@mastersthesis {58198, title = {Divergent selection and reproductive isolation: an empirical study on reed buntings}, year = {2020}, abstract = {

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.

}, keywords = {acoustic divergence, asymmetric recognition, bill, birdsong, Emberiza schoeniclus, geometric morphometrics, isotopic niche, local adaptation, morphologic divergence, playback, singing style, song discrimination, speciation, subspecies}, author = {Lu{\'\i}s de Oliveira Rijo Gordinho} } @article {57661, title = {Anatomy of the stridulation apparatus of the beech leaf-mining weevil and characterization of, and behavioral responses to, stridulation sounds}, year = {2019}, abstract = {

We investigated auditory signals and morphology of the stridulatory apparatus of the European beech leaf-mining weevil, Orchestes fagi L. (Coleoptera: Curculionidae), an invasive herbivore now established in Nova Scotia, Canada, to determine their potential for enhancing survey tools to monitor the spread of the species in Canada. We recorded and described sounds produced by adult O. fagi, analyzed the morphology of the stridulatory mechanism for intersexual differences and asymmetry, and examined behavioral responses elicited in conspecifics by playback of stridulation recordings. Adult O. fagi produced sounds under three conditions: male in distress, female in distress, and male in the presence of female. Female distress chirps lasted significantly longer than male distress chirps and male chirps in the presence of females, but peak frequencies and mean number of chirps per s did not differ significantly among the three groups. Morphology of the stridulation structures in male and female O. fagi was compared using scanning electron microscopy. Orchestes fagi have an elytro-tergal file- and scraper-type sound production apparatus, through which sound is produced upon anterior motion of the abdomen. Female O. fagi have a \‘pars stridens\’ that is longer and has more ridges than males. Width and number of ridges per length of pars stridens did not differ between the sexes. Evidence of asymmetry was found in male pars stridens, with the right side being longer than the left. Playback of recorded sounds to adult weevils suggests female O. fagi were repelled by sounds produced by distressed males.

}, keywords = {auditory recording, beechweevil, Coleoptera, Curculionidae, distressstridulation, insectbehavior, insectbioacoustics, Orchestes fagi, pars stridens, playback, scanningelectron microscopy, sexual dimorphism}, doi = {10.1111/eea.12844}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/eea.12844}, author = {Goodwin, Joel T.L. and Hillier, N. Kirk and Roscoe, Lucas E. and Sweeney, Jon D.} } @article {57394, title = {Heterospecific alarm-call recognition in two warbler hosts of common cuckoos}, year = {2019}, abstract = {

Species facing similar selection pressures should recognize heterospecific alarm signals. However, no study has so far examined heterospecific alarm-call recognition in response to parasitism by cuckoos. In this study, we tested whether two sympatric host species of the common cuckoo Cuculus canorus, Oriental reed warbler Acrocephalus orientalis (ORW, main host), and black-browed reed warbler Acrocephalus bistrigiceps (BRW, rare host), could recognize each other\’s alarm calls in response to cuckoos. Dummies of common cuckoo (parasite) and Eurasian sparrowhawk Accipiter nisus (predator) were used to induce and record alarm calls of the two warbler species, respectively. In the conspecific alarm-call playback experiments, ORW responded more strongly to cuckoo alarm calls than to sparrowhawk alarm calls, while BRW responded less strongly to cuckoo alarm calls than to sparrowhawk alarm calls. In the heterospecific alarm-call playback experiments, both ORW and BRW responded less strongly to cuckoo alarm calls than sparrowhawk alarm calls. BRW seemed to learn the association between parasite-related alarm calls of the ORW and the cuckoo by observing the process of ORW attacking cuckoos. In contrast, alarm calls of BRW to cuckoos were rarely recorded in most cases. BRW with low parasite pressure still developed recognition of heterospecific parasite-related alarm call. Unintended receivers in the same community should recognize heterospecific alarm calls precisely to extract valuable information.

}, keywords = {alarm call, Brood parasitism, Heterospecific recognition, playback}, doi = {10.1007/s10071-019-01307-9}, url = {http://link.springer.com/10.1007/s10071-019-01307-9}, author = {Yu, Jiangping and Lu, Hailin and Sun, Wei and Liang, Wei and Wang, Haitao and Anders Pape M{\o}ller} } @article {53424, title = {The buzz segment of Savannah sparrow song is a population marker}, journal = {Journal of Ornithology}, year = {2018}, month = {Mar-12-2018}, abstract = {

Different components of learned birdsongs change at different rates across generations, and the rate of change may correspond to the information carried by each component. To characterize the role of the buzz segment of Savannah sparrow songs, we examined recordings from southeastern Canada and the northeastern US and fully characterized buzz segments in songs recorded from two populations: one on Kent Island, NB, Canada and another in Williamstown, MA, USA. Buzzes varied geographically: Kent Island buzzes had higher mean frequencies and shorter pulse periods than Williamstown buzzes and the differences between the two populations persisted over time. Population-specific buzz characteristics also appeared to be resistant to change. Variants appeared on Kent Island in the late 1980s and were learned by some younger birds; however, these buzz variants disappeared by 2011. We conducted a playback experiment and found that males from both populations had longer responses to local buzzes. Therefore, buzz structure varies geographically; population characteristics of the buzz persist through time despite the introduction of variant forms; and territorial males discriminate between buzzes from different populations. The learned buzz segment of the song may thus serve as a population marker for Savannah sparrows.

}, keywords = {Cultural evolution, dialect, Passerculus sandwichensis, playback, Population, song}, issn = {2193-7192}, doi = {10.1007/s10336-018-1611-7}, url = {http://link.springer.com/10.1007/s10336-018-1611-7}, author = {Williams, Heather and Robins, Clint W. and Newman, Amy E. M. and Freeman-Gallant, Corey R. and Wheelwright, Nathaniel T. and Mennill, Daniel J.} } @article {53398, title = {Social context-dependent provisioning rules in red-winged fairy-wrens do not vary with signals of increased chick need}, journal = {Animal Behaviour}, volume = {143}, year = {2018}, month = {Jan-09-2018}, pages = {105 - 111}, abstract = {

Individuals should adjust investment in parental care in order to maximize current and future reproductive success. In cooperative breeders, where helpers assist with raising offspring, larger groups may allow for a reduction in investment (load lightening) of each individual. Additionally, the type of individual, and thus the social context, can play an important role in individual investment. Less attention has been paid to how provisioning rules vary across ecological contexts, although theory suggests that individuals can only afford to reduce their investment when nestling starvation is unlikely, thus under mild conditions. Here, we tested whether previously reported provisioning rules based on social context vary with ecological conditions, by experimental manipulation of signals of chick need, in the cooperatively breeding red-winged fairy-wren, Malurus elegans. Previous work in this species has shown that all group members load-lighten with additional male helpers, but not in response to the number of female helpers in the group (additive care). We show that experimental begging playback resulted in all individuals increasing their provisioning rates, indicating that our treatment was perceived as increased chick need. However, in contrast to our prediction that load lightening should only occur when individuals can afford to do so, signals of increased chick need did not stop individuals from reducing their investment with an increasing number of male helpers in the group. These results suggest that despite some flexibility in parental effort, individuals use strict rules with respect to group composition, suggesting that individual provisioning effort is based on multiple integrated cues, and responses to changes in the environment are highly context dependent.

}, keywords = {additive care, cooperative breeding, helping behaviour, load lightening, Malurus, parental investment, playback}, issn = {00033472}, doi = {10.1016/j.anbehav.2018.07.010}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0003347218302252https://api.elsevier.com/content/article/PII:S0003347218302252?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0003347218302252?httpAccept=text/plain}, author = {MacLeod, K.J. and Brouwer, L.} } @article {53392, title = {Subspecies status and methods explain strength of response to local versus foreign song by oscine birds in meta-analysis}, journal = {Animal Behaviour}, volume = {142}, year = {2018}, month = {Jan-08-2018}, pages = {1 - 17}, abstract = {

To understand the implications of geographical variation in vocal culture in songbirds, researchers have often compared territorial responses to playback of local songs versus responses to playback of songs from \‘foreign\’ conspecifics. This body of work has the potential to help us move towards a general understanding of factors driving divergence in signal recognition. We conducted a systematic review and meta-analysis of 57 playback studies to explain variation in strength of response to local versus foreign songs. Studies with incomplete reporting of results had elevated effects due to selective reporting. Studies that used small numbers of stimuli as exemplars (pseudoreplication) had more variable effects than studies without severe pseudoreplication. Whether or not we controlled for pseudoreplication, we found greater response to playback of local song than to foreign song. In investigating potential biological drivers of the variation in strength of experimental effects, we found that the difference in territorial response to local versus foreign song was stronger if the foreign song was recorded from another subspecies than if the foreign song was recorded from the same subspecies as the focal individuals. Indexes of risk of accidental response to heterospecific song did not coherently explain response to foreign conspecific songs, nor did factors expected to influence individual experience with foreign conspecific songs. Thus, although oscine songbirds clearly react more aggressively to local song than to foreign song and variation in the strength of this effect is influenced by methodological choices and subspecies status, considerable variation in the strength of response to local versus foreign song playback remains to be explained.

}, keywords = {deceptive mimicry, meta-analysis, playback, pseudoreplication, selective reporting, signalling}, issn = {00033472}, doi = {10.1016/j.anbehav.2018.05.023}, url = {https://linkinghub.elsevier.com/retrieve/pii/S000334721830174Xhttps://api.elsevier.com/content/article/PII:S000334721830174X?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S000334721830174X?httpAccept=text/plain}, author = {Parker, Timothy H. and Emma I. Greig and Nakagawa, Shinichi and Parra, Marcelina and Dalisio, Anthony C.} }