High-Pitched Notes during Vocal Contests Signal Genetic Diversity in Ocellated Antbirds

University of Sussex, United Kingdom
PLoS ONE (Impact Factor: 3.23). 12/2009; 4(12):e8137. DOI: 10.1371/journal.pone.0008137
Source: PubMed


Animals use honest signals to assess the quality of competitors during aggressive interactions. Current theory predicts that honest signals should be costly to produce and thus reveal some aspects of the phenotypic or genetic quality of the sender. In songbirds, research indicates that biomechanical constraints make the production of some acoustic features costly. Furthermore, recent studies have found that vocal features are related to genetic diversity. We linked these two lines of research by evaluating if constrained acoustic features reveal male genetic diversity during aggressive interactions in ocellated antbirds (Phaenostictus mcleannani). We recorded the aggressive vocalizations of radiotagged males at La Selva Biological Station in Costa Rica, and found significant variation in the highest frequency produced among individuals. Moreover, we detected a negative relationship between the frequency of the highest pitched note and vocalization duration, suggesting that high pitched notes might constrain the duration of vocalizations through biomechanical and/or energetic limitations. When we experimentally exposed wild radiotagged males to simulated acoustic challenges, the birds increased the pitch of their vocalization. We also found that individuals with higher genetic diversity (as measured by zygosity across 9 microsatellite loci) produced notes of higher pitch during aggressive interactions. Overall, our results suggest that the ability to produce high pitched notes is an honest indicator of male genetic diversity in male-male aggressive interactions.

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    • "Little Spotted Kiwi have lower genetic diversity than Brown Kiwi and all other species of kiwi (Ramstad et al. 2010), and this may be reflected in their lower vocal diversity. Genetic diversity is related to song diversity or structure in birds at an individual level (Marshall et al. 2003; Seddon et al. 2004; Pfaff et al. 2007; Araya-Ajoy et al. 2009; McDonald and Wright 2011) and also at a population level (Robin et al. 2011). Is it therefore feasible that a relation between genetic and call diversity exists at the species level in kiwi, providing at least a partial explanation for the differences in vocal diversity between LSK and Brown Kiwi? "
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    ABSTRACT: The ability to identify individuals by call is particularly important for monitoring cryptic or nocturnal species. It provides key benefits in conservation management, such as allowing correction of biases in censuses and monitoring individual survival. Call surveys are a key tool in conservation of kiwi (Apterygidae), yet individuality of calls has previously been assessed in just one of the five species, the Brown Kiwi (formerly North Island Brown Kiwi, Apteryx mantelli). We have made the first test of whether Little Spotted Kiwi (Apteryx owenii; LSK) can be individually identified by call. Three classification methods (discriminant function analysis, support vector machines and statistical classifiers) were used to assign identity from either call or syllable variables. Using syllables, classification was significantly better than expected by chance for both males and females. Individual LSK can therefore be identified acoustically, suggesting that vocalisations may be used for conspecific identification. Classifier performance was worse using call variables, with no better than chance assignment for females and low accuracy for males. Significant differences in classification ability between the sexes support the hypothesis that the function of calls of male and female LSK differ. Furthermore, identification by call was much less reliable in LSK than in the more genetically diverse Brown Kiwi. This indicates that call diversity may be related to genetic diversity in kiwi, which, if confirmed, could provide a powerful conservation tool for rapid assessment of genetic differences among populations of these threatened species.
    The Emu: official organ of the Australasian Ornithologists' Union 01/2014; 114(4). DOI:10.1071/MU13114 · 1.11 Impact Factor
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    • "Importantly, these quivers associated with sound production provide a stimulus that can be detected by both the inner ear and mechanosensory lateral line system, but how this information might be differentially used by the female remains unknown. Since many of the acoustic characteristics associated with sound production are energetically expensive, they likely function as honest signals used during mate choice, as demonstrated in other vertebrate and invertebrate taxa [80], [81], [82]. However, it is also likely that other non-intended receivers, both males and females, in the vicinity of a courting male can eavesdrop on the sounds and use it to gain social, spawning, or feeding opportunities. "
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    ABSTRACT: Sexual reproduction in all animals depends on effective communication between signalers and receivers. Many fish species, especially the African cichlids, are well known for their bright coloration and the importance of visual signaling during courtship and mate choice, but little is known about what role acoustic communication plays during mating and how it contributes to sexual selection in this phenotypically diverse group of vertebrates. Here we examined acoustic communication during reproduction in the social cichlid fish, Astatotilapia burtoni. We characterized the sounds and associated behaviors produced by dominant males during courtship, tested for differences in hearing ability associated with female reproductive state and male social status, and then tested the hypothesis that female mate preference is influenced by male sound production. We show that dominant males produce intentional courtship sounds in close proximity to females, and that sounds are spectrally similar to their hearing abilities. Females were 2-5-fold more sensitive to low frequency sounds in the spectral range of male courtship sounds when they were sexually-receptive compared to during the mouthbrooding parental phase. Hearing thresholds were also negatively correlated with circulating sex-steroid levels in females but positively correlated in males, suggesting a potential role for steroids in reproductive-state auditory plasticity. Behavioral experiments showed that receptive females preferred to affiliate with males that were associated with playback of courtship sounds compared to noise controls, indicating that acoustic information is likely important for female mate choice. These data show for the first time in a Tanganyikan cichlid that acoustic communication is important during reproduction as part of a multimodal signaling repertoire, and that perception of auditory information changes depending on the animal's internal physiological state. Our results highlight the importance of examining non-visual sensory modalities as potential substrates for sexual selection contributing to the incredible phenotypic diversity of African cichlid fishes.
    PLoS ONE 05/2012; 7(5):e37612. DOI:10.1371/journal.pone.0037612 · 3.23 Impact Factor
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    • "Recent years have seen a wealth of papers describing heterozygosity–fitness correlations (HFCs) in which heterozygosity , usually measured at around 10 microsatellite markers, is shown to predict some aspect of an individual's fitness. The direction of the relationship seems almost invariably to be in the direction of higher heterozygosity indicating higher quality, and the traits studied embrace almost all aspects of life, from birth weight (Coulson et al. 1999) and parasite resistance (Rijks et al. 2008) though recruitment and reproductive and success (Amos et al. 2001; Cohas et al. 2009) to plumage coloration (Foerster et al. 2003), song pitch (Araya-Ajoy et al. 2009), attractiveness (Hoffman, Forada, et al. 2007), dominance status (Tiira et al. 2006) and territory holding ability (Höglund et al. 2002). As such, HFCs appear to represent an important component of fitness in many or perhaps even most systems. "
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    ABSTRACT: Although heterozygosity-fitness correlations (HFCs) are widely reported in the literature, most studies use too few markers to allow the proximate mechanisms to be convincingly resolved. Two competing hypotheses have been proposed: the general effect hypothesis, in which marker heterozygosity correlates with genome-wide heterozygosity and hence the inbreeding coefficient f, and the local effect hypothesis, in which one or more of the markers by chance exhibit associative overdominance. To explore the relative contributions of general and local effects in a free-ranging marine mammal population, we revisited a strong HFC found using 9 microsatellite loci for canine tooth size in 84 male Antarctic fur seals Arctocephalus gazella (Hoffman JI, Hanson N, Forcada J, Trathan PN, Amos W. 2010. Getting long in the tooth: a strong positive correlation between canine size and heterozygosity in the Antarctic fur seal Arctocephalus gazella. J Hered.). Increasing the number of markers to 76, we find that heterozygosity is uncorrelated across loci, indicating that inbred individuals are rare or absent. Similarly, while the HFC based on overall heterozygosity is lost, stochastic simulations indicate that when an HFC is due to inbreeding depression, increasing marker number invariably strengthens the HFC. Together these observations argue strongly that the original HFC was not due to inbreeding depression. In contrast, a subset of markers show individually significant effects, and these are nonrandomly distributed across the marker panel, being preferentially associated with markers cloned from other species. Using basic alignment search tool searches, we were able to locate 94% of loci to unique locations in the dog genome, but the local genes are functionally diverse, and the majority cannot be linked directly to growth. Our results suggest that inbreeding depression contributes little if at all to the relationship between heterozygosity and tooth size but that instead the primary mechanism involves associative overdominance. These findings contribute to a growing body of evidence suggesting that general effects are likely to be uncommon in natural populations.
    The Journal of heredity 05/2010; 101(5):539-52. DOI:10.1093/jhered/esq046 · 2.09 Impact Factor
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