (by-product hypotheses) or chance. We evaluated fruit and leaf traits for nearly 850 plant species from a rainforest in Tinigua Park, Colombia. Through a series of linear regressions controlling for the phylogenetic signal of the traits (minimum N = 542), we tested (1) whether the allometry between seed width and length depends on seed dispersal system (Mazer and Wheelwright's adaptive hypothesis of allometry for species dispersed in the guts of animals = endozoochory) and (2) whether fruit length is associated with leaf length (i.e., Herrera's by-product hypothesis derived from the assumption that both organs develop from homologous structures). We found a strong negative allometric association between seed width and length for seeds of endozoochorous species, as expected; but also, for anemochorous species. We found a positive relationship between fruit and leaf length, but this relationship was not evident for zoochorous species. Fruit size was highly correlated with seed size. The allometry between seed length and width varied among dispersal systems, supporting that fruit and seed morphology has been modified by interactions with frugivores and by the possibility to rotate for some wind dispersed species. We found some support for the hypothesis on developmental constraints because fruit and leaf size were positively correlated, but the predictive power of the relationship was low (10-15%).

Time-Varying and Scale-Dependent Informational Efficiency of the European CO2 Emissions Market: An Analysis Based on Singular Value Decomposition Entropy

This work examined the informational efficiency of the European CO2 emission trading market for the different implementation phases in the period 2008–2022:Q3. The approach is based on a bootstrap singular value decomposition (SVD) approach and the analysis was conducted for a rolling window to assess the time-varying efficiency and over different time scales. The impact of the COVID-19 lockdown and the Russia–Ukraine conflict was evaluated. The results showed that the informational efficiency changes over time and scales, which is in line with adaptive market hypothesis (AMH) notions. High market efficiency was exhibited in Phase II (2008–2012), but large deviations from efficiency, especially for quarterly scale, were exhibited in Phase III. However, Phase IV has shown a behavior consistent with informational efficiency. The COVID-19 outbreak negatively impacted informational efficiency. On the other hand, it seems that the Russia–Ukraine conflict has improved informational efficiency due to the European decisions to move to energy independence policies. The findings in this study suggest that the European carbon market is gradually attaining a state of financial maturity.

The multifactor pelvis: An alternative to the adaptationist approach of the obstetrical dilemma.

The obstetrical dilemma describes the competing demands that a bipedally adapted pelvis and a large-brained neonate place on human childbirth and is the predominant model within which hypotheses about the evolution of the pelvis are framed. I argue the obstetrical dilemma follows the adaptationist program outlined by Gould and Lewontin in 1979 and should be replaced with a new model, the multifactor pelvis. This change will allow thorough consideration of nonadaptive explanations for the evolution of the human pelvis and avoid negative social impacts from considering human childbirth inherently dangerous. First, the atomization of the pelvis into discrete traits is discussed, after which current evidence for both adaptive and nonadaptive hypotheses is evaluated, including childbirth, locomotion, shared genetics with other traits under selection, evolutionary history, genetic drift, and environmental and epigenetic influences on the pelvis.

Habitat and food preferences of European rabbits in core and edge populations along the invasion front Patagonia-Monte, Argentina.

The European rabbit Oryctolagus cuniculus is an exotic herbivorous mammal undergoing an active phase of geographical expansion in the arid ecosystems of Argentina. The Adaptive Flexibility Hypothesis states that populations at the range edge (new populations) will exhibit greater flexibility in the use of resources compared with populations located in the range core (older populations). The objective of this work was to compare the rabbit's use of spatial and trophic resources in relation to the establishment time of their populations. The sampling was carried out for 2 years (2017 and 2018) in sites with different establishment times for rabbit populations. Random sampling stratified by type of habitat was applied using 115 fixed strip transects of 1,000 m2 laid out across the study areas. Fresh rabbit signs were recorded in each transect, and environmental and anthropic variables were measured. Our results show that the individuals from the range edge are more selective in the use of habitat than those from the range core. At the microhabitat level, we observed a pattern in the particular components of habitat use by rabbits mainly linked to food availability and proximity to water. From a trophic perspective, rabbits could show flexible adjustment to novel conditions and environments in the range edge. The variability in resource use by the European rabbit confirms its ecological flexibility, pivotal for their advance toward new environments in Argentina.

Adaptive market hypothesis: A comparison of Islamic and conventional stock indices

We assess the informational efficiency of nine Dow Jones Islamic market indices and their counterpart conventional Morgan Stanley indices using data from 1996 to 2020. We test the martingale difference hypothesis of no return predictability over time and assess the adaptive market hypothesis over different market conditions. We find that the null is rejected in several periods in line with the adaptive market hypothesis for both Islamic and conventional stock indices. However, we do not observe any significant differences in return predictability between Islamic and conventional stocks in different market conditions, including the financial crisis of 2007–08 and the COVID-19 pandemic.

Historical Development of Frontier Stock Markets in Sub-Saharan Africa

Purpose: The purpose of this research is to review and compare the development of the three major frontier stock markets in Sub-Saharan Africa over time. The study provides some narrative around the historical development of each market as well as a theoretical backdrop for stock market development studies. Theoretical framework: The adaptive market hypothesis was used as the theoretical backdrop for the study. The adaptive market suggests that stock markets develop in an evolutionary manner (similar to natural selection). This evolution of stock market development is influenced by changes in investors’ behavior and regulatory standards. Design/methodology/approach: Data was collected from 1993 to 2020 on the IMF market efficiency score, the value of stocks traded, aggregate market capitalization, and the number of listed companies for the sample markets. The study used descriptive statistics and trend analysis to discuss and compare the stock market development indicators across the different selected frontier markets. Findings: The study discovered an improvement in stock market performance across the sample period. The Johannesburg Stock Exchange was found to be the most developed of the three stock exchanges. The Nigerian Stock Exchange was second while the Nairobi Stock Exchange was third. Some factors that erode the performance of these stock markets were also discussed. The practical and social implications: The sample stock markets are the major frontier markets, and so are often the first stop for foreign investors that want to penetrate the Sub-Saharan African markets. The performance of these markets often determines the level of foreign direct investment (FDI) and foreign portfolio investment (FPI) that flow into Africa. Originality/ Value: Few studies have investigated the performance of stock markets in Sub-Saharan Africa. Also, the few studies that investigate the performance of these markets rarely proceed to discuss the market-wide factors that erode the performance of these markets compared to those of developed economies. Some factors like the size of the economy, low financial literacy, misplaced government policies, poor investment culture, buy-and-hold-tight attitude, and high transaction costs were identified and discussed.

The Reproductive Capacities of the Calanoid Copepods Parvocalanus crassirostis and Acartia pacifica under Different pH and Temperature Conditions.

The increasing atmospheric CO2 concentrations and warming of marine waters have encouraged experiments on multi-stressor interactions in marine organisms. We conducted a multigenerational experiment to assess reproductive capacities regarding egg production in calanoid copepods Parvocalanus crassirostis and Acartia pacifica under different pH and temperature conditions. The experimental set-up allowed assessing the tandem effect of warming and acidification on the number of eggs produced by healthy copepod pairs under two pH conditions of 8.20 and 7.50 (hard selection) as well as with a gradual reduction of 0.05 pH units at each generation (soft selection). The results are quite interesting, with very diverse performance across temperatures. The number of eggs produced under hard selection was higher at pH 8.20 compared to pH 7.50 for both species, with the maximum number of eggs produced at 24-28 °C, whereas under soft selection, there was no significant difference in the egg production rate at 24-28 °C across generations and there was an improvement in the number of eggs produced at 8-16 °C. The results provide evidence that in a future ocean scenario of lower pH and higher temperature, the two species, and possibly the copepod population at large, might not decrease. Copepod populations might be resilient, and the transcriptomic evidence of adaptation to increased temperature and lower pH is a ray of hope. We believe further studies are needed to provide more robust datasets to underpin the hypothesis of adaptation to climate change.

Expansion processes of two emblematic Luehdorfia butterflies across the Japanese archipelago

AbstractAimAdaptation to local environments has been considered a driving force of ecological speciation. Previous phylogenetic studies at higher taxonomic levels have strongly suggested that herbivore diversification occurs through local adaptation to host plants. However, whether similar mechanisms contribute to within‐species diversification remains poorly understood. We reconstructed species expansion processes using the phylogenetic relationships between two Luehdorfia butterflies and their host plants and tested the local adaptation hypothesis during species diversification.LocationJapanese archipelago.TaxaLuehdorfia japonica and L. puziloi.MethodsWe analysed mitochondrial DNA and single‐nucleotide polymorphisms to trace the expansion processes of two species in the Japanese archipelago. We analysed data collected during trans‐host plant feeding experiments to test for local host plant adaptation in L. japonica.ResultsLuehdorfia japonica differentiated 17.0 million years ago (MYA) from a group of four Luehdorfia species in East Asia, and L. puziloi differentiated 13.3 MYA from the remaining three species. We observed several genetic groups in both species, reflecting geographical differences among populations. Some host plants had detrimental effects on the pupation rates of L. japonica, demonstrating the presence of genetic barriers between populations of this species.Main ConclusionsAlthough these two sibling species were influenced by the geological formation of the Japanese archipelago, their present population structures differ greatly: L. japonica expanded its distribution and adapted to local host plants along at least four expansion routes independent of host plant phylogeny, and L. puziloi exhibited a more isolated population structure and was less strongly influenced by gene flow among populations. These results suggest that both isolation by distance and isolation by adaptation have been important drivers resulting in the present‐day population structure of L. japonica. Unidirectional gene flow through local adaptation to the host plant may have played a role in initial speciation.

Testing trade‐offs in amphibian metamorphic traits: Swimming performance and selection across metamorphic stages in the aquatic frog Xenopus laevis

Abstract As frogs undergo metamorphosis from tadpole to adult, they may be susceptible to decreases in locomotor performance and survival during stages in which the tail and limbs are both present. Because these alternative axial and appendicular propulsive systems might interfere with each other, performance might be better when only one or the other system predominates. This framework, termed the ‘adaptive peak hypothesis’ emerged from studies of generalist anuran taxa with biphasic life histories in which aquatic larvae transition to terrestrial adults. However, it is not clear that such patterns apply to taxa with different patterns of ontogenetic environmental transitions. We evaluated the relationship between morphology, locomotor performance and survival versus predators across metamorphic stages of a fully aquatic frog, the pipid Xenopus laevis. We measured escape performance from individuals of four developmental stages spanning possession of just a tail, the presence of both tail and legs and resorption of the tail, and then conducted selection trials in which equal numbers of individuals of all stages were exposed to an aquatic predator (cichlid fish). After collecting survivors from these trials, we calculated linear and nonlinear selection gradients for a suite of morphological traits. Unlike generalist frogs, we found that both locomotor performance and survival increased across metamorphic stages of X. laevis. Linear selection gradients favoured tadpoles with longer hindlimbs, longer and narrower bodies, and shorter tails—patterns that generally parallel trends during metamorphic growth. Nonlinear selection showed that longer hindlimbs were favoured as body length increased and the positive effect of forelimb length was reduced as tail length increased. The relationship between hindlimb and body length aligns with expected changes in growth postmetamorphosis where postmetamorphic individuals are expected to have greater survival. However, longer forelimbs are generally associated with decreased locomotor performance, suggesting that alternative mechanisms of selection may be acting on the forelimbs of Xenopus through development. Overall, our results indicate that the generality of the adaptive peak framework, as applied to amphibian metamorphosis, can be impacted by specifics of life history patterns across species. Read the free Plain Language Summary for this article on the Journal blog.

Nonlinear changes in pupillary attentional orienting responses across the lifespan

The cognitive aging process is not necessarily linear. Central task-evoked pupillary responses, representing a brainstem-pupil relationship, may vary across the lifespan. Thus we examined, in 75 adults ranging in age from 19 to 86, whether task-evoked pupillary responses to an attention task may serve in as an index of cognitive aging. This is because the locus coeruleus (LC), located in the brainstem, is not only among the earliest sites of degeneration in pathological aging, but also supports both attentional and pupillary behaviors. We assessed brief, task-evoked phasic attentional orienting to behaviorally relevant and irrelevant auditory tones, stimuli known specifically to recruit the LC in the brainstem and evoke pupillary responses. Due to potential nonlinear changes across the lifespan, we used a novel data-driven analysis on 6 dynamic pupillary behaviors on 10% of the data to reveal cut off points that best characterized the three age bands: young (19–41 years old), middle aged (42–68 years old), and older adults (69 + years old). Follow-up analyses on independent data, the remaining 90%, revealed age-related changes such as monotonic decreases in tonic pupillary diameter and dynamic range, along with curvilinear phasic pupillary responses to the behaviorally relevant target events, increasing in the middle-aged group and then decreasing in the older group. Additionally, the older group showed decreased differentiation of pupillary responses between target and distractor events. This pattern is consistent with potential compensatory LC activity in midlife that is diminished in old age, resulting in decreased adaptive gain. Beyond regulating responses to light, pupillary dynamics reveal a nonlinear capacity for neurally mediated gain across the lifespan, thus providing evidence in support of the LC adaptive gain hypothesis.

Ecological factors drive the divergence of morphological, colour and behavioural traits in cactus wrens (Aves, Troglodytidae).

The study of ecological mechanisms influencing organisms' phenotypic variation is a central subject of evolutionary biology. In this study, we characterized morphological, plumage colour and acoustic variation in cactus wrens Campylorhynchus brunneicapillus throughout its distribution. We assessed whether Gloger's, Allen's and Bergmann's ecogeographical rules, and the acoustic adaptation hypothesis relate to geographical trait variation. We analysed specimen coloration in belly and crown plumage, beak shape and structural song characteristics. We tested whether the subspecific classification or the peninsular/mainland groups mirrored the geographical variation in phenotypes and whether ecological factors were associated with patterns of trait variation. Our results suggest that colour, beak shape and acoustic traits varied across the range, in agreement with two lineages described by genetics. The simple versions of Gloger's and Allen's rules are related to variations in colour traits and morphology. Conversely, patterns of phenotypic variation did not support Bergmann's rule. The acoustic adaptation hypothesis supported song divergence for frequency-related traits. Phenotypic variation supports the hypothesis of two taxa: C. affinis in the Baja California peninsula and C. brunneicapillus in the mainland. The ecological factors are associated with phenotypic trait adaptations, suggesting that divergence between lineages could result from ecological divergence.

Selection of an anti-pathogen skin microbiome following prophylaxis treatment in an amphibian model system.

With emerging diseases on the rise, there is an urgent need to identify and understand novel mechanisms of prophylactic protection in vertebrate hosts. Inducing resistance against emerging pathogens through prophylaxis is an ideal management strategy that may impact pathogens and their host-associated microbiome. The host microbiome is recognized as a critical component of immunity, but the effects of prophylactic inoculation on the microbiome are unknown. In this study, we investigate the effects of prophylaxis on host microbiome composition, focusing on the selection of anti-pathogenic microbes contributing to host acquired immunity in a model host-fungal disease system, amphibian chytridiomycosis. We inoculated larval Pseudacris regilla against the fungal pathogen Batrachochytrium dendrobatidis (Bd) with a Bd metabolite-based prophylactic. Increased prophylactic concentration and exposure duration were associated with significant increases in proportions of putatively Bd-inhibitory host-associated bacterial taxa, indicating a protective prophylactic-induced shift towards microbiome members that are antagonistic to Bd. Our findings are in accordance with the adaptive microbiome hypothesis, where exposure to a pathogen alters the microbiome to better cope with subsequent pathogen encounters. Our study advances research on the temporal dynamics of microbiome memory and the role of prophylaxis-induced shifts in microbiomes contributing to prophylaxis effectiveness. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.

Lexical prediction does not rationally adapt to prediction error: ERP evidence from pre-nominal articles

People sometimes predict upcoming words during language comprehension, but debate remains on when and to what extent such predictions indeed occur. The rational adaptation hypothesis holds that predictions develop with expected utility: people predict more strongly when predictions are frequently confirmed (low prediction error) rather than disconfirmed. However, supporting evidence is mixed thus far and has only involved measuring responses to supposedly predicted nouns, not to preceding articles that may also be predicted. The current, large-sample (N = 200) ERP study on written discourse comprehension in Dutch therefore employs the well-known ‘pre-nominal prediction effect’: enhanced N400-like ERPs for articles that are unexpected given a likely upcoming noun’s gender (i.e., the neuter gender article ‘het’ when people expect the common gender noun phrase ‘de krant’, the newspaper) compared to expected articles. We investigated whether the pre-nominal prediction effect is larger when most of the presented stories contain predictable article-noun combinations (75% predictable, 25% unpredictable) compared to when most stories contain unpredictable combinations (25% predictable, 75% unpredictable). Our results show the pre-nominal prediction effect in both contexts, with little evidence to suggest that this effect depended on the percentage of predictable combinations. Moreover, the little evidence suggesting such a dependence was primarily observed for unexpected, neuter-gender articles (‘het’), which is inconsistent with the rational adaptation hypothesis. In line with recent demonstrations (Nieuwland, 2021a,b), our results suggest that linguistic prediction is less ‘rational’ or Bayes optimal than is often suggested.

Predict or to be predicted? A transfer entropy view between adaptive green markets, structural shocks and sentiment index

This study assesses green equity markets' behavior in a sense of Lo's adaptive market hypothesis and whether this adaption could be predicted or predicts monetary and commodity structural shocks and sentiment behavior considering normal and uncertain states. Applying Domínguez-Lobato Test, SVAR decomposition and Transfer Entropy methods, the results corroborate the adaptive market hypothesis on green equity markets, and the green equity adaptive markets, structural shocks and Sentiment index are affected by tail distribution events.

Phenotypic differentiation in populations of a gladiator tree frog: environment, genetic drift and sexual selection

Abstract Phenotypic differentiation among animal populations is common, yet few studies have simultaneously examined the adaptive and neutral mechanisms behind it. Such evolutionary processes become more relevant in species with complex behaviours that undergo global and local selective pressures throughout their geographical range. Here we measured and compared morphological and acoustic variation across the distribution range of a Neotropical gladiator tree frog that shows elaborate reproduction (territoriality, complex courtship and female choice). We then incorporated molecular and landscape data to examine the roles of sexual selection, genetic drift and acoustic adaptation to the environment in call differentiation, i.e. the acoustic adaptation hypothesis (AAH). We found that calls varied more than morphology among populations, but differences in calls or morphological traits were not explained by genetic differentiation. We found no evidence for the AAH, but a significant relationship in the opposite direction regarding call frequencies suggests an indirect role of sexual selection. Differentiation on call traits that are associated with individual discrimination and/or female attraction also corroborated an important role of sexual selection. We show that multitrait and multimechanism approaches can elucidate intricate processes leading to phenotypic variation among individuals and populations. We emphasize that studies of species with complex reproductive behaviours across their range may provide insights into different selective pressures leading to phenotypic differentiation.

Community- and genome-based evidence for a shaping influence of redox potential on bacterial protein evolution.

Despite deep interest in how environments shape microbial communities, whether redox conditions influence the sequence composition of genomes is not well known. We predicted that the carbon oxidation state (ZC) of protein sequences would be positively correlated with redox potential (Eh). To test this prediction, we used taxonomic classifications for 68 publicly available 16S rRNA gene sequence data sets to estimate the abundances of archaeal and bacterial genomes in river & seawater, lake & pond, geothermal, hyperalkaline, groundwater, sediment, and soil environments. Locally, ZC of community reference proteomes (i.e., all the protein sequences in each genome, weighted by taxonomic abundances but not by protein abundances) is positively correlated with Eh corrected to pH 7 (Eh7) for the majority of data sets for bacterial communities in each type of environment, and global-scale correlations are positive for bacterial communities in all environments. In contrast, archaeal communities show approximately equal frequencies of positive and negative correlations in individual data sets, and a positive pan-environmental correlation for archaea only emerges after limiting the analysis to samples with reported oxygen concentrations. These results provide empirical evidence that geochemistry modulates genome evolution and may have distinct effects on bacteria and archaea. IMPORTANCE The identification of environmental factors that influence the elemental composition of proteins has implications for understanding microbial evolution and biogeography. Millions of years of genome evolution may provide a route for protein sequences to attain incomplete equilibrium with their chemical environment. We developed new tests of this chemical adaptation hypothesis by analyzing trends of the carbon oxidation state of community reference proteomes for microbial communities in local- and global-scale redox gradients. The results provide evidence for widespread environmental shaping of the elemental composition of protein sequences at the community level and establish a rationale for using thermodynamic models as a window into geochemical effects on microbial community assembly and evolution.

Assessment of the acoustic adaptation hypothesis in frogs using large‐scale citizen science data

AbstractAcoustic communication is vital to the survival and fitness of many vertebrates. While successful communication is reliant on acoustic signals reaching an intended receiver and maintaining content fidelity, propagating signals are attenuated by environmental factors such as habitat type. The acoustic adaptation hypothesis (AAH) predicts that the acoustic properties of signals are selected for optimal transmission in the habitats in which they propagate. To date, consistent evidence to support the theory is lacking, but studies have typically been primarily based on localized datasets with small sample sizes. Citizen science is emerging as a potential means to overcome the challenges associated with broad‐scale sampling, allowing us to assess the validity of the AAH in frogs on a continental scale. We analysed the male advertisement calls of 674 individual banjo frogs (Limnodynastes dorsalis, L. dumerilii, L. interioris and L. terraereginae) from across their range, pairing these citizen science data with remotely sensed measures of habitat complexity. While we detected considerable variation in acoustic structure within and among banjo frog species, this was not strongly correlated with habitat complexity. Thus, we found no support for the AAH. However, with our study spanning an area of over 1.7 million km2, we conducted the largest‐scale test of the AAH in frogs to date, contributing to the global understanding of acoustic signal evolution.