Mating Calls Research Articles

Not so cryptic-differences between mating calls of Hyla arborea and Hyla orientalis from Bulgaria.

Anurans are among the most vocally active vertebrate animals and emit calls with different functions. In order to attract a mate, during the breeding season male frogs produce mating calls which have species-specific structure and parameters, and have been successfully used to resolve issues in taxonomy and phylogenetic relations. This is particularly useful when closely related taxa are concerned, as many species are morphologically almost identical, but still their status is well-supported by molecular and genetic data, suggesting the existence of mechanisms for reproductive isolation. Such is the case for treefrogs from the Hyla arborea group, which are now recognized as several distinct species. The present study aims to establish differences in call parameters between the European tree frog, Hyla arborea, and the Eastern tree frog, Hyla orientalis, which both occur on the territory of Bulgaria. Using autonomous audio loggers, calls from six sites (three in the range of H. arborea and three in the range of H. orientalis) were recorded between 7 p.m. and 12 a.m. during the breeding season in 2020-2023. The following parameters in a total of 390 mating calls were analyzed: call count, pulse count, call series duration, call period, peak (dominant) frequency, entropy. Results indicated that sites formed two distinct groups, which corresponded to the known distribution ranges of H. arborea and H. orientalis. The first two components of the PCA explained 71% of the total variance, with variables call count, call series duration, peak frequency and entropy being most important for differentiation between the sites. This study presents the first attempt to differentiate between the calls of these two sister taxa, which both fall within the "short-call treefrogs" group, and results are discussed in terms of known data for mating calls in Hyla sp., as well as limitations and future perspectives.

Inter-individual variability in developmental traits in tadpoles of the Baja California chorus frog (Pseudacris hypochondriaca) in response to temperature

Phenotypic plasticity is the intraspecific expression of different phenotypes in response to environmental conditions. Inter-individual variability refers to the range of phenotypes produced between conspecifics within a population, and such variability is ubiquitously observed among animals. Investigating inter-individual variability can help develop a more comprehensive understanding of how phenotypes respond to environmental change. The Baja California chorus frog ( Pseudacris hypochondriaca) is found in a variety of ecosystems that differ in temperature and elevation throughout its latitudinal range (∼1400 km) from Santa Barbara County, California to Baja California, Mexico. The chorus frog experiences a variable thermal environment across its life history and males initiate mating calls at a wide range of water temperatures, between 4 and 20°C. Embryos develop successfully between 8 and 29°C, and tadpoles between 0 and 33°C. We have previously observed inter-individual variability in developmental traits, such as development rate and metabolic rate, and therefore aimed to investigate this variability within and between temperatures more closely. Chorus frog eggs were collected from a wetland on the CSUSM campus the day after being laid, and incubated at 15°C or 22°C. Once tadpoles reached the target stage (Gosner Stage 33; hind limb toe differentiation), oxygen consumption rate (Vȯ2) was measured using intermittent respirometry, and body length, wet mass and dry gut-free masses were measured. We also investigated the effect of temperature on swimming speed and time to exhaustion. Average time to stage, wet mass, dry gut-free mass and body length all decreased at 22°C, while mass-specific Vȯ2 increased. We observed decreased variability at 22°C compared to 15°C in time to reach stage (days from first to last tadpole to reach stage: 30.2 ± 2.7 days at 15°C, 15.4 ± 1.1 at 22°C), wet mass (wet mass range: 148.8 ± 14.2 mg at 15°C, 105.1 ± 11.3 mg at 22°C), and dry gut-free mass (dry gut-free mass range: 14.2 ± 1.2 mg at 15°C, 7.3 ± 0.7 mg at 22°C). Variability in body length did not differ between temperatures (total length range: 7.7 ± 0.4 mm at 15°C, 6.4 ± 0.5 mm at 22°C). In contrast to other traits, variability in mass-specific Vȯ2 increased at 22°C compared to 15°C (mass-specific Vȯ2 range: 0.61 ± 0.07 μl h−1 mg−1 at 15°C, 1.63 ± 0.21 μl h−1 mg−1 at 22°C). Overall, there is a correlation between the average effect of temperature and the inter-individual variability of phenotypic traits, with higher temperature resulting in less inter-individual variability in development rate and morphological characteristics, which are faster and smaller at higher temperature, while variability in mass-specific Vȯ2 increased with temperature, reflecting the increase in average Vȯ2 that occurs at higher temperature. CS supported by a Beckman Scholarship. CAM supported by a CSUSM Research, Scholarship and Creative Activities Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Condition dependence in the sexual communication system of the túngara frog

Sexual selection can result in the evolution of extreme armaments and ornaments, and the development and maintenance of these traits can come at a considerable cost. These costs have been implicated in enforcing an upper limit on trait divergence and promoting condition-dependent traits, such that only individuals in sufficiently high condition can effectively wield these armaments and advertise these ornaments. Numerous studies demonstrate the condition-dependence of sexually selected traits, especially those used by males to advertise to females. In this study, we investigated condition-dependent mating calls in the túngara frog Physalaemus (= Engystomops) pustulosus. We manipulated male condition in the laboratory over a nine-day period by restricting food availability. We then documented: the relationship between male condition (the relative change in body mass from night 1 to night 9) and acoustic parameters of his mating call; how male condition influenced the male’s responses to call playbacks; and finally, how male condition influenced the attractiveness of the male’s calls to females. Males who were not fed during this period showed significant changes in call frequency, duration, and amplitude. In response to playbacks, unfed males called less, and made fewer complex calls. Finally, in phonotaxis experiments, females were more attracted to the calls of unfed males on night 1 to the calls of the same males on night 9. Fed males, on the other hand, showed no significant differences between nights 1 and 9 in call parameters, calling effort, and call attractiveness. This study shows the pervasive effects of condition on three aspects of sexual communication: signal parameters, behavioral response to vocal competition, and mating call attractiveness.

Development and optimization of a novel environmental DNA‐based method for moor frog (Rana arvalis) monitoring and comparison with a commercial detection kit

AbstractMoor frogs (Rana arvalis) are protected by the European Union's Habitats Directive, often making them a target for environmental impact assessments. However, moor frog detection with the traditional method using their mating calls is difficult, time‐consuming, and limited to the short mating season. Environmental DNA (eDNA)‐based methods could be beneficial in moor frog detection since moor frogs are shy and co‐occurring common frogs (R. temporaria) are morphologically similar. Additionally, eDNA‐based methods could even extend the detection period of moor frogs. We tested two different DNA isolation methods and two different eDNA detection methods, Sanger sequencing and quantitative PCR (qPCR), and compared the results to the traditional mating call survey method. In addition, we tested whether linear polyacrylamide treatment would improve eDNA detection. We sampled 27 sites in Finland, of which moor frogs were detected in 17 sites by traditional acoustic survey method, in 20 sites with Sanger sequencing‐based eDNA method, and in 21 sites with qPCR‐based eDNA method. We sampled water bodies during and 3–4 weeks after the end of the mating season. Our results show that both tested eDNA methods (Sanger sequencing and qPCR) can be used to detect moor frogs and extend the moor frog detection period by at least 3–4 weeks, but qPCR slightly outperforms Sanger sequencing. Linear polyacrylamide treatment did not improve the results. Detection probabilities were similar or higher with the eDNA‐based methods than with the traditional survey method, as moor frogs were also detected in water bodies in which mating calls were not heard. Based on our results, eDNA‐based detection methods can be highly beneficial in monitoring the presence of moor frogs and can be used to complement traditional surveys.

Phenotypic plasticity of male calls in two populations of the katydid Neoconocephalus triops (Insecta: Tettigoniidae)

The ability to respond to environmental changes plays a crucial role for coping with environmental stressors related to climate change. Substantial changes in environmental conditions can overcome developmental homeostasis, exposing cryptic genetic variation. The katydid Neoconocephalus triops is a tropical species that extended its range to the more seasonal environment of North America where it has two reproductive generations per year. The harsher winter conditions required adults to diapause which resulted in substantially different mating calls of the diapausing winter animals compared to the non-overwintering summer animals in northern Florida. The summer call corresponds to that of tropical populations, whereas the winter call represents the alternative call phenotype. We quantified call plasticity in a tropical (Puerto Rico) and a temperate population of N. triops (Florida) that differ in experiencing winter conditions in their geographic regions. We hypothesized that the plastic call traits, i.e., double-pulse rate and call structure, are regulated independently. Further, we hypothesized that phenotypic plasticity of double-pulse rate results in quantitative changes, whereas that of call structure in qualitative changes. We varied the photoperiod and duration of diapause during male juvenile and adult development during rearing and analyzed the double-pulse rate and call structure of the animals. Double-pulse rate changed in a quantitative fashion in both populations and significant changes appeared at different developmental points, i.e., the double-pulse rate slowed down during juvenile development in Florida, whereas during adult diapause in Puerto Rico. In the Florida population, both the number of males producing and the proportion of total call time covered by the alternative call structure (= continuous calls) increased with duration spent in diapause. In the Puerto Rico population, expression of the alternative call structure was extremely rare. Our results suggest that the expression of both pulse rate and call structure was quantitative and not categorical. Our systematic variation of environmental variables demonstrated a wide range of phenotypic variation that can be induced during development. Our study highlights the evolutionary potential of hidden genetic variation and phenotypic plasticity when confronted with rapidly changing environments and their potential role in providing variation necessary for communication systems to evolve.

Mate calling alters expression of neuropeptide, cocaine- and amphetamine- regulated transcript (CART) in the brain of male frog Microhyla nilphamariensis

Croaking is a unique component of reproductive behaviour in amphibians which plays a key role in intraspecies communication and mate evaluation. While gonadal hormones are known to induce croaking, central regulation of sound production is less studied. Croaking is a dramatic, transient activity that sets apart an animal from non-croaking individuals. Herein, we aim at examining the profile of the neuropeptide cocaine- and amphetamine-regulated transcript (CART) in actively croaking and non-croaking frog Microhyla nilphamariensis. In anurans, this peptide is widely expressed in the areas inclusive of acoustical nuclei as well as areas relevant to reproduction. CART immunoreactivity was far more in the preoptic area (POA), anteroventral tegmentum (AV), ventral hypothalamus (vHy), pineal (P) and pituitary gland of croaking frog compared to non-croaking animals. On similar lines, tissue fragments collected from the mid region of the brain inclusive of POA, vHy, AV, pineal and pituitary gland of croaking frog showed upregulation of CART mRNA. However, CART immunoreactivity in the neuronal perikarya of raphe (Ra) was completely abolished during croaking activity. The data suggest that CART signaling in the brain may be an important player in mediating croaking behaviour in the frog.

Studying mate choice using inertial measurement units: a validation study with treefrogs

Investigations of mate choice continue to address fundamental questions about the mechanisms and evolution of animal behaviour. A common behavioural assay used to study acoustically guided mate choice with playback experiments is phonotaxis, a typically robust response in which a chooser approaches acoustic signals, such as courtship songs or mating calls. Robust empirical studies of phonotaxis often require substantial laboratory facilities, such as a dedicated and sound-treated room or enclosure, in which the acoustic environment is controlled and in which animals are freely able to move about. The financial and space resources required to outfit a research laboratory to investigate phonotaxis may be sufficiently prohibitive such that some researchers are excluded from undertaking bioacoustic behavioural research. Here, we validate a new device designed to measure animal movements related to phonotaxis using an inertial measurement unit (IMU). The device is small and portable; it can be constructed for less than $300 USD (£ 238 GBP); and the build instructions and code for operation are freely available. In a series of four experiments with treefrogs, we demonstrate using the device that an IMU-based approach to measuring animal movement can replicate a broad range of findings from traditional phonotaxis experiments on species recognition and sexual selection. We conclude by discussing several possible uses for IMU-based measurements of phonotaxis.

Insect mating calls drowned out by rowdy humans

Insect mating calls drowned out by rowdy humans

Seasonal Changes in Hematological Parameters in House Sparrows of Subtropical Pakistan.

House sparrow is a globally adaptive bird. The way this creature adapted to all areas of the world, having different selection pressures, is interesting to understand. The present study is focused on seasonal changes, having different selection pressures and how it is adapted to these changes and whether hematological flexibility plays a role in this success. House sparrow's adaptations in the same area, during different seasons, have been studied in a sub-tropical area, Potohar, Pakistan. We used hematological parameter analysis for this purpose. Blood samples were collected from Sparrows in winter, spring, and summer and analyzed for some hematological parameters. White blood cells (WBCs) were higher in spring and summer which may relate to mating promiscuity. Sparrows were more stressed in summer. The Red blood cells (RBCs) and hematocrit (Hct) were greater in summer. Mean corpuscular volume (MCV) is lower in summer. This may have an adaptation to cope with high stress in summer as small-size RBCs increase gaseous exchange. Platelets were not affected by season or gender. Mean corpuscular volume and Mean corpuscular hemoglobin (MCH) are positively correlated with each other. Red blood cells, hemoglobin (Hb) and MCV were higher in males during the spring season perhaps as an adaptation to energetic activities during spring like mating calls and search for nesting sites. White blood cells remained the same in both genders in summer and winter, and effected in spring may be related to the mating system. Behavioral state is linked with physiological states that shows tradeoff and life history traits. This study is a small effort to know this incredible species. We can work further in different parts of the world to explore different aspects of it.

Climate Change Alters Sexual Signaling in a Desert-Adapted Frog.

AbstractClimate change is altering species' habitats, phenology, and behavior. Although sexual behaviors impact population persistence and fitness, climate change's effects on sexual signals are understudied. Climate change can directly alter temperature-dependent sexual signals, cause changes in body size or condition that affect signal production, or alter the selective landscape of sexual signals. We tested whether temperature-dependent mating calls of Mexican spadefoot toads (Spea multiplicata) had changed in concert with climate in the southwestern United States across 22 years. We document increasing air temperatures, decreasing rainfall, and changing seasonal patterns of temperature and rainfall in the spadefoots' habitat. Despite increasing air temperatures, spadefoots' ephemeral breeding ponds have been getting colder at most elevations, and male calls have been slowing as a result. However, temperature-standardized call characters have become faster, and male condition has increased, possibly due to changes in the selective environment. Thus, climate change might generate rapid, complex changes in sexual signals with important evolutionary consequences.

Chromosomes in the African frog genus Tomopterna (Pyxicephalidae) and probing the origin of tetraploid Tomopterna tandyi.

Speciation by polyploidization has been documented to have independently occurred in 12 families of anuran amphibians. Tomopterna tandyi was described as a South African allotetraploid species of sand frogs in the family Pyxicephalidae. Recent taxonomic revisions and new species descriptions in the genus present problems with respect to the evolution of this tetraploid species. Chromosomes, mitochondrial and nuclear gene sequences, isozymes, and male mating calls were examined for T. tandyi and for diploid species of Tomopterna. Mitochondrial sequences confirmed the diploid species, T. adiastola, to be the maternal ancestor that gave rise to the tetraploid about 5 mya. Nuclear sequences and isozymes reveal a complex reticulation of paternal ancestry that may be explained by occasional hybridization of T. tandyi with diploid species of Tompoterna at various times in sympatric populations. Interspecific diploid to tetraploid gene introgression is suspected to have also occurred in Australian and North American tetraploid species of frogs. Diploid to tetraploid introgression is facilitated through triploid hybrids that are more viable than diploid hybrids and produce unreduced triploid eggs.

Directional passive acoustic structures inspired by the ear of Achroia grisella

The need for small directional microphones is patent in the current market. From smartphones to hearing aids, a small microphone capable of rejecting ambient noise is highly desirable. Most MEMS microphones are omnidirectional and have to resort to arrays to achieve directionality, effectively counteracting the reduced size that they offer in the first place. For this reason, we use bio-inspiration and turn to nature to find examples of solutions to this problem. The female specimens of the moth Achroia grisella are capable of monoaural directional hearing, which they use to track the males’ mating calls. It is believed that they achieve directionality solely due to the morphology of their tympana. To test it, we first produce a multiphysics simulation of the structure that serves as a starting point. For experimental measurements, additive manufacturing is chosen for its ease and cost-efficiency. 3D-printed samples of the same model are examined through micro-CT scanning and then measured using laser-Doppler vibrometry to determine their frequency and directivity responses. The results of both approaches are compared, and it is found that the structure does indeed show directionality with the second eigenfrequency showing a hypercardioid-like pattern towards the front of the moth.

Older males whistle better: Age and body size are encoded in the mating calls of a nest-building amphibian (Anura: Leptodactylidae)

Courtship acoustic displays in anuran amphibians are energetically costly and risky, but have a major role in mating success since they encode relevant information regarding the caller’s identity and status. Age and size are essential traits shaping fitness, reproductive success and life-history strategies, and thus are expected to also have a role in courtship displays. We tested this assumption in a species of nest-building frogs,Leptodactylus bufonius, in northern Argentina. We conducted the first detailed quantitative description of the males’ mating calls and assessed the effects of biological traits (i.e., body size parameters and individual age) and local climate (i.e., air temperature and humidity) on the main acoustic features of these calls (i.e., call duration, inter-call duration, dominant frequency, and dominant frequency modulation). The calls were short (mean ± SE, 0.163 ± 0.004 s), whistle-like, single notes with harmonic structure. The dominant frequency (1381.7 ± 16.2 Hz) decreased with arm length (χ2= 5.244, df = 1,p= 0.022) and had an upward modulation (456.4 ± 11.0 Hz) which increased with age (χ2= 4.7012, df = 1,p= 0.030). Call duration and dominant frequency were the most static parameters at intra-individual level, indicating their role in individual recognition. Temperature and humidity shaped the temporal acoustic parameters, and the dominant frequency. Our findings suggest that the acoustic features of the mating calls in amphibians could promote female mate choice in relation to both size and age and open up new questions for future research: are females more attracted to older males, and what are the specific costs and benefits? We suggest that mating calls may direct female preferences toward males of certain size and age classes, ultimately shaping the life-history strategies in a given population. Finally, we found discrepancies in the mating calls ofL. bufoniusrecorded from Corrientes and those previously described from other populations, which suggests that multiple species may have been recorded under the same name.

Multisensory integration facilitates perceptual restoration of an interrupted call in a species of frog

Abstract Communication signals by both human and non-human animals are often interrupted in nature. One advantage of multimodal cues is to maintain the salience of interrupted signals. We studied a frog that naturally can have silent gaps within its call. Using video/audio-playbacks, we presented females with interrupted mating calls with or without a simultaneous dynamic (i.e., inflating and deflating) vocal sac and tested whether multisensory cues (noise and/or dynamic vocal sac) inserted into the gap can compensate an interrupted call. We found that neither inserting white noise into the silent gap of an interrupted call nor displaying the dynamic vocal sac in that same gap restored the attraction of the call equivalent to that of a complete call. Simultaneously presenting a dynamic vocal sac along with noise in the gap, however, compensated the interrupted call, making it as attractive as a complete call. Our results demonstrate that the dynamic visual sac compensates for noise interference. Such novel multisensory integration suggests that multimodal cues can provide insurance against imperfect sender coding in a noisy environment, and the communication benefits to the receiver from multisensory integration may be an important selective force favoring multimodal signal evolution.

The effects of environmental cues on chorusing onset in a tropical frog assemblage

Abstract There are extensive studies on frog calling behaviours, including the effects of environmental variables, however, there are no known studies to explore the specific proximate cues that stimulate the onset of calling in an individual on a given night. The aim of this study is to identify and quantify the species-specific set of environmental variables that stimulate males to produce mating calls under natural conditions. Call surveys were conducted at an active breeding pond on the edge of Parque Nacional Soberanía, Panama, during the breeding seasons of 2009 and 2010. Observations were made on 20 anuran species at the study site and we examined the onset of calling in nine species that were active and most consistently present during breeding seasons. We used logistic and linear regression models to investigate environmental conditions that affect calling for each species. The initiation of chorusing differed by species and key factors included ambient light, rainfall, and lunar cycle. Our data define the margins of a behavioural-environmental envelope that is species-specific and is not related to calling behaviour itself but is rather defined by physiological constraints related to environmental exposure.

Interval-counting neurons allow gray treefrogs to make the right choice

At the right time of year across the eastern USA, from Texas to Maine, wetlands come alive with the sound of trilling eastern gray treefrogs (Hyla versicolor), each hoping to attract the attention of a nearby female. However, male eastern gray treefrogs are not the only vociferous suitors in the neighbourhood; they share their wetland breeding grounds with another close relative, Cope's gray treefrogs (Hyla chrysoscelis). ‘The two species are visually indistinguishable’, says Saumya Gupta from the University of Minnesota, USA. Yet, the consequences of a Cope's gray treefrog inadvertently selecting an eastern gray treefrog partner would be disastrous; their offspring rarely survive and, if they do, they are infertile. Fortunately, eastern and Cope's gray treefrogs barely make this rookie mistake, thanks to their trilling croaks. Even though the trill structures of their amorous calls are similar, they are sufficiently different – eastern gray treefrogs trill a little more slowly than their Cope's cousins – for females to avoid selecting the wrong mate. Yet, no one was sure exactly how these closely related species distinguish between each other's trills. However, Gupta and Mark Bee (University of Minnesota) had a hunch. They knew that a unique set of neurons in frog brains – called interval-counting neurons – are often tuned to the trill rate of their own species’ calls. Could these neurons hold the key to female eastern gray treefrogs rebuffing Cope's gray treefrog serenades and vice versa?Collecting female gray treefrogs in amorous embraces with their male partners from the Tamarack Nature Center in Minnesota, USA, Gupta first had to identify which species each frog belonged to. ‘I played mating calls of the eastern and Cope's gray treefrogs from two separate loudspeakers and identified the species based on which speaker it approached’, she says. Next, Gupta simulated a series of gray treefrog trills composed of individual pulses – 10 ms pulses, 20 ms apart for the Cope's gray treefrogs and 30 ms pulses separated by 60 ms for the eastern gray treefrogs. After recreating the distinctive pulse signatures of both species, she played a range of trills to the females, from a single pulse up to 16 repetitions, recording the number of pulses when the female's attention switched from indifference to attraction as she hopped toward the loudspeaker.Comparing the females’ reactions, it was clear that the Cope's gray treefrogs tended to become interested in trills composed of ∼8, 10 ms pulses when the calls were softer (65 dB SPL) while trills of ∼7.5 pulses became attractive when louder (85 dB SPL). In contrast, the eastern gray treefrog females only required ∼5, 30 ms pulses to get their attention, falling to 3.5 pulses when the volume was higher. But how would the interval-counting neurons in the treefrog brain respond to each species-specific serenade?This time, Rishi Alluri and Gary Rose from the University of Utah, USA, played simulated trills with increasing numbers of pulses to the frogs while painstakingly recording when interval-counting neurons in the frog brain began sending electrical nerve signals. Eventually, the duo identified a subset of neurons in the Cope's gray treefrog brain tuned to fire when they heard trills of at least 6–8, 10 ms pulses. Meanwhile, the eastern gray treefrogs’ interval-counting neurons responded strongly when the frogs heard trills containing at least 3–5, 30 ms pulses.‘Interval-counting neurons play key roles in decoding information about species identity in frogs’, says Gupta, placing the neurons at the hub of the mechanism protecting eastern and Cope's gray treefrogs from interbreeding, keeping them faithful to their own species’ serenades.

Inter-sexual multimodal communication during mating in wild geladas: the leading role of females.

Female primates can emit vocalizations associated with mating that can function as honest signals of fertility. Here, we investigated the role of mating calls and visual signals in female geladas (Theropithecus gelada). Because females have a central role in the gelada society and seem to solicit sexual interactions, we answered whether they emit vocalizations in conjunction with gazing to increase mating success probability. Before and during copulations, females can emit pre-copulation calls and copulation calls. For the first time, we identified a new female vocalization emitted at the final stage of copulations (end-copulation call), possibly marking the occurrence of ejaculation. We found that longer pre-copulation call sequences were followed by both prolonged copulations and the presence of end-copulation calls, thus suggesting that females use pre-copulation calls to ensure successful copula completion. Moreover, we found that different combinations of female vocal types and gazing had different effects on male vocal behavior and motivation to complete the copula. The analysis of the vocal and visual signals revealed a complex inter-sexual multimodal chattering with the leading role of females in the signal exchange. Such chattering, led by females, modulates male sexual arousal, thus increasing the probability of the copula success.

On the vocal repertoire of the monkey frog Phyllomedusa venusta: distress call and the presumed non-existing advertisement call

ABSTRACT The anuran advertisement call has been widely used in taxonomic and evolutionary studies due to its essential role in species-specific recognition. For a long time, it has been presumed that P. venusta did not emit mating calls. Here, we observed the entire vocal activity period of P. venusta over the night and recorded male calls and a female distress call. We recognized and described a single male call type, identified as the advertisement call. This call has an extremely low timbre, and it is composed of a single or a sequence of pulsed notes. The multi-noted calls were usually emitted in intrasexual agonistic contexts. Although both call duration and note number have a high coefficient of variation values, they are linearly correlated, so they should be acting as a single independent variable in the P. venusta calls. As expected, the distress call is longer and with a higher timbre than the advertisement call. Interspecific comparisons were made based on the ratio between advertisement call dominant frequency (DF) and body size. This ratio is similar to those of the species of the P. tarsius group.

More than meets the eye: decrypting diversity reveals hidden interaction specificity between frogs and frog‐biting midges

1. Female frog‐biting midges (Diptera: Corethrellidae) eavesdrop on the nocturnal mating calls of their blood hosts – male frogs. Available data suggest variable degrees of specialisation among Corethrella‐host associations, with limited information on the mechanisms involved in host selection and partitioning on a community level.2. Our study provides a first comprehensive analysis of host interactions for a neotropical community of frog‐biting midges, based on both morphological and molecular genetic species delimitation. We used quantitative bipartite interaction networks to investigate host specificity among the midge‐frog community of La Gamba, Pacific lowland Costa Rica.3. Midges that were collected directly from frog hosts (16 frog species) showed more pronounced levels of specificity (network‐wide degree of specialisation: H2′ = 0.3) than those caught with acoustic traps broadcasting their calls (12 frog species; H2′ = 0.08). This indicates that, despite a rather generalist acoustic foraging behaviour, frog‐biting midges discriminate between potential hosts by using additional close‐range recognition cues.4. Based on COI and ITS2 sequencing data, we identified considerable levels of cryptic diversity within our five Corethrella morphotypes, with at least 17 distinct MOTUs of Corethrella in La Gamba. Including these MOTUs in bipartite network analyses produced higher resolution in species interactions, and increased estimators of network specificity (H2′ = 0.42).

Taxonomic revision of south-eastern Australian giant burrowing frogs (Anura: Limnodynastidae: Heleioporus Gray).

The rarely encountered giant burrowing frog, Heleioporus australiacus, is distributed widely in a variety of sclerophyll forest habitats east of the Great Dividing Range in south-eastern Australia. Analyses of variation in nucleotide sequences of the mitochondrial ND4 gene and thousands of nuclear gene SNPs revealed the presence of two deeply divergent lineages. Multivariate morphological comparisons show the two lineages differ in body proportions with > 91% of individuals being correctly classified in DFA. The two lineages differ in the number and size of spots on the lateral surfaces and the degree by which the cloaca is surrounded by colour patches. The mating calls are significantly different in number of pulses in the note. The presence of a F2 hybrid in the area where the distribution of the two taxa come into closest proximity leads us to assign subspecies status to the lineages, as we have not been able to assess the extent of potential genetic introgression. In our sampling, the F2 hybrid sample sits within an otherwise unsampled gap of ~90km between the distributions of the two lineages. The nominate northern sub-species is restricted to the Sydney Basin bioregion, while the newly recognised southern subspecies occurs from south of the Kangaroo Valley in the mid-southern coast of New South Wales to near Walhalla in central Gippsland in Victoria. The habitat of the two subspecies is remarkably similar. Adults spend large portions of their lives on the forest floor where they forage and burrow in a variety of vegetation communities. The southern subspecies occurs most commonly in dry sclerophyll forests with an open understory in the south and in open forest and heath communities with a dense understory in the north of its distribution. The northern subspecies is also found in dry open forests and heaths in association with eroded sandstone landscapes in the Sydney Basin bioregion. Males of both taxa call from both constructed burrows and open positions on small streams, differing from the five Western Australian species of Heleioporus where males call only from constructed burrows. Using the IUCN Red List process, we found that the extent of occupancy and area of occupancy along with evidence of decline for both subspecies are consistent with the criteria for Endangered (A2(c)B2(a)(b)).