Hybrid Songs Research Articles

Fin whale song evolution in the North Atlantic.

Animal songs can change within and between populations as the result of different evolutionary processes. When these processes include cultural transmission, the social learning of information or behaviours from conspecifics, songs can undergo rapid evolutions because cultural novelties can emerge more frequently than genetic mutations. Understanding these song variations over large temporal and spatial scales can provide insights into the patterns, drivers and limits of song evolution that can ultimately inform on the species' capacity to adapt to rapidly changing acoustic environments. Here, we analysed changes in fin whale (Balaenoptera physalus) songs recorded over two decades across the central and eastern North Atlantic Ocean. We document a rapid replacement of song INIs (inter-note intervals) over just four singing seasons, that co-occurred with hybrid songs (with both INIs), and a clear geographic gradient in the occurrence of different song INIs during the transition period. We also found gradual changes in INIs and note frequencies over more than a decade with fin whales adopting song changes. These results provide evidence of vocal learning in fin whales and reveal patterns of song evolution that raise questions on the limits of song variation in this species.

Strange Tunes—Acoustic Variation and Character Displacement in a Tarsier Hybrid Zone

Natural hybridization provides valuable insights into evolutionary processes, such as speciation and the forces driving or hindering it. Sulawesi tarsiers Tarsius dentatus and T. lariang hybridize within a limited area, suggesting selection against hybrids. Their species- and sex-specific duet songs might serve as a premating barrier in sympatry, especially if differences are strengthened by character displacement. Individuals of mixed origin might face disadvantages if they inherit intermediate song traits. To shed light on the processes shaping this hybrid zone, we analysed 55 duet songs from within and outside the zone. For females and males, we identified temporal and frequency-related parameters that differ between species. We inspected hybrid songs for intermediate characteristics and analysed purebred songs for character displacement in sympatry. Female hybrid songs (N = 2) were intermediate in four to five of six parameters; interpretation of male hybrid songs (N = 2) was inconclusive, because only two parameters were reliably quantifiable. There was no character displacement in female songs in sympatry (N = 11) compared with monospecific areas (N = 17). In male songs, interspecific differences in note rate were significantly larger within the hybrid zone (N = 8) compared with outside (N = 13). Intermediate song traits indicate inheritance and may disadvantage hybrids during mate choice. Character displacement in male songs is consistent with female mate choice, because females should opt for unmistakable signals to avoid costly hybridization. Our findings thus suggest that duet songs of T. lariang and T. dentatus play an important role in limiting this hybrid zone.

Blue Notes 2.0: The Diachronic Resonance of Langston Hughes During the George Floyd Protests: A Foreword

Blue Notes 2.0: The Diachronic Resonance of Langston Hughes During the George Floyd Protests: A Foreword

Inside Arabic Music: Arabic Maqam Performance and Theory in the 20th Century

Inside Arabic Music: Arabic Maqam Performance and Theory in the 20th Century

Singing-in-between spaces: Bhooter Bhabisyat and the music transcending class conflict

This article analyses Bhooter Bhabisyat, a Bengali political horror satire, as a counter-narrative to Bengali cinema’s monocultural bhodrolok branding. The article argues that Bhooter Bhabisyat is radical in its refusal to follow hegemonic homogenizing musical styles classified into genres such as folk, popular, traditional and modern, which tend to be ethnocentric and class based with serious value judgments about the superiority of certain musical forms over others. Instead, Bhooter Bhabisyat uses a variety of distinct Bengali musical traditions to problematize the historic role of capitalist media that work to homogenize and popularize the dominant culture of the ruling classes. The hybrid songs of the film disrupt a sense of homogeneous bhodrolok class position that Bengali cinema has historically sustained. Through the strategies of musical pastiche, Bhooter Bhabisyat offers a meta-historic narrative about Bengali cinema, which makes possible a critical investigation of the cultural discourses and historical narratives that are discursively embedded within the history of filmic production, circulation and consumption. If film histories are produced by repressing differences between social groups and constructing universal identification, then foregrounding film songs as decolonial storytelling methods that reemphasize local voices and subject matters can lead to an effort to read history from below. The vulgar representation of time as a precise and homogeneous continuum has […] diluted the Marxist concept of history. (Giorgio Agamben) The history of all hitherto existing society is the history of class struggles. (Karl Marx)

Migratory convergence facilitates cultural transmission of humpback whale song.

Cultural transmission of behaviour is important in a wide variety of vertebrate taxa from birds to humans. Vocal traditions and vocal learning provide a strong foundation for studying culture and its transmission in both humans and cetaceans. Male humpback whales (Megaptera novaeangliae) perform complex, culturally transmitted song displays that can change both evolutionarily (through accumulations of small changes) or revolutionarily (where a population rapidly adopts a novel song). The degree of coordination and conformity underlying song revolutions makes their study of particular interest. Acoustic contact on migratory routes may provide a mechanism for cultural revolutions of song, yet these areas of contact remain uncertain. Here, we compared songs recorded from the Kermadec Islands, a recently discovered migratory stopover, to multiple South Pacific wintering grounds. Similarities in song themes from the Kermadec Islands and multiple wintering locations (from New Caledonia across to the Cook Islands) suggest a location allowing cultural transmission of song eastward across the South Pacific, active song learning (hybrid songs) and the potential for cultural convergence after acoustic isolation at the wintering grounds. As with the correlations in humans between genes, communication and migration, the migration patterns of humpback whales are written into their songs.

Song variation of the South Eastern Indian Ocean pygmy blue whale population in the Perth Canyon, Western Australia.

Sea noise collected over 2003 to 2017 from the Perth Canyon, Western Australia was analysed for variation in the South Eastern Indian Ocean pygmy blue whale song structure. The primary song-types were: P3, a three unit phrase (I, II and III) repeated with an inter-song interval (ISI) of 170–194 s; P2, a phrase consisting of only units II & III repeated every 84–96 s; and P1 with a phrase consisting of only unit II repeated every 45–49 s. The different ISI values were approximate multiples of each other within a season. When comparing data from each season, across seasons, the ISI value for each song increased significantly through time (all fits had p << 0.001), at 0.30 s/Year (95%CI 0.217–0.383), 0.8 s/Year (95%CI 0.655–1.025) and 1.73 s/Year (95%CI 1.264–2.196) for the P1, P2 and P3 songs respectively. The proportions of each song-type averaged at 21.5, 24.2 and 56% for P1, P2 and P3 occurrence respectively and these ratios could vary by up to ± 8% (95% CI) amongst years. On some occasions animals changed the P3 ISI to be significantly shorter (120–160 s) or longer (220–280 s). Hybrid song patterns occurred where animals combined multiple phrase types into a repeated song. In recent years whales introduced further complexity by splitting song units. This variability of song-type and proportions implies abundance measure for this whale sub population based on song detection needs to factor in trends in song variability to make data comparable between seasons. Further, such variability in song production by a sub population of pygmy blue whales raises questions as to the stability of the song types that are used to delineate populations. The high level of song variability may be driven by an increasing number of background whale callers creating ‘noise’ and so forcing animals to alter song in order to ‘stand out’ amongst the crowd.

Behind the Green Door: Unpacking the Item Number and Its Ecology

The term ‘item numbers’ emerged in film journalism sometime in the late 1990s as an industry slang. It later evolved into a heterogeneous cinematic language with its investment in production design, choreography, special effects and specialised editing. Using interviews with industry professionals, this article will unpack the production ecology of the hypersexualised and hybrid song and dance spectacle.

A new Neotibicen cicada subspecies (Hemiptera: Cicadidae) from the southeastern USA forms hybrid zones with a widespread relative despite a divergent male calling song.

A morphologically cryptic subspecies of Neotibicen similaris (Smith and Grossbeck) is described from forests of the Apalachicola region of the southeastern United States. Although the new form exhibits a highly distinctive male calling song, it hybridizes extensively where it meets populations of the nominate subspecies in parapatry, by which it is nearly surrounded. This is the first reported example of hybridization between North American nonperiodical cicadas. Acoustic and morphological characters are added to the original description of the nominate subspecies, and illustrations of complex hybrid song phenotypes are presented. The biogeography of N. similaris is discussed in light of historical changes in forest composition on the southeastern Coastal Plain.

A narrow hybrid zone between the grasshoppersStenobothrus clavatusandStenobothrus rubicundus(Orthoptera: Gomphocerinae): female preferences for courtship songs

Two grasshopper species, Stenobothrus rubicundus and Stenobothrus clavatus, were previously shown to hybridize in a narrow contact zone on Mount Tomaros in northern Greece. The species are characterized by complex and completely different courtship songs. In the present study, we investigated female preferences for the courtship songs of S. rubicundus, S. clavatus and hybrids in playback experiments. Playback of the courtship songs revealed assortative preferences in females of the parental species: they significantly more often preferred the songs of conspecific males. Hybrid females showed a lower selectivity than parental females, responding somewhat equally eager to playback of the songs of S. clavatus, S. rubicundus, and natural hybrid song, although less actively to the F1 hybrid song. The results suggest that hybrid males may lose to males of parental species, whereas hybrid females would even have an advantage over parental females. Comparison of responses of females from allopatric populations and Mount Tomaros to different song types shows no evidence for reinforcement. Asymmetry found in female preferences may have implications for the structure of the hybrid zone. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 108, 834–843.

A narrow hybrid zone between the grasshoppers Stenobothrus clavatus and Stenobothrus rubicundus: courtship song analysis

The closely related grasshopper species Stenobothrus rubicundus and Stenobothrus clavatus are known to hybridize in a very narrow contact zone on Mt. Tomaros in northern Greece. These species produce very different and complex courtship songs accompanied with visual display. We analyzed the courtship songs and underlying stridulatory movements of the hind legs in natural hybrids from Mount Tomaros. The two species were also hybridized in the laboratory and their songs were compared with the songs of the natural hybrids. Some hybrid songs were shown to have intermediate features between parental songs, whereas other hybrid songs comprised completely new elements. The clavatus-like song elements were found to dominate in hybrid songs. These song features may influence the mating success of hybrid males in the contact zone. A comparison of hybrid songs with the song pattern of the north European S. rubicundus populations allowed us to suggest a scenario of S. rubicundus and S. clavatus origin.

What exactly is ‘local song’ in a population of ortolan buntings with a common dialect?

Previous studies have shown that ortolan buntings (Emberiza hortulana) exhibit apparent dialect variation. Neighbouring males typically share the same final phrase of a simple two-part song. Consequently, the final phrase was considered to be the dialect cue important for discriminating between males from a local population and strangers. Recently, it was shown that in an isolated and fragmented population of the ortolan buntings in Norway there was no local dialect in the above-mentioned sense. Norwegian males often had song types with different final phrases in their repertoire, and had larger repertoires and a lower level of song type sharing than in other populations. It was experimentally revealed that only local songs (L) evoked a strong response in Norwegian males, while these birds did not respond strongly to foreign (F) or hybrid songs composed of local and foreign initial and final phrases in any composition (i.e. both FL and LF songs). These results suggest that, in the Norwegian population, the final phrase of the song is not a sufficient cue for local song dialect recognition. This paper is a further study in which we tested the response of the ortolan bunting males to L, F, FL and LF songs in a typical continuous population (in Poland) in which males share the same single final phrase, i.e. have a common dialect. We found that ortolan bunting males in Poland responded with similar strength to L, FL and LF songs. The majority of males did not respond as strongly to playback of only F songs. Our results suggest that a common final phrase for a population should not be treated as the only signal of ‘locality’. Our results show clear asymmetry in response to hybrid songs with non-local phrases in different populations.

Acoustic niche partitioning in two cryptic sibling species of Chrysoperla green lacewings that must duet before mating

Cryptic species may seem identical to us, but not to each other. The Chrysoperla carnea group of green lacewings has species-specific substrate-borne duetting songs that maintain reproductive isolation among its cryptic species. We propose that sympatric species of the group will partition acoustic niche space so as to minimize mating mistakes. Sibling species pairs could therefore occupy abutting regions of acoustic space without hybridizing in nature. One species pair, Chrysoperla plorabunda and C. adamsi, are not only closest relatives, but are also the most acoustically similar among sympatric congeners. Using F1 hybrids as a surrogate taxon occupying acoustic space between the parents, we tested the hypothesis that this space cannot support an additional species. Focusing on a critical song feature, volley period, we confirm firstly that the hybrid song occupies unfilled signal space between the parents. Secondly, we show that song discrimination is strong between parents, but weaker between parents and hybrids. Thirdly, each parent has the ability to respond to the other’s signal in a narrow region of overlap. Finally, preference functions for hybrids broadly overlap those of parents. These acoustic tests confirm that a species of this intermediate song phenotype could not persist.

What makes a ‘local song’ in a population of ortolan buntings without a common dialect?

Ortolan buntings, Emberiza hortulana , have local dialects in central and southern Europe. Neighbouring males typically share the same final phrase of a song, which seems to be important for dialect recognition. We studied ortolan buntings in Norway, where a small and isolated population occurs with no local dialect in the above-mentioned sense. Norwegian males often have song types with different final phrases in their repertoire, and have larger repertoires and less song type sharing than other populations. We experimentally tested (1) whether male ortolan buntings from Norway discriminate between local and foreign or hybrid songs, and (2) what part of the song is used to discriminate between local and foreign songs. We studied the response to typical local songs (L), conspecific foreign songs from a remote population (F), and computer-created hybrid songs with a local final phrase and foreign initial phrase (F–L) and vice versa (L–F). Only local songs evoked a strong response, measured as latency to flight and approach, number of flights and closest distance from the loudspeaker. For F, F–L and L–F song playbacks, the majority of males did not respond at all, or responded significantly less than to L songs. Our results suggest that at least in this population, the final phrase of the song is not a sufficient cue for local song dialect recognition. We discuss the adaptive value of discriminating between own and foreign songs based on specific cues versus full songs in relation to dispersal and song-learning pattern in the ortolan bunting.

Behavioral sterility of hybrid males in acoustically communicating grasshoppers (Acrididae, Gomphocerinae)

The effectiveness of hybridization barriers determines whether two species remain reproductively isolated when their populations come into contact. We investigated acoustic mating signals and associated leg movements responsible for song creation of hybrids between the grasshopper species Chorthippus biguttulus and C. brunneus to study whether and how songs of male hybrids contribute to reproductive isolation between these sympatrically occurring species. Songs of F1, F2, and backcross hybrids were intermediate between those of both parental species in terms phrase number and duration. In contrast, species-specific syllable structure within phrases was largely lost in hybrids and was produced, if at all, in an irregular and imperfect manner. These divergences in inheritance of different song parameters are likely the result of incompatibility of neuronal networks that control stridulatory leg movements in hybrids. It is highly probable that songs of hybrid males are unattractive to females of either parental species because they are intermediate in terms of phrase duration and lack a clear syllable structure. Males of various hybrid types (F1, F2, and backcrosses) are behaviorally sterile because their songs fail to attract mates.

The unusual inheritance pattern of the courtship songs in closely related grasshopper species of the Chorthippus albomarginatus‐group (Orthoptera: Gomphocerinae)

Sibling species of the Chorthippus albomarginatus-group are exceptional among all European grasshopper species because they have an extremely elaborate courtship behaviour. Here, we present a genetic analysis of the courtship song differences between two closely related grasshopper species Ch. albomarginatus and Ch. oschei. Measurements of seven courtship song characters and one parameter of courtship visual display were compared among parentals, F(1) and F(2) hybrids, and backcrosses. Variation in one morphological character, the number of stridulatory pegs, was studied as well. The distributions of song phenotypes were more consistent with a type-III genetic architecture, which involves complementary or duplicate pairs of loci. We suggest that this type of architecture may provide the novel elements of the hybrid songs, even more complex than the parental ones, which may offer a new starting point for sexual selection. One parameter of the visual display appeared to be controlled by a single locus, but differences in other characters of visual display could be explained by a more complex inheritance pattern. Inheritance of the peg number differences was consistent with a simple polygenic additive model. Sex linkage and/or maternal effects were not detected for any trait. We found a disproportionate influence of the Ch. albomarginatus parent on most hybrid song characteristics and the visual display, and this may support a previously suggested idea that Ch. albomarginatus is an ancestral form and Ch. oschei is a derived species.

Partial song matching in an eastern population of song sparrows, Melospiza melodia

One hypothesis for the function of vocal repertoires in songbirds is that singing multiple song types facilitates song matching, a behaviour in which one male replies to a rival's song with a song of the same type. In eastern populations of song sparrows, low levels of whole song sharing restrict opportunities for matching of entire song types. A male in this population might still match a neighbour by replying with a partially shared song (i.e. a song that contains one or more phrases in common with the neighbour's song). We tested for partial matching in a Pennsylvania population using playback of three categories of song: self song (allowing a full match), stranger song (a control allowing no match) and hybrid self/stranger song (allowing a partial match). We also tested the hypothesis that matching is a directed signal of aggressive intentions by comparing subjects' approach distances between trials in which they did and did not match. Males in our study matched in response to both self song (21 of 39 trials) and hybrid song (23 of 40 trials) at levels significantly greater than expected based on control trials (5 of 40 trials). Males that performed a partial match to a hybrid song approached the speaker more closely than males that did not match, consistent with the hypothesis that partial matching is a directed signal of aggression. Self song matching did not predict approach as successfully.

Complex courtship in a bimodal grasshopper hybrid zone

Grasshoppers of the Chorthippus albomarginatus-group, which is outstanding with respect to its complex courtship song, were studied at fifteen localities in the Ukraine and Moldova. The analysis of the courtship songs revealed two species: C. albomarginatus in north-eastern Ukraine and Chorthippus oschei in the south-western Ukraine and Moldova. In a belt about 200 km wide, not only were one or the other pure species found, but also males with intermediate song characters. C. albomarginatus and C. oschei were hybridised in the laboratory, and F1 hybrid males as well as F2 hybrid males produced intermediate song patterns, quite similar to those recorded in the field. We defined a "hybrid song score" for intermediate songs. The score showed a bimodal distribution with most songs resembling one or other parental type, but with only a few intermediates. At several localities, where hybrids with songs similar to one of the parental species dominated, some individual males sang more similarly to the other species. In one locality, two hybrid populations only 3 km apart had different parental types. Hybrid songs can contain novel elements, even more complex than the parental ones, which may offer a new starting point for sexual selection. We suggest that genetic introgression occurs between the two sibling species C. albomarginatus and C. oschei within a wide hybrid zone stretching over a distance of several hundred kilometres, but with a patchy spatial distribution.

Phonology and Geographic Song Discrimination in Song Sparrows

AbstractWe investigated whether song sparrows discriminate foreign from local songs using specific phonologic markers, a mechanism of geographic discrimination previously described for some other songbirds. Song sparrows from Linesville, Pennsylvania (PA) respond more strongly to local songs than to songs from Millbrook, New York (NY). We identify 61 note categories in PA and NY songs, of which 13 are unique to PA, 17 are unique to NY, and 31 are shared. The most common note category in PA song, ‘buzz BO5’, is present in 89% of PA songs and only in 8% of NY songs; this difference in percentage representation is the largest we found for any note category. Substituting this potential PA marker into NY songs, however, did not make those songs more salient to PA sparrows; instead, PA males tested with territorial playback responded significantly less aggressively to NY/PA hybrid songs than to NY songs. A series of control experiments showed that song sparrows do not detect substitution of PA notes into PA songs or of NY notes into NY songs. The results weigh against the hypothesis that geographic discrimination in song sparrows is accomplished simply by recognition of a small number of phonologic markers.

Vibratory songs of hybrids from Brazilian and Slovenian populations of the green stink bug Nezara viridula

Vibratory songs of hybrids from Brazilian and Slovenian populations of the green stink bug Nezara viridula