| 1. |
- Andersson, Måns Sverker, et al.
(author)
-
A partly coverable badge signalling avian virus resistance
- 2006
-
In: Acta Zoologica. ; :87, s. 71-76
-
Journal article (peer-reviewed)abstract
- Abstract: We investigated whether the sexually selected forehead patch of the collared flycatcher Ficedula albicollis is an honest badge of status indicating quality expressed as immunological response. We used both manual measurements and digital measurements, the latter based on photographs. Badge-size data were collected during the mating period and during the nestling feeding period to capture trait plasticity. Concomitant with first sample collection, birds were inoculated with a novel antigen. Antibody response was strongly and positively correlated with badge expression during the mating period and with the increase in badge expression during the mating period as compared with outside this period. The results support the Hansen and Rohwer theory of coverable badges, are consistent with the immunocompetence handicap hypothesis and with the good genes model suggesting that, on a population level, the expression of secondary sexual traits should be an honest signal positively associated with traits that are beneficial for survival. The results also suggest that manual measurements of this type of secondary sexual trait are sufficiently exact.
|
|
| 2. |
- Boström, Jannika E., et al.
(author)
-
The flicker fusion frequency of budgerigars (Melopsittacus undulatus) revisited
- 2017
-
In: Journal of Comparative Physiology A. Sensory, neural, and behavioral physiology. - : SPRINGER. - 0340-7594 .- 1432-1351. ; 203:1, s. 15-22
-
Journal article (peer-reviewed)abstract
- While color vision and spatial resolution have been studied in many bird species, less is known about the temporal aspects of bird vision. High temporal resolution has been described in three species of passerines but it is unknown whether this is specific to passerines, to small actively flying birds, to insectivores or to birds living in bright habitats. Temporal resolution of vision is commonly tested by determining the flicker fusion frequency (FFF), at which the eye can no longer distinguish a flickering light from a constant light of equal intensity at different luminances. Using a food reward, we trained the birds to discriminate a constant light from a flickering light, at four different luminances between 750 and 7500 cd/m(2). The highest FFF found in one bird at 3500 cd/m(2) was 93 Hz. Three birds had higher FFF (82 Hz) at 7500 cd/m(2) than at 3500 cd/m(2). Six human subjects had lower FFF than the birds at 1500 but similar FFF at 750 cd/m(2). These results indicate that high temporal resolution is not a common trait for all small and active birds living in bright light habitats. Whether it is typical for passerines or for insectivorous birds remains to be tested.
|
|
| 3. |
- Boström, Jannika E., et al.
(author)
-
Ultra-Rapid Vision in Birds
- 2016
-
In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:3
-
Journal article (peer-reviewed)abstract
- Flying animals need to accurately detect, identify and track fast-moving objects and these behavioral requirements are likely to strongly select for abilities to resolve visual detail in time. However, evidence of highly elevated temporal acuity relative to non-flying animals has so far been confined to insects while it has been missing in birds. With behavioral experiments on three wild passerine species, blue tits, collared and pied flycatchers, we demonstrate temporal acuities of vision far exceeding predictions based on the sizes and metabolic rates of these birds. This implies a history of strong natural selection on temporal resolution. These birds can resolve alternating light-dark cycles at up to 145 Hz (average: 129, 127 and 137, respectively), which is ca. 50 Hz over the highest frequency shown in any other vertebrate. We argue that rapid vision should confer a selective advantage in many bird species that are ecologically similar to the three species examined in our study. Thus, rapid vision may be a more typical avian trait than the famously sharp vision found in birds of prey.
|
|
| 4. |
- de Jong, Johnny, et al.
(author)
-
Aktivitet av fladdermöss och insekter vid ett vindkraftverk
- 2019
-
Reports (other academic/artistic)abstract
- Det är väl dokumenterat att fladdermöss kan kollidera med vindkraftverk och det är viktigt att kartlägga de bakomliggande faktorerna för att minska risken för kollisioner. Det finns ett antal hypoteser som kan förklara varför fladdermöss kan förekomma vid vindkraftverkens rotorblad. En av dessa, som testas i den här studien, är att vindkraftverken attraherar insekter, och att fladdermössen nyttjar denna resurs för födosök. För att testa hypotesen placerades en insektsfälla vid nacellen på ett vindkraftverk i Småland, tillsammans med en mikrofon som registrerar fladdermusljud. Insektsfällan var en sugfälla som endast fångade insekter under natten, och utan att attrahera insekterna. Fångst av insekter och registrering av fladdermusljud gjordes under perioden 28 juni till 3 november, 2017. Samtidigt registrerades väderleksvariabler som temperatur, vindhastighet, vindriktning och nederbörd. Registrering av fladdermöss gjordes även under perioden 1 juli till 31 oktober 2018.Resultatet visar att det finns en korrelation mellan fladdermusaktiviteten och insektsabundansen. Det finns också signifikanta korrelationer mellan fladdermusaktivitet, temperatur och vindhastighet, liksom mellan insektsabundans och vindhastighet. Den negativa korrelationen mellan antal insekter och vindhastighet var ganska stark. Övriga korrelationer är dock ganska svaga och variationen var stor både när det gäller fladdermusaktivitet och insektsabundans. Sambanden mellan fladdermusaktivitet och väderlek tycks inte vara linjära. Fladdermusaktiviteten minskar när temperaturen sjunker under 10 grader och när vindhastigheten är större än 12 m/s. Vi kan också konstatera att det inte fanns någon korrelation mellan fladdermusaktiviteten på marken och aktiviteten uppe vid nacellen. Olika fladdermustaxa hade sin maximala aktivitet vid nacellen under olika tidpunkter, men med ett visst överlapp.Resultatet från studien ger stöd åt hypotesen att fladdermössen förekommer vid nacellen av vindkraftverken för födosök, men eftersom sambandet är så svagt, och variationen så stor ligger det nära till hands att anta att det finns fler faktorer inblandade, alternativt att fladdermössen är ganska dåliga på att prediktera insektsförekomsten. Ett sätt att minska dödligheten för fladdermöss i ett konfliktområde skulle kunna vara att minska vindkraftverkens attraktion av insekter (ljud, färg, belysning mm). Ett annat sätt kan vara stoppreglering under vissa väderbetingelser, och under vissa tidsperioder. Om man väljer stoppreglering blir det viktigt att så bra som möjligt ringa in under vilka förutsättningar vindkraftverken bör stå stilla. Vår bedömning är att variationen när det gäller fladdermusförekomst och dess respons på väderfaktorer kan vara ganska stor i olika geografiska regioner och det är därför viktigt att upprepa den här typen av försök på flera platser.
|
|
| 5. |
- Harris, Rebecca B., et al.
(author)
-
Discordance between genomic divergence and phenotypic variation in a rapidly evolving avian genus (Motacilla)
- 2018
-
In: Molecular Phylogenetics and Evolution. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 1055-7903 .- 1095-9513. ; 120, s. 183-195
-
Journal article (peer-reviewed)abstract
- Generally, genotypes and phenotypes are expected to be spatially congruent; however, in widespread species complexes with few barriers to dispersal, multiple contact zones, and limited reproductive isolation, discordance between phenotypes and phylogeographic groups is more probable. Wagtails (Motacilla) are a genus of birds with striking plumage pattern variation across the Old World. Up to 13 subspecies are recognized within a single species, yet previous studies using mitochondrial DNA have supported polyphyletic phylogeographic groups that are inconsistent with subspecies plumage characteristics. In this study, we investigate the link between phenotypes and genotype by taking a phylogenetic approach. We use genome-wide SNPs, nuclear introns, and mitochondrial DNA to estimate population structure, isolation by distance, and species relationships. Together, our genetic sampling includes complete species-level sampling and comprehensive coverage of the three most phenotypically diverse Palearctic species. Our study provides strong evidence for species-level patterns of differentiation, however population-level differentiation is less pronounced. SNPs provide a robust estimate of species-level relationships, which are mostly corroborated by a combined analysis of mtDNA and nuclear introns (the first time-calibrated species tree for the genus). However, the mtDNA tree is strongly incongruent and is considered to misrepresent the species phylogeny. The extant wagtail lineages originated during the Pliocene and the Eurasian lineage underwent rapid diversification during the Pleistocene. Three of four widespread Eurasian species exhibit an east-west divide that contradicts both subspecies taxonomy and phenotypic variation. Indeed, SNPs fail to distinguish between phenotypically distinct subspecies within the M. alba and M. flava complexes, and instead support geographical regions, each of which is home to two or more different looking subspecies. This is a major step towards our understanding of wagtail phylogeny compared to previous analyses of fewer species and considerably less sequence data.
|
|
| 6. |
- Håstad, Olle, et al.
(author)
-
A vision physiological estimation of ultraviolet window marking visibility to birds
- 2014
-
In: PeerJ. - : PeerJ. - 2167-8359. ; 2, s. e621-
-
Journal article (peer-reviewed)abstract
- Billions of birds are estimated to be killed in window collisions every year, worldwide. A popular solution to this problem may lie in marking the glass with ultraviolet reflective or absorbing patterns, which the birds, but not humans, would see. Elegant as this remedy may seem at first glance, few of its proponents have taken into consideration how stark the contrasts between ultraviolet and human visible light reflections or transmissions must be to be visible to a bird under natural conditions. Complicating matters is that diurnal birds differ strongly in how their photoreceptors absorb ultraviolet and to a lesser degree blue light. We have used a physiological model of avian colour vision to estimate the chromatic contrasts of ultraviolet markings against a natural scene reflected and transmitted by ordinary window glass. Ultraviolets markings may be clearly visible under a range of lighting conditions, but only to birds with a UVS type of ultraviolet vision, such as many passerines. To bird species with the common VS type of vision, ultraviolet markings should only be visible if they produce almost perfect ultraviolet contrasts and are viewed against a scene with low chromatic variation but high ultraviolet content.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Håstad, Olle, 1971-, et al.
(author)
-
Ultraviolet photopigment sensitivity and ocular media transmittance in gulls, with an evolutionary perspective
- 2009
-
In: Journal of Comparative Physiology A. Sensory, neural, and behavioral physiology. - : Springer Science and Business Media LLC. - 0340-7594 .- 1432-1351. ; 195:6, s. 585-590
-
Journal article (peer-reviewed)abstract
- Gulls (Laridae excluding Sternidae) appear to be the only shorebirds (Charadriiformes) that have a short wavelength sensitive type 1 (SWS1) cone pigment opsin tuned to ultraviolet (UV) instead of violet. However, the apparent UV-sensitivity has only been inferred indirectly, via the interpretation that the presence of cysteine at the key amino acid position 90 in the SWS1 opsin confers UV sensitivity. Unless the cornea and the lens efficiently transmit UV to the retina, gulls might in effect be similar to violet-sensitive birds in spectral sensitivity even if they have an ultraviolet sensitive (UVS) SWS1 visual pigment. We report that the spectral transmission of the cornea and lens of great black-backed Larus marinus and herring gulls L. argentatus allow UV-sensitivity, having a λ value, 344 nm, similar to the ocular media of UV sensitive birds. By molecular sequencing of the second α-helical transmembrane region of the SWS1 opsin gene we could also infer that 15 herring gulls and 16 yellow-legged gulls L. michahellis, all base-pair identical, are genetically UV-sensitive.
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Li, Xinlei, et al.
(author)
-
Shaped by uneven Pleistocene climate: mitochondrial phylogeographic pattern and population history of White Wagtail Motacilla alba (Aves: Passeriformes).
- 2016
-
In: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 47, s. 263-274
-
Journal article (peer-reviewed)abstract
- We studied the phylogeography and population history of the white wagtail Motacilla alba, which has a vast breeding range, covering areas with different Pleistocene climatic histories. The mitochondrial NADH dehydrogenase subunit II gene (ND2) and Control Region (CR) were analyzed for 273 individuals from 45 localities. Our data comprised all nine subspecies of white wagtail. Four primary clades were inferred (M, N, SW and SE), with indications of M. grandis being nested within M. alba. The oldest split was between two haplotypes from the endemic Moroccan M. a. subpersonata (clade M) and the others, at 0.63–0.96 Mya; other divergences were at 0.31–0.38 Mya. The entire differentiation falls within the part of the Pleistocene characterized by Milankovitch cycles of large amplitudes and durations. Clade N was distributed across the northern Palearctic; clade SW in southwestern Asia plus the British Isles and was predicted by Ecological niche models (ENMs) to occur also in central and south Europe; and clade SE was distributed in central and east Asia. e deep divergence within M. a. subpersonata may reflect retention of ancestral haplotypes. Regional differences in historical climates have had different impacts on different populations: clade N expanded after the last glacial maximum (LGM), whereas milder Pleistocene climate of east Asia allowed clade SE a longer expansion time (since MIS 5); clade SW expanded over a similarly long time as clade SE, which is untypical for European species. ENMs supported these conclusions in that the northern part of the Eurasian continent was unsuitable during the LGM, whereas southern parts remained suitable. e recent divergences and poor structure in the mitochondrial tree contrasts strongly with the pronounced, well defined phenotypical differentiation, indicating extremely fast plumage divergence.
|
|
| 14. |
- Lisney, Thomas J., et al.
(author)
-
Behavioural assessment of flicker fusion frequency in chicken Gallus gallus domesticus
- 2011
-
In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 51:12, s. 1324-1332
-
Journal article (peer-reviewed)abstract
- To interact with its visual environment, an organism needs to perceive objects in both space and time. High temporal resolution is hence important to the fitness of diurnally active animals, not least highly active aerial species such as birds. However, temporal resolution, as assessed by flicker fusion frequency (FFF; the stimulus frequency at which a flickering light stimulus can no longer be resolved and appears continuous) or critical flicker fusion frequency (CFF; the highest flicker fusion frequency at any light intensity) has rarely been assessed in birds. In order to further our understanding of temporal resolution as a function of light intensity in birds we used behavioural experiments with domestic chickens (Gallus gallus domesticus) from an old game breed 'Gammalsvensk dvarghona' (which is morphologically and behaviourally similar to the wildtype ancestor, the red jungle fowl, G. gallus), to generate an 'Intensity/FFF curve' (I/FFF curve) across full spectrum light intensities ranging from 0.2 to 2812 cd m(-2). The I/FFF curve is double-branched, resembling that of other chordates with a duplex retina of both rods and cones. Assuming that the branches represent rod and cone mediated responses respectively, the break point between them places the transition between scotopic and photopic vision at between 0.8 and 1.9 cd m(-2). Average FFF ranged from 19.8 Hz at the lowest light intensity to a CFF 87.0 Hz at 1375 cd m(-2). FFF dropped slightly at the highest light intensity. There was some individual variation with certain birds displaying CFFs of 90-100 Hz. The FFF values demonstrated by this non-selected breed appear to be considerably higher than other behaviourally derived FFF values for similar stimuli reported for white and brown commercial laying hens, indicating that the domestication process might have influenced temporal resolution in chicken.
|
|
| 15. |
- Lisney, Thomas J., et al.
(author)
-
Using electroretinograms to assess flicker fusion frequency in domestic hens Gallus gallus domesticus
- 2012
-
In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 62, s. 125-133
-
Journal article (peer-reviewed)abstract
- The assessment of flicker fusion frequency (FFF), the stimulus frequency at which a flickering light stimulus can no longer be resolved and appears continuous, and critical flicker fusion frequency (CFF; the highest frequency at any light intensity that an observer can resolve flicker) are useful methods for comparing temporal resolution capabilities between animals. Behavioural experiments have found that average CFFs in domestic chickens (Gallus gallus domesticus) are in the range of ca. 75-87 Hz, measured in response to full spectrum (i.e. white light plus UV) stimuli. In order to examine whether the chicken retina is able to detect flicker at higher frequencies, we used electroretinograms (ERGs) to assess FFF/CFF in adult hens from two commercial genotypes, Lohmann Selected Leghorns (LSLs) and Lohmann Browns (LBs). ERGs were recorded in response to flickering light at ten full spectrum light intensities ranging from 0.7 to 2740 cd m(-2). Two methods were used to determine FFF/CFF from the ERG recordings and these methods yielded very similar results, with average FFF ranging from ca. 20 Hz at 0.7 cd m(-2) to an average CFF of ca. 105 Hz at 2740 cd m(-2). In some individuals, CFFs of 118-119 Hz were recorded. The Intensity/FFF (I/FFF) curves are double-branched with a break point representing the rod-cone transition occurring between 2.5 and 5.9 cd m(-2). No significant differences in the I/FFF curves were found between the two genotypes. At stimulus light intensities >250 cd m(-2), the ERG-derived FFF and CFF values are all higher than those from behavioural studies using the same stimuli. Although hens do not appear to be able to consciously perceive flicker above approximately 90 Hz, the finding that the ERG responses are able to remain in phase with light flickering at frequencies >100 Hz means that the retinae of domestic poultry housed in artificial light conditions may be able to resolve flicker from fluorescent lamps. As range of detrimental effects have been reported in humans as a result of exposure to such "invisible flicker", the possibility exists that flicker from fluorescent lamps also acts as stressor in domesticated birds.
|
|
| 16. |
- Marzal, Julia Carolina Segami, et al.
(author)
-
Cryptic female Strawberry poison frogs experience elevated predation risk when associating with an aposematic partner
- 2017
-
In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:2, s. 744-750
-
Journal article (peer-reviewed)abstract
- Population divergence in sexual signals may lead to speciation through prezygotic isolation. Sexual signals can change solely due to variation in the level of natural selection acting against conspicuousness. However, directional mate choice (i.e., favoring conspicuousness) across different environments may lead to gene flow between populations, thereby delaying or even preventing the evolution of reproductive barriers and speciation. In this study, we test whether natural selection through predation upon mate-choosing females can favor corresponding changes in mate preferences. Our study system, Oophaga pumilio, is an extremely color polymorphic neotropical frog with two distinctive antipredator strategies: aposematism and crypsis. The conspicuous coloration and calling behavior of aposematic males may attract both cryptic and aposematic females, but predation may select against cryptic females choosing aposematic males. We used an experimental approach where domestic fowl were encouraged to find digitized images of cryptic frogs at different distances from aposematic partners. We found that the estimated survival time of a cryptic frog was reduced when associating with an aposematic partner. Hence, predation may act as a direct selective force on female choice, favoring evolution of color assortative mating that, in turn, may strengthen the divergence in coloration that natural selection has generated.
|
|
| 17. |
- Mege, Pascal, et al.
(author)
-
Partial Opsin Sequences Suggest UV-Sensitive Vision is Widespread in Caudata
- 2016
-
In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 43:1, s. 109-118
-
Research review (peer-reviewed)abstract
- Ultraviolet (UV) vision exists in several animal groups. Intuitively, one would expect this trait to be favoured in species living in bright environments, where UV light is the most present. However, UV sensitivity, as deduced from sequences of UV photoreceptors and/or ocular media transmittance, is also present in nocturnal species, raising questions about the selective pressure maintaining this perceptual ability. Amphibians are among the most nocturnal vertebrates but their visual ecology remains poorly understood relative to other groups. Perhaps because many of these species breed in environments that filter out a large part of UV radiation, physiological and behavioural studies of UV sensitivity in this group are scarce. We investigated the extent of UV vision in Caudata, the order of amphibians with the most nocturnal habits. We could recover sequences of the UV sensitive SWS1 opsin in 40 out of 58 species, belonging to 6 families. In all of these species, the evidence suggests the presence of functional SWS1 opsins under purifying selection, potentially allowing UV vision. Interestingly, most species whose opsin genes failed to amplify exhibited particular ecological features that could drive the loss of UV vision. This likely wide distribution of functional UV photoreceptors in Caudata sheds a new light on the visual ecology of amphibians and questions the function of UV vision in nocturnal animal species.
|
|
| 18. |
- Outomuro, David, et al.
(author)
-
The price of looking sexy : visual ecology of a three-level predator–prey system
- 2017
-
In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 31:3, s. 707-718
-
Journal article (peer-reviewed)abstract
- Colour signals and colour vision play a pivotal role in intraspecific communication and predator-prey interactions. However, the costs of expressing conspicuous sexual signals at multiple trophic levels have been largely overlooked. Sexual signals can also experience character displacement in sympatric populations of closely related species, leading to potential changes in conspicuousness. We here investigate a bird-damselfly-fruit fly predator-prey system, where two closely related damselfly species have conspicuous, sexually selected wing coloration. The damselflies can occur in sympatry and allopatry, and reproductive character displacement in the coloration size has been previously reported. We quantify the damselfly wing reflectance from replicated sympatric and allopatric populations, and use receptor noise models to investigate the visual discriminability of the wing coloration for the bird, damselfly and fly vision systems, against natural backgrounds. We perform electroretinograms to study damselfly eye sensitivity. We also estimate damselfly predation risk in natural populations. We find that the chromatic component of wing coloration makes males highly discriminable to the predator, but not to the prey. However, female wing coloration is predominantly cryptic for the predator and prey, and interestingly, also for male damselflies. A female being cryptic to conspecifics likely reduces male harassment. The estimates of predation risk partially support the discriminability results. We also show that there is no difference in colour vision sensitivity between the two damselfly species and sexes, and no difference in wing coloration or its discriminability between sympatric and allopatric populations. Our results suggest that sexually selected traits can be antagonistically selected by predators and prey and that this antagonistic selection can be sex-dependent: males are paying a large cost in terms of conspicuousness, while females remain mostly cryptic. Our study thus emphasizes the need for investigating visual communication at multitrophic levels since the degree of colour discriminability can differ between predators, prey and the focal species.
|
|
| 19. |
- Qvarnström, Anna, et al.
(author)
-
COARSE DARK PATTERNING FUNCTIONALLY CONSTRAINS ADAPTIVE SHIFTS FROM APOSEMATISM TO CRYPSIS IN STRAWBERRY POISON FROGS
- 2014
-
In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 68:10, s. 2793-2803
-
Journal article (peer-reviewed)abstract
- Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of strawberry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse patterning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represents a transient evolutionary state toward aposematism. Hence, a gain of either bright color or coarse patterning leads to conspicuousness, but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling aposematism by conspicuous color should be less likely to face an evolutionary dead end and more likely to radiate than populations with both conspicuous color and coarse patterning.
|
|
| 20. |
|
|
| 21. |
- Riyahi, Sepand, et al.
(author)
-
No association between the melanocortin-1 receptor (MC1R) and black belly stripe size variation in the Great Tit Parus major
- 2015
-
In: Bird Study. - : Informa UK Limited. - 0006-3657 .- 1944-6705. ; 62:1, s. 150-152
-
Journal article (peer-reviewed)abstract
- Capsule The Great Tit Parus major displays a black melanin breast patch stripe (black tie or black belly stripe) which shows great variation and its size correlates with male breeding success, survival and dominance. We investigated for associations between the melanocortin-1 receptor (MC1R) polymorphism, which has an important function in melanin colouration, and the size of the black belly stripe but were unable to detect any polymorphism in this gene. Variation in the size of the melanin-based black belly stripe may therefore be regulated through genetic variation at other genes or via modification of the gene expression inside the melanocortin system and melanogenesis.
|
|
| 22. |
- Rubene, Diana, et al.
(author)
-
The presence of UV wavelengths improves the temporal resolution of the avian visual system
- 2010
-
In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213:19, s. 3357-3363
-
Journal article (peer-reviewed)abstract
- The ability to perceive rapid movement is an essential adaptation in birds, which are involved in rapid flight, pursuing prey and escaping predators. Nevertheless, the temporal resolution of the avian visual systems has been less well explored than spectral sensitivity. There are indications that birds are superior to humans in their ability to detect movement, as suggested by higher critical flicker frequencies (CFFs). It has also been implied, but not properly tested, that properties of CFF, as a function of light intensity, are affected by the spectral composition of light. This study measured CFF in the chicken, Gallus gallus L., using four different light stimuli - white, full-spectrum (white with addition of UV), yellow (590 nm) and UV (400 nm) - and four light intensity levels, adjusted to relative cone sensitivity. The results showed significantly higher CFF values for full-spectrum compared with white light, as well as a steeper rate of increase with intensity. The presence of UV wavelengths, previously demonstrated to affect mate choice and foraging, appears to be important also for detection of rapid movement. The yellow and UV light stimuli yielded rather similar CFFs, indicating no special role for the double cone in flicker detection.
|
|
| 23. |
|
|
| 24. |
- Rundle, H.D., et al.
(author)
-
An experimental test for indirect benefits in Drosophila melanogaster
- 2007
-
In: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 7, s. 36-
-
Journal article (peer-reviewed)abstract
- Background. Despite much empirical attention, tests for indirect benefits of mate choice have rarely considered the major components of sexual and nonsexual offspring fitness relevant to a population. Here we use a novel experimental design to test for the existence of any indirect benefits in a laboratory adapted population of D. melanogaster. Our experiment compared the fitness (mating success, longevity, and productivity) of individuals possessing genomes that derived two generations previously from males that were either entirely successful (studs) or wholly unsuccessful (duds) at achieving mates in three subsequent rounds of mating trials. Results. Males from the stud treatment were 30% more successful on average at securing mates than males from the dud treatment. In contrast, we found no difference between treatments in measures of productivity or of longevity when measured in a mixed-sex environment. In the absence of females, however, males in the stud treatment outlived males in the dud treatment. Conclusion. Our results suggest that mating with successful males in this population provides an indirect benefit to females and that, at least in this environment, the benefit arises primarily through the production of more attractive male offspring. However, it is unclear whether this represents solely a traditional sexy sons benefit or whether there is an additional good genes component (with male offspring simply allocating their surplus condition to traits that enhance their mating success). The lack of any detectable differences in female fitness between the two treatments suggests the former, although the longevity advantage of males in the stud treatment when females were absent is consistent with the latter. Determining the effect of this indirect benefit on the evolution of female mate preferences (or resistance) will require comparable data on the direct costs of mating with various males, and an understanding of how these costs and benefits integrate across generations and vary among environments.
|
|
| 25. |
- Seddon, Nathalie, et al.
(author)
-
Human Vision Can Provide a Valid Proxy for Avian Perception of Sexual Dichromatism
- 2010
-
In: The AUK. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 127:2, s. 283-292
-
Journal article (peer-reviewed)abstract
- The study of sexual dichromatism has played an important role in the development and testing of evolutionary theory. However, previous work has often relied on human vision to assess plumage color and contrast, an approach challenged by the finding that dichromatism is often visible to birds but invisible to humans. We explicitly tested whether the use of human vision undermines previous comparative analyses in antbirds (Thamnophilidae). Focusing on a sample of 71 species, we used (1) molecular sequencing of the SWS1 opsin gene to assess spectral sensitivity and (2) spectrophotometry and color discrimination models to compare human and avian perception of dichromatism. We show that antbirds, like the majority of avian families studied to date, are violet-sensitive (VS) rather than ultraviolet-sensitive (UVS). We also demonstrate that species perceived as monochromatic by humans may look dichromatic to antbirds, but that human and avian perceptions of dichromatism are nonetheless positively correlated. To assess whether this relationship validates the assumptions of published comparative analyses, we re-ran the analyses using avian-perceived dichromatism; the results remained qualitatively unchanged. Although it is clear that the use of spectrophotometry and visual models can improve measurements of plumage coloration, we conclude that scores generated from human perception provide a meaningful estimate of sexual dichromatism for the purposes of comparative analyses, at least in antbirds. Furthermore, our results suggest that discrepancies between human and avian perceptions of sexual color differences may be relatively minor in avian families with VS visual systems. Received 7 July 2009, accepted 16 October 2009.
|
|
