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Leptodactylus sertanejo Giaretta & Costa, 2007, a junior synonym of Leptodactylus jolyi Sazima & Bokermann, 1978 (Amphibia, Anura, Leptodactylidae)

The genus Leptodactylus currently comprises 84 species of predominantly Neotropical lowland frogs. The L. fuscus group is the most species-rich in the genus, including the nominal species L. jolyi and L. sertanejo. In a published comprehensive study, involving a total evidence analysis of molecular and non-molecular traits, the grouping of L. jolyi and L. sertanejo was very poorly supported, denoting indifferentiation, and indicated that both species cannot be reliably distinguished from each other morphologically. We analysed the overall morphology and color pattern of the specimens attributed to L. jolyi and L. sertanejo and verified that they are closely similar or even identical. The Comparative Anatomy Index did not present dissimilarities for any morphometric variable. Submitting the values to the Principal Component Analysis, we confirmed the morphometric similarity for all variables. To evaluate the discrepancy degree, the values obtained were submitted to the adherence test of the χ2 and we found that no significant morphometric differences did exist. The advertisement calls of 17 specimens attributed to L. jolyi and L. sertanejo are composed of a single harmonic note constituted by one to four pulses. There are no bioacoustic dissimilarities among the specimens analyzed. The multivariate canonical analysis did not discriminate differences among the specimens. Consequently, considering the poor molecular differentiation and based on the analysis of morphological and meristic characters and on advertisement calls, the synonymization of Leptodactylus sertanejo with L. jolyi is proposed.

Among the world's smallest vertebrates: a new miniaturized flea-toad (Brachycephalidae) from the Atlantic rainforest.

The genus Brachycephalus includes miniaturized toadlets with two distinct morphotypes: brightly colored species with a bufoniform phenotype and smaller, cryptic species with a leptodactyliform phenotype. The diversity of leptodactyliform species is still underappreciated, and we generally lack fundamental information about their biology. Recent sampling efforts, including DNA analyses and recordings of advertisement calls, have improved our understanding of this group. In the present study, we describe a new species of Brachycephalus, one of the smallest vertebrates known. This new species is distinguished from its congeners by a combination of morphological, bioacoustic, and genetic data. Despite being among the smallest frogs globally (the second smallest amphibian species), it exhibits skeletal traits typical of larger frogs, such as the presence of cranial bones that are lost or fused in other miniature frogs, including other Brachycephalus. Our description underscores how new discoveries within the megadiverse fauna of the Atlantic Forest-a rich biodiversity hotspot-can provide insights into phenotypic variation, including vertebrate body size. By describing this new species, we also aim to revisit the hypothesis that the type series of B. hermogenesi includes two species, potentially including individuals of the species described here.

Combining citizen science, phylogenetics, and bioacoustics to inform taxonomy and conservation of the Near Threatened Proceratophrys paviotii (Anura, Odontophrynidae).

Herein, basel on novel data gathered by citizens scientists and specialists, we contribute to the improvement of scientific knowledge and conservation of the Near Threatened Proceratophrys paviotii in order to: 1) test for the first time the phylogenetic position and a species delimitation of P. paviotii through a molecular approach; 2) describe a larger sample of its advertisement call to properly encompass the species intraspecific variation; 3) describe for the first time the P. paviotii release call; and 4) provide novel insights on the species conservation status. Our 16S tree confidently grouped P. paviotii with P. cururu, P. renalis, and P. laticeps. The average sequence divergence between P. paviotii and its congeners ranged from 2.2% (P. laticeps) to 9.1% (P. redacta). Advertisement calls consisted of a single note with duration of 0.26-0.58 s, 17-41 pulses emitted at rate of 54.19-77.49 pulses/s and peak frequency of 775.19-947.46 Hz. Release calls consisted of a single note with duration of 0.04-0.43 s, 2-13 pulses emitted at rate of 21.17-81.58 pulses/s and peak frequency of 689.1-1,722.6 Hz. Additionally, our study strongly supports the notion that Citizen Science approaches can yield invaluable information concerning species' geographic distribution and conservation.

Communicator whistles: A Trek through the taxonomy of the Boophis marojezensis complex reveals seven new, morphologically cryptic treefrogs from Madagascar (Amphibia: Anura: Mantellidae)

Abstract The Malagasy stream-breeding treefrog species Boophis marojezensis contains bioacoustically and genetically highly divergent populations. Some of these populations have been defined as candidate species and emit somewhat bizarre advertisement calls consisting of multiple whistle-notes. We here enable a long-overdue taxonomic revision of this species complex by applying a museomics approach to sequence DNA from the holotype of B. marojezensis. Based on an integrative approach that combines divergence levels in mitochondrial DNA and in three nuclear-encoded genes, morphological data, and bioacoustic comparisons, we conclude that eight different species exist in this complex, seven of which are formally described herein as new. Although morphological differences between species are small and mainly separate small-sized from larger-sized species, conclusive evidence for the new species comes from their sympatric and sometimes syntopic occurrence without haplotype sharing in three nuclear genes and under maintenance of bioacoustic differences. Uncorrected genetic divergences in the mitochondrial 16S rRNA gene are >3% in almost all cases, and in some cases up to 8%. In reference to the otherworldly sounds by which these frogs fill Malagasy rainforests, some of them reminiscent of sounds of technical equipment in the fictional “Star Trek” universe, we here name and describe the seven new species in honor of fictional captains of starships, namely B. kirkisp. nov., B. picardisp. nov., B. siskoisp. nov., B. janewayaesp. nov., B. archerisp. nov., B. pikeisp. nov., and B. burnhamaesp. nov. The majority of these species occur in northern Madagascar, where up to three species can occur in immediate geographical proximity, e.g., B. marojezensis, B. burnhamaesp. nov. and B. pikeisp. nov. at different elevations in the Marojejy Massif. South of 16°S latitude, only B. janewayaesp. nov., B. picardisp. nov., and B. kirkisp. nov. are found, with the latter extending southwards to Ranomafana National Park. Our study confirms the existence of numerous morphologically cryptic and microendemic species among Madagascar’s amphibians, some of which are known only from unprotected sites and require adequate conservation management.

Diversity and distribution of reed frogs (Hyperolius spp.) on Bioko Island, Equatorial Guinea

Reed frogs (Hyperolius spp.) are the most species-rich genus in the family Hyperoliidae, a group of frogs endemic to sub-Saharan Africa and the Gulf of Guinea islands. Three species are endemic to oceanic islands in the archipelago, but the diversity and distribution of reed frogs on Bioko – a land-bridge island in the archipelago – remains unclear. Two species, H. tuberculatus and H. ocellatus ocellatus, were formally documented on Bioko in the colonial era, however, two additional reed frog species have been detected in recent surveys. In addition, observations of heterospecific amplexus suggest one of the unidentified species and H. o. ocellatus may be hybridising on the island. In this study, we examined mitochondrial DNA (mtDNA), nuclear DNA (nuDNA), morphological and acoustic data to confirm the tentative identifications of the reed frogs and determine if there is any evidence of hybridisation. Our data confirm that the two unidentified species are H. endjami and H. fusciventris, and that Bioko H. endjami have unique genetic diversity not shared with the mainland population. Additionally, our mitochondrial (16S) and nuclear DNA (CMYC) haplotype networks suggest that H. o. ocellatus and H. endjami are not hybridising on Bioko. Finally, we report colour pattern variation in H. endjami and H. o. ocellatus that is unique from populations on the continent, and describe male advertisement calls of Bioko H. endjami and H. o. ocellatus. Our study provides a first look at the diversity and distribution of reed frogs on Bioko Island and sets the stage for future studies of the ecology, evolution, and conservation of this island community. KEYWORDS: hybridisation, polymorphism, mitochondrial and nuclear DNA, morphology, land-bridge island

Anuran occupancy varies with stream characteristics and flow across Arizona wilderness areas

Abstract Riparian ecosystems comprise less than 2% of the landscape in the arid western United States, yet they provide habitat and resources to over half of arid‐land wildlife species, including a broad diversity of anurans (frogs and toads). Despite this, relatively few studies describe riparian herpetofaunal communities in the Southwest, and remote wilderness areas are particularly undersurveyed. We employed passive acoustic monitoring to capture anuran advertisement calls in wilderness area tributaries of the Verde River, Arizona, USA. In the spring and summer of 2021 and 2022, 13–29 autonomous recording units (ARUs) were deployed along perennial, intermittent and ephemeral tributary stream reaches. We characterized sites based on the per cent of pool, riffle, run and side channel habitat within 100 m of each ARU and quantified substrate, wetted channel width and canopy cover. To relate anuran occupancy to environmental and hydrological variables, we evaluated acoustic detection data using single‐species, single‐season occupancy models. Four species were detected in this study: canyon treefrog (Hyla arenicolor), red‐spotted toad (Anaxyrus punctatus), Woodhouse's toad (Anaxyrus woodhousii) and non‐native American bullfrog (Lithobates catesbeianus), with canyon treefrog being the most ubiquitous species observed. Vocal activity of canyon treefrog was higher at perennial and intermittent sites compared to ephemeral sites, and the presence of pools was most strongly associated with canyon treefrog occupancy. Persistent, slow‐moving water best predicted the presence of breeding canyon treefrogs. Notably, this study did not detect several species with historical records in the middle Verde River catchment, including Arizona toad (Anaxyrus microscaphus) and northern leopard frog (Lithobates pipiens). Given climate change‐related flow declines and intensifying demands for water in arid lands globally, maintaining stream flows that provide consistent and suitable hydroregimes for anuran breeding and larval development is of increasing importance. Determining habitat use and flow regimes necessary to support anuran populations can aid in prioritization of conservation actions related to water management and predict how changes in water availability may impact stream‐breeding anurans.

Assessing the impact of engine and non-engine urban noises on the calls of urban frogs: a natural experiment

Urban noise can potentially disturb the acoustic signals of animals inhabiting urban areas. Although a wide variety of noises from different sources is common in cities, the impact of non-engine noise on animal calls is less studied. In a natural experiment, we evaluated the effect of different urban noises on the advertisement calls of urban frogs (Eleutherodactylus nitidus) in the metropolitan area of Puebla, Mexico. We recorded and analyzed 672 advertisement calls from 28 male frogs and the corresponding environmental noises from three distinct localities. Our analysis focused on four acoustic properties of the calls: inter-call interval, call duration, dominant frequency, and call amplitude. To standardize the amplitude measurements of sound pressure levels produced by noise and frog calls, we employed a practical approach using a reference signal for calibration. We treated the longitudinal data of different noises occurring before, during, and after advertisement calls as repeated measures within the urban locations. During our samplings, frogs called amidst spontaneous urban noises, including dog barking, fireworks, and vehicle engine sounds. Our results indicate that vehicle engine sounds and dog barking do not cause significant distortions in the calls of these urban frogs. However, we observed slight variations in the dominant frequency of calls, decreasing by 11 Hz, during and after fireworks. Given the observed plasticity of E. nitidus in response to noise, urban noises may not pose a severe problem for this urban frog.

What do frog calls tell us about males? The advertisement call of Physalaemus albifrons (Amphibia: Leptodactylidae) in the Brazilian semiarid region does not reflect either gonadal investment or energy storage

ABSTRACT Anuran advertisement calls can provide accurate information on the reproductive quality of the male callers, thus providing females with indicators for the selection of mates. Body size is generally correlated with the dominant frequency of male advertisement calls. However, it is unclear whether and to what extent call parameters are associated with gonadal investment and the energy reserves of the males. Given that in tropical seasonally dry environments the wet season is very short, gathering information about gonadal investment and energy reserves of mates should be particularly important. In the present study, we evaluated the relationship between acoustic performance, gonadal condition, and fat storage in the Neotropical frog Physalaemus albifrons from the Brazilian semiarid region, testing the hypothesis that the advertisement call (repetition rate, call duration, and fundamental and dominant frequencies) would be a good predictor of male quality in terms of gonadal investment (testicle length) and energy reserves (mass of fat bodies). Contrary to our predictions, neither testicle length nor the mass of fat bodies was related to any of the acoustic parameters of the advertisement calls of P. albifrons. These results indicate that the advertisement call of P. albifrons does not provide reliable information on gonadal investment or energy storage of males. Possibly, in habitats with little and unpredictable rainfall, males of P. albifrons should present small variation in gonadal and fat storage conditions during its short reproductive window. Our findings contribute to the understanding of anuran reproductive strategies in seasonally dry environments.

Prescribed fire and natural habitat characteristics affect crawfish frog (Rana areolata) advertisement call transmission

ABSTRACT For acoustically signalling animals, the rate of signal degradation is critical for successful communication. Degradation is heavily influenced by habitat characteristics, with sound degrading more rapidly in the presence of environmental obstacles (e.g. vegetation). Land management strategies such as prescribed burns eliminate obstacles and should therefore lead to more efficient sound transmission. Crawfish frogs (Rana areolata) produce long-distance advertisement calls for breeding. Habitats surrounding crawfish frog breeding ponds vary in vegetative density, and prairies surrounding breeding habitat often undergo controlled burns prior to the breeding season. We hypothesised that R. areolata advertisement calls would transmit more efficiently in post-burned prairies compared to other more vegetated habitats. To test this hypothesis, we conducted a sound transmission playback experiment, broadcasting crawfish frog calls in three habitats: forest, prairie, and post-burned prairie. We compared sound degradation measures between habitat types and across distances. We found that crawfish frog calls experienced up to 6.8 dB less excess attenuation in post-burned habitats relative to other habitat types, and that in general, prairie habitats had better sound transmission than forest. These results indicate that land management and habitat structure have consequences for acoustic communication, and may also influence the findings of frog call detection surveys.

Novel and classical methods similarly describe variation in territory size among males in Neotropical poison frogs with contrasting reproductive and behavioral strategies

AbstractTerritoriality is a form of social dominance concerning the use of space that ensures the territory owner primary access to critical resources. The territory is defended with visual displays, advertisement calls, physical attacks, or chemical signals. The territory is frequently estimated by mapping locations where an animal is observed engaging in territorial behavior or by tracking. However, these approaches may over- or underestimate the areas defended. Thus, the use of approaches explicitly determining defended areas is critical to properly characterize the territory. Intrusion experiments can elicit a response in territory holders, allowing one to characterize their aggressive responses; however, the aggressive response depends on the species. We describe an approach to experimentally estimate the territory size using playback experiments in a species that exhibits a stereotypical phonotactic response: the nurse frog, Allobates aff. trilineatus and develop a new behavioral index that allows assessing territory size in response to playbacks for a species with non-stereotyped phonotactic response: the endangered Lehmann’s poison frog, Oophaga lehmanni. We conducted 772 playback experiments on 18 males of A. aff. trilineatus, and 222 on nine males of O. lehmanni. We analyzed the results of playback experiments with three different area estimators regularly used to estimate space use and evaluated whether these estimates are correlated. The shape and size of territories varied among individuals and estimators in both species. Although we found that the absolute size of the territory depends on the method used, estimates were strongly correlated, meaning that different estimators similarly describe variation in territory size among males. Choosing an analysis method may not be particularly important for studying the characteristics of territoriality over space and time but using a systematic and standardized experimental approach that also incorporates the particularities of the aggressive response of each species is essential to understand the evolution of space use by poison frogs and other territorial species.

Daily variation and repeatability of advertisement calls in an austral temperate forest frog under controlled conditions

AbstractEstimating repeatability allows a first approximation that may indicate a potential response to selection of sexual traits. Acoustic sexual signals comprise spectral and temporal variables, where the former generally have lower intra‐individual variation and higher repeatability values. Studies of repeatability in anurans have been conducted mainly in natural conditions, but the stability of laboratory settings allows extended recording intervals, favoring measurement accuracy. We conducted a study of variation and repeatability of the calls of males of Batrachyla taeniata, a frog from the South American temperate forest to evaluate under homogeneous environmental and social conditions: (i) the extent of variation in acoustic properties of calls within and among days, (ii) the extent of temporal variation in the repeatability of call properties, and (iii) differences in repeatability among call variables. Variation of acoustic properties differed within and across days of recording, call rate generally increased within and throughout days, suggesting sensitization processes. Call duration decreased during these time spans, yielding constant calling effort. In contrast, the dominant frequency decreased within days but increased across days. Overall repeatability differs significantly among variables: dominant frequency, call rate, and call duration having the highest, intermediate, and lowest values, respectively. The high repeatability of call rate relative to call duration contrasts with an opposing general tendency in previous studies in anurans. The repeatability of the three variables analyzed increases within days, and the repeatability of call rate also increases throughout days, highlighting the relevance of this variable for individual identity over different time ranges.

Time and place affect the acoustic structure of frog advertisement calls

Abstract Acoustic communication signals are important for species recognition and mate attraction across numerous taxa. For instance, most of the thousands of species of frogs have a species-specific advertisement call that females use to localize and discriminate among potential mates. Thus, the acoustic structure of the advertisement call is critical for reproductive success. The acoustic structure of calls will generally diverge over evolutionary time and can be influenced by the calls of sympatric species. While many studies have shown the influence of geography on contemporary call variation in populations of frogs, no study has compared the acoustic structure of frog calls across many species to ask whether we can detect an influence of divergence time and overall geographic overlap on the differences in acoustic structure of species-typical calls that we observe now. To this end, we compared acoustic features of the calls of 225 species of frogs within 4 families. Furthermore, we used a behavioral assay from 1 species of frog to determine which acoustic features to prioritize in our large-scale analyses. We found evidence that both phylogeny (time) and geography (place) relate to advertisement call acoustics albeit with large variation in these relationships across the 4 families in the analysis. Overall, these results suggest that, despite the many ecological and evolutionary forces that influence call structure, the broad forces of time and place can shape aspects of advertisement call acoustics.

Larval morphology, vocalisations, and phylogenetic position of Crossodactylus dantei (Anura: Hylodidae): new insights into a little-known anuran species

Aspects of the biology and natural history of the endemic anuran Crossodactylus dantei remain unknown even almost 30 years since its description. In this study, we describe its larval stage, along with the advertisement and territorial calls, and assess its phylogenetic positioning based on a fragment of the 16S rRNA mitochondrial gene. The larval stage of C. dantei follows the morphological pattern of Hylodidae, corroborating the relatively uniform larval morphology of the family. However, it is still possible to observe characters that distinguish C. dantei from other species in the genus, such as the elliptical body in dorsal view, nostrils located closer to the snout than to the eyes, an elongated pre-nasal arena, and the absence of taenia tecti medialis and taenia tecti transversalis in the chondrocranium. Its advertisement call is characterised by a sequence of about 23 pulsed notes, with ascending amplitude modulation, and has a mean duration of 2.5 seconds, with a dominant frequency of 3356 Hz. The territorial call has a mean duration of 23 seconds, a dominant frequency of 3160 Hz, and two distinct types of notes. Phylogenetic analysis indicated the existence of two main lineages in the genus. Crossodactylus dantei was recovered with high statistical support as a sister species to the clade composed of C. gaudichaudii and C. timbuhy. Furthermore, the group formed by these three species was recovered as the sister lineage of C. trachystomus. In summary, the information presented here represents a significant advance in the knowledge of this enigmatic and rare species of the northern Atlantic Forest, providing baseline data for future ecological and evolutionary studies of this unique frog. Keywords: tadpole, oral anatomy, chondrocranium, calls, phylogeny, Atlantic Forest

Potential effects of traffic noise on anuran call characteristics in Louisiana, USA during winter.

Urban environments expose wildlife to levels of anthropogenic noise they would not experience in rural areas (e.g., traffic noise), and research suggests that many species adjust their acoustic signals for optimal transmission in urban soundscapes. However, our understanding of anuran (order Anura) responses to noise pollution in urban environments of the southeastern United States is limited, particularly for species that can breed during winter. Our goal was to examine how vocal anuran advertisement call characteristics during winter varied with increasing distance from roadways in bottomland hardwoods of Louisiana, USA. We deployed acoustic recording units at two sites (i.e., rural and urban) perpendicular to Interstate 10 at 200-, 400-, and 600-m intervals (i.e., close, middle, and far) from November 2019 to January 2020. We detected Cajun Chorus Frogs (Pseudacris fouquettei) and Cricket Frogs (Acris spp.) at our rural site, and only detected Cricket Frogs at our urban site. At the rural site, Cajun Chorus Frogs produced longer duration notes at the far location compared to the middle location. At the urban site, Cricket Frogs produced higher dominant frequency calls at the close location compared to the far and middle locations and longer duration notes at the far location compared to the close location. We were unable to account for additional factors in our models (e.g., temperature, noise levels), but our results generally align with previous research. Our study provides baseline data for future research to examine the potential effects of traffic noise on winter advertisement calls in locations with similar environmental conditions and species.

Visual cues do not function in a multimodal signalling context for mate attraction in eastern gray treefrogs

Abstract Anurans use different sensory modalities to communicate and interact socially, including acoustic, chemical, tactile, and visual signals. In a multimodal context, these sensory modes can transmit different information to the receiver or even reinforce the same message. In this study, we hypothesized that body colour traits and vocal sac movements of male eastern gray treefrogs [Dryophytes versicolor (= Hyla versicolor)] serve as secondary visual cues that increase their attractiveness while calling to attract mates. We tested this hypothesis using playback trials combining synthetic advertisement calls with a variety of visual cues, including differently coloured resin frog models, simulated vocal sacs, and live frogs. None of the visual stimuli tested impacted female choice, and there was no difference in response rate, response time, choice angle, or distance covered in the arena between multimodal and unimodal stimuli. However, females showed a strong preference for longer calls even if the less attractive calls were paired with a visual stimulus. The study provides comprehensive insights into the role of visual stimuli in the mate attraction of eastern gray treefrogs and suggests that call traits play a dominant role in the male-selection process of this species, contrary to what was observed for visual stimuli.

Meal or mate: Exploring the evidence of sexual cannibalism among amphibians.

Active forms of cannibalism that involve predation of live conspecifics occur widely among amphibians, most notably by tadpoles that feed on each other and adults that feed on juveniles. In contrast, cannibalism among amphibian adults (adult-adult cannibalism) is less often reported and there have been no investigations on the occurrence of sexual cannibalism in this group to date. In this study, we present an observation of potential sexual cannibalism involving an adult female green and golden bell frog, Litoria aurea, preying on a conspecific adult male during the species' breeding season. By comparing our observation to the available literature, we show that adult-adult cannibalism among amphibians is rare but tends to be committed by females against their male counterparts. We thus suggest that the occurrence of sexual cannibalism should be extended to include this group, where sexual size dimorphism occurs widely among adults that congregate spatially during breeding periods, both predictors of intra-specific predation. We hypothesise that amphibian females may be able to exploit male advertisement calls to differentiate suitable partners from potential prey and that male individuals are vulnerable to sexual cannibalism as they must risk attracting and physically exposing themselves to females in order to reproduce. Our findings reveal the complex dynamics that exist within adult amphibian populations, suggesting that females may have a choice when deciding how to interact with and utilise their male counterparts. As our findings are preliminary, based on a small sample size of records, including several from captive individuals, we encourage authors to publish their observations of cannibalism in the field, including unsuccessful attempts, to confirm the presence of sexual cannibalism in this group.

Similar looking sisters: A new sibling species in the Pristimantis danae group from the southwestern Amazon basin (Anura, Strabomantidae)

We describe a new frog species that is the sibling of Pristimantis reichlei. These two sister species inhabit the Amazonian lowlands and adjacent foothills of the Andes, from central Bolivia to central Peru. Pristimantis reichlei occurs from central Bolivia to southern Peru (Alto Purús National Park), while the new species occurs from northern Bolivia (Departamento Pando) to Panguana in central Peru (Departamento Huánuco), at elevations between 220 and 470 m a.s.l. In spite of their morphological crypsis, these siblings occur in syntopy without evidence of interbreeding (in the Alto Purús area) and are recovered as reciprocally monophyletic. Their uncorrected pairwise genetic distances in the 16S rRNA gene range from 9.5–13.5%, and their advertisement calls differ in both qualitative and quantitative traits. Moreover, our study found uncorrected pairwise distances within the new species of up to 5.0% and up to 9.3% within P. reichlei. We therefore cannot rule out the possible existence of hybrids or additional species-level lineages hidden in this complex. Furthermore, we found another potential pair of sibling species composed of P. danae and an unnamed lineage, with divergences of 9.4% in the 16S gene, whose in-depth analysis and taxonomic treatment are pending future revision. With the new nominal species, the Pristimantis danae species group now includes 20 species, distributed across the upper Amazon basin and in the eastern Andes, from western Brazil to Bolivia and Peru. Our study, together with an increasing number of other studies, indicates that sibling species are far from being rare among Amazonian amphibians and that species resolution remains low even for groups that have received considerable attention in recent years.

Substrate specialisation drives an unexpectedly diverse radiation in barking geckos (Ptenopus: Gekkonidae)

Barking geckos (genus Ptenopus) are terrestrial, burrowing lizards endemic to southern Africa, currently with three recognised species. Two species are range-restricted (P. kochi and P. carpi) and display clear differences in substrate preference (soft sand vs. hard gravel). The third and most widespread species, P. garrulus, occurs on a variety of substrates of differing hardness, across potential geographic barriers, and over a steep climatic gradient. Variations in morphology and advertisement calls indicates that P. garrulus may be a species complex. Two subspecies of P. garrulus are currently recognised: P. g. maculatus and P. g. garrulus. To investigate species boundaries, we produced the first comprehensive phylogeny for the genus. We used a novel application of multiple regression on matrices models to assess multiple environmental drivers of diversification, as contrasted to isolation by distance. We show that P. kochi, P. carpi, and P. g. garrulus are valid species, but that P. g. maculatus is a paraphyletic complex of five previously unrecognised taxa. Specialisation onto different substrates was likely the main driver of divergence, with parapatric occurrence of two to four clades occurring at each of the three substrate transition zones identified a priori. The region encompasses diverse bioclimatic regions and potential geographic barriers, and these likely played a role in some divergence events.

Perceptually salient differences in a species recognition cue do not promote auditory streaming in eastern grey treefrogs (Hyla versicolor).

Auditory streaming underlies a receiver's ability to organize complex mixtures of auditory input into distinct perceptual "streams" that represent different sound sources in the environment. During auditory streaming, sounds produced by the same source are integrated through time into a single, coherent auditory stream that is perceptually segregated from other concurrent sounds. Based on human psychoacoustic studies, one hypothesis regarding auditory streaming is that any sufficiently salient perceptual difference may lead to stream segregation. Here, we used the eastern grey treefrog, Hyla versicolor, to test this hypothesis in the context of vocal communication in a non-human animal. In this system, females choose their mate based on perceiving species-specific features of a male's pulsatile advertisement calls in social environments (choruses) characterized by mixtures of overlapping vocalizations. We employed an experimental paradigm from human psychoacoustics to design interleaved pulsatile sequences (ABAB…) that mimicked key features of the species' advertisement call, and in which alternating pulses differed in pulse rise time, which is a robust species recognition cue in eastern grey treefrogs. Using phonotaxis assays, we found no evidence that perceptually salient differences in pulse rise time promoted the segregation of interleaved pulse sequences into distinct auditory streams. These results do not support the hypothesis that any perceptually salient acoustic difference can be exploited as a cue for stream segregation in all species. We discuss these findings in the context of cues used for species recognition and auditory streaming.

Unravelling male advertisement call variability in the brown tree frog (Litoria ewingii) complex by using citizen science

In the face of global biodiversity declines, conservation measures are urgently needed. However, our lack of knowledge on species’ diversity, distributions and population trends presents a major obstacle, particularly for morphologically cryptic species. Field surveys to gather this information present a logistical challenge, but the rapid rise of citizen science presents a new opportunity, generating huge volumes of data rapidly across a species’ range. We use data from a national citizen-science project to document the distribution and advertisement call variability in a group of five morphologically conserved treefrogs. Using 542 male advertisement calls across the entire range of five species, we found considerable levels of acoustic variation both among and within species. Note shape, notes per call and positions of the longest and shortest notes were most useful to delineate species. Our research will assist in species delineation and identification in the field and form the basis for a more accurate understanding of species diversity and distributions in the brown tree frog complex. We also demonstrated the utility of citizen science in documenting species distributions and diversity.