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Behavioural response of a migratory songbird to geographic variation in song and morphology.

Mortega KG, Flinks H, Helm B - Front. Zool. (2014)

Bottom Line: Time to approach increased, and time spent close to the stimuli and number of tail flips decreased consistently with geographic distance of the stimulus from the local population.Song traits of the local population differed significantly from those of other populations.We have demonstrated that in both sexes of Stonechats the responsiveness to acoustic and visual signals decreased with increasing geographic distance of stimulus origin.

View Article: PubMed Central - PubMed

Affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany ; Department of Ornithology, University of Konstanz, 78457 Konstanz, Germany ; Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G12 8QQ Glasgow, UK.

ABSTRACT

Introduction: Sexually selected traits contribute substantially to evolutionary diversification, for example by promoting assortative mating. The contributing traits and their relevance for reproductive isolation differ between species. In birds, sexually selected acoustic and visual signals often undergo geographic divergence. Clines in these phenotypes may be used by both sexes in the context of sexual selection and territoriality. The ways conspecifics respond to geographic variation in phenotypes can give insights to possible behavioural barriers, but these may depend on migratory behaviour. We studied a migratory songbird, the Stonechat, and tested its responsiveness to geographic variation in male song and morphology. The traits are acquired differently, with possible implications for population divergence. Song can evolve quickly through cultural transmission, and thus may contribute more to the establishment of geographic variation than inherited morphological traits. We first quantified the diversity of song traits from different populations. We then tested the responses of free-living Stonechats of both sexes to male phenotype with playbacks and decoys, representing local and foreign stimuli derived from a range of distances from the local population.

Results: Both sexes discriminated consistently between stimuli from different populations, responding more strongly to acoustic and morphological traits of local than foreign stimuli. Time to approach increased, and time spent close to the stimuli and number of tail flips decreased consistently with geographic distance of the stimulus from the local population. Discriminatory response behaviour was more consistent for acoustic than for morphological traits. Song traits of the local population differed significantly from those of other populations.

Conclusions: Evaluating an individual's perception of geographic variation in sexually selected traits is a crucial first step for understanding reproductive isolation mechanisms. We have demonstrated that in both sexes of Stonechats the responsiveness to acoustic and visual signals decreased with increasing geographic distance of stimulus origin. These findings confirm consistent, fine discrimination for both learned song and inherited morphological traits in these migratory birds. Maintenance or further divergence in phenotypic traits could lead to assortative mating, reproductive isolation, and potentially speciation.

No MeSH data available.


Related in: MedlinePlus

Playback experiment in males. Behavioural response for (a) latency to approach, (b) time spent within 5 m, and (c) number of tail flips in response to European Stonechats from (1) the local population, (2) a population from 90 km distance, (3) a population from 180 km distance, (4) African stonechats, and (5) control stimuli (Winter wren). Males discriminated between local and foreign stimuli by responding more strongly to song of their own population. Box plots represent, from bottom to top: minimum, lower quartile, median, upper quartile and maximum. Dots indicate observations further than one s.d. away from the mean; n =28.
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Fig2: Playback experiment in males. Behavioural response for (a) latency to approach, (b) time spent within 5 m, and (c) number of tail flips in response to European Stonechats from (1) the local population, (2) a population from 90 km distance, (3) a population from 180 km distance, (4) African stonechats, and (5) control stimuli (Winter wren). Males discriminated between local and foreign stimuli by responding more strongly to song of their own population. Box plots represent, from bottom to top: minimum, lower quartile, median, upper quartile and maximum. Dots indicate observations further than one s.d. away from the mean; n =28.

Mentions: Stonechats of the local population responded differently to stimuli from distinct populations, measured by the time they took to approach the caller or decoy (i.e., latency to approach within 5 m). In response to playback, males discriminated significantly between origins of the stimulus (z = −8.42, p <0.001, Table 2a, Figure 2). The males’ latency to approach the caller was lowest when exposed to the local song and increased with distance of stimulus origin (Table 2a, Figure 2). Breeding stage, trial order (Additional file 1: Figure S4), date and time of day showed no significant effect on the males’ latency to approach (Table 2a).Table 2


Behavioural response of a migratory songbird to geographic variation in song and morphology.

Mortega KG, Flinks H, Helm B - Front. Zool. (2014)

Playback experiment in males. Behavioural response for (a) latency to approach, (b) time spent within 5 m, and (c) number of tail flips in response to European Stonechats from (1) the local population, (2) a population from 90 km distance, (3) a population from 180 km distance, (4) African stonechats, and (5) control stimuli (Winter wren). Males discriminated between local and foreign stimuli by responding more strongly to song of their own population. Box plots represent, from bottom to top: minimum, lower quartile, median, upper quartile and maximum. Dots indicate observations further than one s.d. away from the mean; n =28.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4256809&req=5

Fig2: Playback experiment in males. Behavioural response for (a) latency to approach, (b) time spent within 5 m, and (c) number of tail flips in response to European Stonechats from (1) the local population, (2) a population from 90 km distance, (3) a population from 180 km distance, (4) African stonechats, and (5) control stimuli (Winter wren). Males discriminated between local and foreign stimuli by responding more strongly to song of their own population. Box plots represent, from bottom to top: minimum, lower quartile, median, upper quartile and maximum. Dots indicate observations further than one s.d. away from the mean; n =28.
Mentions: Stonechats of the local population responded differently to stimuli from distinct populations, measured by the time they took to approach the caller or decoy (i.e., latency to approach within 5 m). In response to playback, males discriminated significantly between origins of the stimulus (z = −8.42, p <0.001, Table 2a, Figure 2). The males’ latency to approach the caller was lowest when exposed to the local song and increased with distance of stimulus origin (Table 2a, Figure 2). Breeding stage, trial order (Additional file 1: Figure S4), date and time of day showed no significant effect on the males’ latency to approach (Table 2a).Table 2

Bottom Line: Time to approach increased, and time spent close to the stimuli and number of tail flips decreased consistently with geographic distance of the stimulus from the local population.Song traits of the local population differed significantly from those of other populations.We have demonstrated that in both sexes of Stonechats the responsiveness to acoustic and visual signals decreased with increasing geographic distance of stimulus origin.

View Article: PubMed Central - PubMed

Affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany ; Department of Ornithology, University of Konstanz, 78457 Konstanz, Germany ; Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G12 8QQ Glasgow, UK.

ABSTRACT

Introduction: Sexually selected traits contribute substantially to evolutionary diversification, for example by promoting assortative mating. The contributing traits and their relevance for reproductive isolation differ between species. In birds, sexually selected acoustic and visual signals often undergo geographic divergence. Clines in these phenotypes may be used by both sexes in the context of sexual selection and territoriality. The ways conspecifics respond to geographic variation in phenotypes can give insights to possible behavioural barriers, but these may depend on migratory behaviour. We studied a migratory songbird, the Stonechat, and tested its responsiveness to geographic variation in male song and morphology. The traits are acquired differently, with possible implications for population divergence. Song can evolve quickly through cultural transmission, and thus may contribute more to the establishment of geographic variation than inherited morphological traits. We first quantified the diversity of song traits from different populations. We then tested the responses of free-living Stonechats of both sexes to male phenotype with playbacks and decoys, representing local and foreign stimuli derived from a range of distances from the local population.

Results: Both sexes discriminated consistently between stimuli from different populations, responding more strongly to acoustic and morphological traits of local than foreign stimuli. Time to approach increased, and time spent close to the stimuli and number of tail flips decreased consistently with geographic distance of the stimulus from the local population. Discriminatory response behaviour was more consistent for acoustic than for morphological traits. Song traits of the local population differed significantly from those of other populations.

Conclusions: Evaluating an individual's perception of geographic variation in sexually selected traits is a crucial first step for understanding reproductive isolation mechanisms. We have demonstrated that in both sexes of Stonechats the responsiveness to acoustic and visual signals decreased with increasing geographic distance of stimulus origin. These findings confirm consistent, fine discrimination for both learned song and inherited morphological traits in these migratory birds. Maintenance or further divergence in phenotypic traits could lead to assortative mating, reproductive isolation, and potentially speciation.

No MeSH data available.


Related in: MedlinePlus