05392nas a2200265 4500008004100000245008800041210006900129520457700198653002404775653002704799653000904826653001304835653002504848653002804873653001904901653002104920653002704941653001304968653001804981653002404999653001505023653001505038100003205053856004105085 2020 eng d00aDivergent selection and reproductive isolation: an empirical study on reed buntings0 aDivergent selection and reproductive isolation an empirical stud3 a

Divergent selection and local adaptation are responsible for many phenotypic differences between populations, potentially leading to speciation through the evolution of reproductive barriers. Acoustic divergence, in particular, is often the basis of assortative mating and behavioral isolation in birds. However, some species have different singing styles used in distinct social contexts, and songs of each style may change at different rates over time and space. Mate recognition largely depends on learning, generally resulting in discrimination against nonlocal stimuli. Nevertheless, there may also be geographical variation in discrimination, allowing inference on the mechanisms behind recognition. Morphologic divergence can cause reproductive isolation too, and a strong association between bill traits and foraging niche, at a given place and time, may indicate ecological speciation is at play and how.
This thesis focused on reed buntings (Emberiza schoeniclus), a small passerine that breeds in marshlands throughout the Palearctic. Populations of three subspecies were studied: migratory E. s. schoeniclus, breeding in northern and central Europe; and the residents E. s. lusitanica from northwest Iberia and E. s. witherbyi from southeast Iberia and southern France (hereafter schoeniclus, lusitanica and witherbyi, respectively).
Four main objectives were addressed using different approaches: (1) phenotypic divergence was evaluated to determine the extent of local adaptation to migration and diet, using linear measurements and geometric morphometrics; (2) song divergence between subspecies and between the three singing styles of each subspecies were tested searching for effects of sexual selection, using spectral traits and derived synthetic variables; (3) song discrimination level was determined to infer premating reproductive isolation, using playback of fast song to test territorial males; (4) association between bill morphology and foraging niche was evaluated searching for evidence of natural selection, by sampling blood in southwest Europe during the winter (when target subspecies co-occur) and performing stable isotope analyses (carbon and nitrogen).
As predicted, migratory subspecies were smaller and had longer and more pointed wings. Unexpectedly, their tail was longer, probably due to correlation with wing length. witherbyi, which feed on insects hiding inside reed stems during the winter, had a very thick bill; whereas schoeniclus, which feed on seeds, had thinner bills. Although smaller, lusitanica had thicker and longer bill than schoeniclus. Geometric morphometrics revealed that southern subspecies have a more convex culmen than schoeniclus, and that lusitanica and schoeniclus bills differ more in shape than in linear measurements. The two singing styles under sexual selection (dawn and fast songs, related to obtaining extrapair and social mates, respectively) diverged more than the slow songs (an all-clear signal to nest attending females). Multiple song traits differed between subspecies in all styles, with intermediate values for lusitanica. Cluster analyses of populations indicate that sexually selected styles better discriminate subspecies, describing a major split in song features between schoeniclus and the resident subspecies. It was found that witherbyi, and to some extent lusitanica, males largely ignored schoeniclus songs. However, witherbyi reacted less strongly to lusitanica than the converse. In contrast, schoeniclus males reacted equally strongly to all subspecies. schoeniclus showed a broader isotopic niche than southern subspecies, which seemed similar despite witherbyi more divergent bill. Stable isotope ratios were consistent with resident subspecies feeding on C3-plant-feeding insects, whereas schoeniclus diet also included C4 plant material.

Subspecies differing in several traits as theoretically predicted indicate local adaptation through natural selection. Greater song divergence in fast and dawn styles implies that sexual selection is important in this evolutionary process. Differential territorial defense provides evidence of premating reproductive isolation, and discrimination by southern subspecies seems associated with local adaptation. Recognition pattern agrees with ecological rather than neutral divergence, as predicted in ecological speciation processes. Isotopic niche divergence between northern and southern subspecies suggests that bill differentiated by natural selection through competition during winter.

10aacoustic divergence10aasymmetric recognition10abill10abirdsong10aEmberiza schoeniclus10ageometric morphometrics10aisotopic niche10alocal adaptation10amorphologic divergence10aplayback10asinging style10asong discrimination10aspeciation10asubspecies1 aGordinho, Luís, de Oliveir uhttps://bio.acousti.ca/sv/node/5819802647nas a2200145 4500008004100000245016500041210006900206520203900275100002902314700002302343700002002366700001902386700002402405856007202429 2019 eng d00aExtraordinary variation in a simple song: No geographical patterns in initial phrase variation of the Yellowhammer, a passerine with pronounced dialectsAbstract0 aExtraordinary variation in a simple song No geographical pattern3 a

Geographical variation of birdsong is used to study various topics from cultural evolution to mechanisms responsible for reproductive barriers or song acquisition. In species with pronounced dialects, however, patterns of variation in non-dialect parts of the song are usually overlooked. We focused on the individually variable initial phrase of the song of the Yellowhammer (Emberiza citrinella), a common Palearctic passerine which became a model species for dialect research. We used a quantitative method to compare the similarity of initial phrases from the repertoires of 237 males recorded at different spatial scales in a central European country covering all main dialect types. We hypothesized that patterns of initial phrase sharing and/or phrase similarity are affected by dialect boundaries and geographical proximity (i.e. that birds from the same dialect regions use more similar phrases or share them more often). Contrary to our expectations, initial phrase variation seems unrelated to dialects, as we did not find higher similarity either among recordings from the same dialect areas or among those from the same locality. Interestingly, despite the immense variability of phrase types detected (only 16% of 368 detected initial phrase types were shared between at least 2 males), a relatively high proportion of males (45%) was involved in sharing, and males using the same initial phrase were located anywhere from tens of meters to hundreds of kilometers apart. The patterns of variation suggest that precise copying during song learning as well as improvisation play important roles in forming individual repertoires in the Yellowhammer. Our data also confirm previous indications that the repertoires of Yellowhammer males (i.e. the composition of initial phrases) are individually unique and temporally stable. This makes the species a good candidate for individual acoustic monitoring, useful for detailed population or behavioral studies without the need for physical capture and marking of males.

1 avan Boheemen, Sharina, J1 aDiblíková, Lucie1 aBílková, Jana1 aPetrusek, Adam1 aPetrusková, Tereza uhttps://academic.oup.com/auk/article/doi/10.1093/auk/ukz055/560144902360nas a2200205 4500008004100000245010700041210006900148260001600217300001400233490000800247520169800255653002301953653002001976653001401996653002402010100002702034700002402061700001502085856005402100 2018 eng d00aSoft songs in male ortolan buntings are used in an aggressive context but are not an aggressive signal0 aSoft songs in male ortolan buntings are used in an aggressive co cJan-08-2018 a549 - 5580 v1243 a

Many bird species produce low‐amplitude acoustic signals that have been poorly studied in comparison with loud, broadcast songs used for mate attraction and repelling rivals. In some birds, these soft signals were found to be emitted in an antagonistic context and were the most reliable predictor of a subsequent physical attack. The function of this signal is poorly understood, and several hypotheses have been proposed to explain the mechanisms and possible functions of such low‐amplitude signals. The subject of this study is the ortolan bunting, a small passerine species that produces soft songs during territorial defence. In this study, we aim to study whether the soft songs of the ortolan bunting are a signal of increased aggressiveness by testing if they meet the context, prediction and response criteria of aggressive signals. We simulated stranger male intrusion into a focal male territory with three different playback experiments. We found no significant differences in the male responses to the taxidermic model regardless of whether they were or were not producing soft songs in response. The males responded more strongly to loud songs than to soft songs during the simulated intrusions, and the males did not treat soft songs as a predictor of conflict escalation. Although soft songs clearly appeared during territorial encounters and were not present during spontaneous singing before the intrusions, our results did not support the hypothesis that soft songs indicate aggressive character. We suggest that soft songs in the ortolan bunting are intentionally used by birds to modify their intentions or target‐specific individuals within a close range.

10aAggressive signals10aortolan bunting10asoft song10aterritorial defence1 aJakubowska, Aleksandra1 aOsiejuk, Tomasz, S.1 aFusani, L. uhttp://doi.wiley.com/10.1111/eth.2018.124.issue-802625nas a2200205 4500008004100000022001300041245006400054210006400118260001600182300001400198490000800212520182300220653002302043653002302066653002402089653002202113100002702135700002402162856023302186 2018 eng d a0376635700aSing softly to evoke a response only from a recent intruder0 aSing softly to evoke a response only from a recent intruder cJan-12-2018 a244 - 2490 v1573 a

Low-amplitude soft songs have been described in many birds, but in most species, research has addressed only broadcast songs. Soft songs may have a similar or distinctive structure in comparison to broadcast songs produced in order to defend a territory and attract females. In some species, such soft songs were found to be produced in an aggressive context and were the best predictors of conflict escalation and later physical attack. However, such observations are not consistent across all species studied. Several hypotheses have been put forward to explain the function(s) of soft songs and why they are so quiet. Studies on the ortolan bunting (Emberiza hortulana) show that males produce soft songs similar in structure to broadcast songs during close interactions with conspecific intruders. However, experiments with the playback of loud and soft songs as well as taxidermic mount presentation revealed that soft song in this species does not fulfil aggressive signal criteria. Here we performed an experiment with two loudspeakers simulating movements of the intruder in order to test whether the soft songs are used to evoking a response from a nearby but not localised rival. We found that males responded with similar strength to songs played back from single and double speaker systems. Simultaneously, males produced more soft songs during and just after the phase of the experiment in which we simulated short flights of the intruder. Our results indicate that soft songs might be used during close interactions with rivals without being an aggressive signal and are used as short-range signals to check if the rival is still around. Our results also provide an alternative explanation of soft song behaviour in comparison to the hypotheses of eavesdropping avoidance and readiness to fight.

10aAggressive signals10aEmberiza hortulana10aplayback experiment10aTerritory defence1 aJakubowska, Aleksandra1 aOsiejuk, Tomasz, S. uhttps://linkinghub.elsevier.com/retrieve/pii/S0376635718301335https://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/plain