Bioacoustic Characteristics Research Articles

Acoustic properties reconstruction of forehead tissues in an Indo-Pacific humpback dolphin (Sousa chinensis), with investigation on temperature effects on the species tissues sound velocity and beam

Computed tomography (CT) imaging and ultrasound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of forehead tissues from a deceased Indo-Pacific humpback dolphin (Sousa chinensis). The nonlinear regression methods were used to demonstrate the relationships between the sound velocity and temperature in melon, muscle and connective tissue. The obtained nonlinear equations were then combined with the original CT scanning results and sound velocity distributions reconstructed at room temperature 25°C to reconstruct the dolphin head’s sound velocity distribution at temperature 37°C. The beam formation and beam properties between two temperatures 37°C and 25°C were then compared and discussed. The results could provide important information for understanding the species’ bioacoustic characteristics and the acoustic data can be used for investigation of biosonar beam formation of this species.

An integrative approach to reveal speciation and species richness in the genusDiasporus(Amphibia: Anura: Eleutherodactylidae) in eastern Panama

We have applied an integrative taxonomic approach, including bioacoustics, ecology, morphology, and molecular genetics (barcoding and phylogeography), to explore species richness in the genus Diasporus in eastern Panama, from where only Diasporus quidditus (Lynch, 2001) was previously known. During fieldwork in eastern Panama in 2011 and 2012 we found six additional species, four of which we are describing here as new to science, plus two species that are new for this region. We have evaluated the presence of Diasporus diastema (Cope, 1875) in eastern Panama by comparing morphological, genetic, and bioacoustic characters of specimens from near the type locality in central Panama with specimens from eastern Panama. We further describe and compare male advertisement calls of most Diasporus species. The phylogeographic analysis suggests the allopatric speciation of Diasporus species in eastern Panama following the completion of the Panamanian isthmus in the middle Miocene. Subsequent geological events concur with the vicariant evolution of different lineages in situ, suggesting eastern Panama to be a centre of endemism for this group of frogs. We present an integrative analysis of the species from eastern Panama and include an identification key for all species of the genus.

Acoustic property reconstruction of a pygmy sperm whale (Kogia breviceps) forehead based on computed tomography imaging.

Computed tomography (CT) imaging and sound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of the forehead tissues of a deceased pygmy sperm whale (Kogia breviceps). The forehead was segmented along the body axis and sectioned into cross section slices, which were further cut into sample pieces for measurements. Hounsfield units (HUs) of the corresponding measured pieces were obtained from CT scans, and regression analyses were conducted to investigate the linear relationships between the tissues' HUs and velocity, and HUs and density. The distributions of the acoustic properties of the head at axial, coronal, and sagittal cross sections were reconstructed, revealing that the nasal passage system was asymmetric and the cornucopia-shaped spermaceti organ was in the right nasal passage, surrounded by tissues and airsacs. A distinct dense theca was discovered in the posterior-dorsal area of the melon, which was characterized by low velocity in the inner core and high velocity in the outer region. Statistical analyses revealed significant differences in density, velocity, and acoustic impedance between all four structures, melon, spermaceti organ, muscle, and connective tissue (p < 0.001). The obtained acoustic properties of the forehead tissues provide important information for understanding the species' bioacoustic characteristics.

Revision and phylogeny of narrow-mouthed treefrogs (Cophyla) from northern Madagascar: integration of molecular, osteological, and bioacoustic data reveals three new species.

We provide a revision of microhylid treefrogs of the genus Cophyla, the type genus of the subfamily Cophylinae. A phylogeny inferred from DNA sequences of multiple mitochondrial and nuclear genes, with representatives of all cophyline genera except Madecassophryne and including representatives of the two most divergent intrageneric lineages within Cophyla, placed Cophyla as sister group of Platypelis and confirmed both genera as reciprocally monophyletic. We describe three new Cophyla species based on osteological, morphological and bioacoustic characters as well as genetic differentiation in one nuclear and several mitochondrial markers. As in the vast majority of cophylines, all species of Cophyla emit long, stereotyped repetitions of a single tonal note, and we here consider one of these notes as a call; call duration thus equals note duration and the intervals between calls are named inter-call intervals. Cophyla maharipeo sp. nov. collected in Joffreville and Forêt d'Ambre Special Reserve (adult SVL 22-27 mm) is characterized by having long calls (1166-1346 ms) with long inter-call intervals (2154-3881 ms). Cophyla noromalalae sp. nov. collected in Montagne d'Ambre National Park (adult SVL 22-29 mm) is characterized by having short calls (662-821 ms) and short inter-call intervals (874-1882 ms). Cophyla puellarum sp. nov., also from Montagne d'Ambre National Park, is larger than the other two species (adult SVL 27.3-33.6 mm) and characterized by the shortest calls (326-390 ms) and long inter-call intervals (1961-3996 ms). Osteological analyses based on micro-CT scans and cleared and stained specimens confirms that the shape of the posterior vomer (centrally divided vs. undivided) may be a useful character to diagnose most species as belonging to either Platypelis and Cophyla, and suggest the absence of clavicles (present in Platypelis) is a derived character of most Cophyla. However, clavicles were present in C. puellarum, the only known Cophyla occurring at relatively high elevations (1250-1300 m a.s.l.) while otherwise in northern Madagascar, forests at higher elevations up to 2700 m a.s.l. are occupied by Platypelis species. Cophyla maharipeo was found at relatively low elevations (630-720 m a.s.l.), similar to the three previously known congeners (C. berara, C. occultans, C. phyllodactyla). Cophyla noromalalae occurs at intermediate elevations (900-1050 m a.s.l.). The molecular phylogeny inferred herein suggests that the ancestor of a clade containing all Cophyla species except C. puellarum evolved a modified shoulder girdle structure without ossified clavicles, and adapted to low-elevation habitats.

Optimizing passive acoustic sampling of bats in forests.

Passive acoustic methods are increasingly used in biodiversity research and monitoring programs because they are cost-effective and permit the collection of large datasets. However, the accuracy of the results depends on the bioacoustic characteristics of the focal taxa and their habitat use. In particular, this applies to bats which exhibit distinct activity patterns in three-dimensionally structured habitats such as forests. We assessed the performance of 21 acoustic sampling schemes with three temporal sampling patterns and seven sampling designs. Acoustic sampling was performed in 32 forest plots, each containing three microhabitats: forest ground, canopy, and forest gap. We compared bat activity, species richness, and sampling effort using species accumulation curves fitted with the clench equation. In addition, we estimated the sampling costs to undertake the best sampling schemes. We recorded a total of 145,433 echolocation call sequences of 16 bat species. Our results indicated that to generate the best outcome, it was necessary to sample all three microhabitats of a given forest location simultaneously throughout the entire night. Sampling only the forest gaps and the forest ground simultaneously was the second best choice and proved to be a viable alternative when the number of available detectors is limited. When assessing bat species richness at the 1-km2 scale, the implementation of these sampling schemes at three to four forest locations yielded highest labor cost-benefit ratios but increasing equipment costs. Our study illustrates that multiple passive acoustic sampling schemes require testing based on the target taxa and habitat complexity and should be performed with reference to cost-benefit ratios. Choosing a standardized and replicated sampling scheme is particularly important to optimize the level of precision in inventories, especially when rare or elusive species are expected.

Repeated call types in Hawaiian melon-headed whales (Peponocephala electra).

Melon-headed whales are pantropical odontocetes that are often found near oceanic islands. While considered sound-sensitive, their bioacoustic characteristics are relatively poorly studied. The goal of this study was to characterize the vocal repertoire of melon-headed whales to determine whether they produce repeated calls that could assist in recognition of conspecifics. The first tag-based acoustic recordings of three melon-headed whales were analyzed. Tag records were visually and aurally inspected and all calls were individually extracted. Non-overlapping calls with sufficient signal-to-noise were then parameterized and visually grouped into categories of repeated call types. Thirty-six call categories emerged. Categories differed significantly in duration, peak and centroid frequency, and -3 dB bandwidth. Calls of a given type were more likely to follow each other than expected. These data suggest that repeated calls may function in individual, subgroup, or group recognition. Repeated call production could also serve to enhance signal detection in large groups with many individuals producing simultaneous calls. Results suggest that caution should be used in developing automatic classification algorithms for this species based on small sample sizes, as they may be dominated by repeated calls from a few individuals, and thus not representative of species- or population-specific acoustic parameters.

The use of bioacoustic characters for distinguishing between cryptic species in insects: Potentials, restrictions, and prospects

Differences in acoustic signal patterns between closely related species often form the main precopulatory reproductive barrier in insects. For this reason, discrimination between similar forms based on their signal patterns allows one to recognize reproductively isolated species. A calling signal produced by a mature male for attracting a conspecific female is a “species ID” testifying to the fact that it belongs to the same species. This is the reason why the use of the calling signal analysis for discriminating between cryptic species or elucidating the taxonomic rank of dubious forms is highly efficient. In certain species, courtship signals also show species-specific patterns. In insect taxonomy, the study of acoustic signals is most promising in morphologically or/and ecologically heterogeneous groups. Chances that any morphologically homogeneous form will actually appear to be a complex of cryptic species are low. The degree of signal variability differs in different orders, families and even congeneric species. Therefore, in every taxon investigated for the first time, it is necessary to evaluate the limits of intraspecific variability of signals before using the acoustic characters in taxonomy. Species not involved in acoustic interactions due to allopatry, different host specialization, etc. can produce calling signals with identical patterns. Consequently, similarity in the signal structure in such species is by no means evidence of their synonymy.

Landscape connectivity, habitat structure and activity of bat guilds in farmland‐dominated matrices

Summary Agricultural intensification has caused a decline in structural elements in European farmland, where natural habitats are increasingly fragmented. The loss of habitat structures has a detrimental effect on biodiversity and affects bat species that depend on vegetation structures for foraging and commuting. We investigated the impact of connectivity and configuration of structural landscape elements on flight activity, species richness and diversity of insectivorous bats and distinguished three bat guilds according to species‐specific bioacoustic characteristics. We tested whether bats with shorter‐range echolocation were more sensitive to habitat fragmentation than bats with longer‐range echolocation. We expected to find different connectivity thresholds for the three guilds and hypothesized that bats prefer linear over patchy landscape elements. Bat activity was quantified using repeated acoustic monitoring in 225 locations at 15 study plots distributed across the Swiss Central Plateau, where connectivity and the shape of landscape elements were determined by spatial analysis (GIS). Spectrograms of bat calls were assigned to species with the software batit by means of image recognition and statistical classification algorithms. Bat activity was significantly higher around landscape elements compared to open control areas. Short‐ and long‐range echolocating bats were more active in well‐connected landscapes, but optimal connectivity levels differed between the guilds. Species richness increased significantly with connectivity, while species diversity did not (Shannon's diversity index). Total bat activity was unaffected by the shape of landscape elements. Synthesis and applications. This study highlights the importance of connectivity in farmland landscapes for bats, with shorter‐range echolocating bats being particularly sensitive to habitat fragmentation. More structurally diverse landscape elements are likely to reduce population declines of bats and could improve conditions for other declining species, including birds. Activity was highest around optimal values of connectivity, which must be evaluated for the different guilds and spatially targeted for a region's habitat configuration. In a multi‐species approach, we recommend the reintroduction of structural elements to increase habitat heterogeneity should become part of agri‐environment schemes.

Calls and tadpoles of the species of Lysapsus (Anura, Hylidae, Pseudae)

Larval and bioacoustical characters are crucial for anuran systematics. Nevertheless, advertisement calls and larval morphology of most Neotropical anuran species are unknown. Lysapsus is a peculiar group of aquatic frogs that have been subject to recurrent taxonomic changes. Recent molecular phylogenetic and external morphology work gave support for some of the recognized species (L. laevis and L. caraya), but considerable doubt remains over the distinction among L. limellum and L. bolivianus. We describe the tadpoles of L. caraya and L. bolivianus, the advertisement call of L. laevis, and redescribe the advertisement calls of L. caraya, L. limellum, and L. bolivianus. Our results support the genus based on larval and bioacoustical characters. Lysapsus caraya and L. laevis have distinct advertisement calls, but no visual or statistically significant differences were observed between advertisement calls of L. limellum and L. bolivianus. Tadpoles of L. caraya, L. limellum, and L. bolivianus are similar based on external morphology and contrast against the distinct tadpole of L. laevis. Considerable doubt is raised on the validity of L. bolivianus, which either is a junior synonym of L. limellum or constitutes a cryptic species based on currently available data. Data on osteology, musculature, and chondrocranium, allied to robust phylogeographic analyses will help clarify the taxonomic status of these two putative species and the biogeographic relationships between the Amazon and the Paraná River basins.

The use of bioacoustic characters for distinguishing between cryptic species in insects: potentials, restrictions, and prospects

The use of bioacoustic characters for distinguishing between cryptic species in insects: potentials, restrictions, and prospects

Phylogeny of the Emballonurini (Emballonuridae) with descriptions of a new genus and species from Madagascar

Abstract Molecular phylogenetic studies suggest that the genus Emballonura, a member of the Old World tribe Emballonurini (Family Emballonuridae), is paraphyletic. This genus has a broad distribution across islands in the Indo-Pacific, southern Asia, and Madagascar. The paraphyly is the result of the genus Coleura, known from sub-Saharan Africa, portions of the Arabian Peninsula, Madagascar, and the Seychelles, being embedded between the Malagasy and Asian/Indo-Pacific clades of Emballonura, and the latter clade has priority for the use of the name. To resolve this situation, we propose a new genus for the Malagasy Emballonura clade. Furthermore, with greater molecular sampling of Coleura across portions of its range in association with morphological and bioacoustical characters, we are able to resolve aspects of the phylogenetic history and species limits of this genus. Coleura contains two well supported clades, including C. afra from mainland Tanzania and the offshore island of Pemba and a sister clade...

A tiny new species of Platypelis from the Marojejy National Park in northeastern Madagascar (Amphibia: Microhylidae)

We describe a tiny new frog species of the genus Platypelis (Anura: Microhylidae: Cophylinae) from Marojejy National Park, northeastern Madagascar. Platypelis ravus sp. nov. differs from all other known Platypelis and Cophyla species by its small size (17-19 mm snout-vent length) and a combination of other morphological and bioacoustic characters. The new species seems to be most closely related to P. milloti with which it shares the principal colour pattern, but exhibits a yellow rather than red posterior venter. Uncorrected pairwise sequence divergence in a 16S rRNA gene fragment to all other known species of the genus (except P. cowanii for which no genetic data is available) is greater than 6%. We suggest the inclusion of the new species in the IUCN threat category “Data Deficient”.

Platycleis galvagnii, a peculiar new bushcricket from Sardinia (Italy) (Insecta, Orthoptera, Tettigoniidae)

Platycleis galvagnii n. sp. from Sardinia (Italy) is described. In general habitus the new taxon is close to Platycleis sensu strictu, albeit very small in size. When looking at other characters the species does not seem to fit within one of the groups recognised within Platycleis s.l., but for the moment the species is placed in Platycleis s.s.. The species is characterised by a range of morphological and bioacoustic characters. Its real affiliations with other species within the Platycleis complex need to be established further. For the moment the species is known only from the type locality, Gennargentu mountain in the central part of Sardinia.

Integrative taxonomy reveals cryptic Amazonian species ofPristimantis(Anura: Strabomantidae)

Hypotheses on the taxonomic status of two Bolivian Pristimantis with taxonomic problems are assessed by an integrative taxonomic approach that integrates three independent lines of evidence: external morphology, prezygotic reproductive barriers (advertisement calls) and reciprocal monophyly (phylogenetic analyses of partial 16S mtDNA sequences). Central Andean Bolivian populations previously assigned to either P. peruvianus or P. dundeei, and lowland Amazonian populations from southern Peru and northern Bolivia previously considered P. peruvianus do not correspond to these species. Indeed, multivariate analyses of qualitative and quantitative morphological and bioacoustic characters, and phylogenetic analyses support the hypothesis that they represent different, previously unknown, cryptic lineages. They are herein described as new species. The former is a sibling species of P. fenestratus that inhabits the Amazonian and semideciduous forests of the Andean foothills in central Bolivia. The latter is sibling to the Andean species P. danae and is parapatric to it in the Amazonian lowland forests and adjacent foothills of northern Bolivia, southern Peru and adjacent Brazil. Most species of Neotropical frogs, and especially Pristimantis, have been described by using external qualitative morphological characters only. An extended integrative taxonomic approach, as exemplified herein, may lead to the discovery of many other cryptic and sibling lineages that would increase the species numbers of tropical areas.

Morphological and Bioacoustic Characteristics of Frogs of the Genus Platymantis (Amphibia, Ranidae) in Irian Jaya, with Descriptions of Two New Species

On the basis of museum collections and field work, new discoveries were made concerning the morphology, distribution, bioacoustics and ecology of the hitherto New Guinean species Platymantis papuensis, P. punctata and P. batantae. Moreover, two species, Platymantis cryptotis and Platymantis bimaculata, are described as new. Eventual evolutionary relationships among Papuan Platymantis species are discussed. It is supposed that P. punctata is the most primitive of the Platymantis species from New Guinea and adjacent islands. Species pairs with derived characters are P. batantae and P. bimaculata as well as P. papuensis and P. cryptotis.

The possibility to use bioacoustic characters in the taxonomy of the jumping plant lice with an example of the genus Craspedolepta (Homoptera, Psyllinea, Aphalaridae) and description of a new species from Transbaikalia

Oscillograms of calling signals of 14 species of Craspedolepta s. l. are presented. Temporal patterns of the signals in representatives of different species groups are quite similar. Therefore, the use of acoustic characters for distinguishing between genera and subgenera of psyllids appears to be impossible. In certain cases, the structure of signals in different species is almost identical. Nonetheless, in strictly sympatric species occurring in the same territory and living on the host plants of the same species, i.e., involved into acoustic interactions with each other, the signal pattern is always distinctly different. Consequently, the similarity of signals can be considered evidence of the synonymy only in sympatric forms dwelling on the same host plant. On the other hand, distinct differences in the signal patterns indicate conclusively that the forms investigated possess the rank of species. Craspedolepta filifoliae sp. n. collected in the steppe of Transbaikalia on Filifolium sibiricum is described and illustrated. The new species is closely related to the widespread C. malachitica, but differs from it in the pattern of the fore wings and certain details of the genitalia structure. Besides, distinct differences in acoustic characters between these forms provide strong evidence that C. filifoliae sp. n. is a separate (valid) species.

Molecular phylogeny of Malagasy reed frogs, Heterixalus, and the relative performance of bioacoustics and color-patterns for resolving their systematics

The members of the genus Heterixalus constitute one of the endemic frog radiations in Madagascar. Here we present a complete species-level phylogeny based on DNA sequences (4876 base pairs) of three nuclear and four mitochondrial markers to clarify the phylogenetic relationships among and within all known species of this genus, as well as the phylogenetic position of the monospecific Seychellean Tachycnemis seychellensis. Although the performance to resolve supported clades of Heterixalus species differed among the investigated gene fragments when analyzed separately, we could identify five well-supported species groups within Heterixalus in the combined analysis of all gene fragments. Our data strongly support a Heterixalus– Tachycnemis clade, and indicate the probable monophyly of Heterixalus placed sister to Tachycnemis. However, the diversification of these lineages may have happened in a short interval of time, leading to an unstable placement of Tachycnemis in the single-gene fragment phylogenies. Referring to the hitherto existing classification of Heterixalus, which is predominantly based on chromatic and bioacoustic characters, we examined the relative performance of these data sets relative to our molecular phylogeny. A Bayesian tree reconstructed with a bioacoustic data set yielded a higher resemblance to the molecular phylogeny than a tree constructed using a chromatic data set, which supports the importance of bioacoustic characters for systematic analyses of these anurans.

Morphological and Bioacoustic Characteristics of Frogs of the GenusPlatymantis (Amphibia, Ranidae) in Irian Jaya, with Descriptions of Two New Species

Morphological and Bioacoustic Characteristics of Frogs of the GenusPlatymantis (Amphibia, Ranidae) in Irian Jaya, with Descriptions of Two New Species

Shifts in sound features of the duetting pallid swiftsApus pallidusL.

Bioacoustic characteristics of the screaming calls of the pallid swift (Apus pallidus) emitted by the breedings pairs in antiphonal sequence were studied. The calls alternate with precise time intervals. In 441 of our records each individual maintains constant spectrographic characteristics, while in 562 a mate shifts its sound features on to the partner ones. It is suggested that the last part of the call maintains the highest personal features allowing vocal individual recognition, and that the calls have a territorial function against conspecific intrusion in the nest-holes of the breeding pair.