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1.
Mennill Daniel J. Doucet Stéphanie M. Montgomerie Robert Ratcliffe Laurene M. 《Behavioral ecology and sociobiology》2003,53(6):350-357
Sexual dichromatism and phenotypic variation in elaborate male traits are common products of sexual selection. The spectral properties of carotenoid and structurally-based plumage colors and the patch sizes of melanin-based plumage colors have received considerable attention as sexual signals in birds. However, the importance of variation in achromatic plumage colors (white, gray and black) remains virtually unexplored, despite their widespread occurrence. We investigated a potential signal function of the achromatic black and white plumage of black-capped chickadees (Poecile atricapilla). We captured and color-banded 178 free-living chickadees and assessed winter flock dominance hierarchies by tabulating pairwise interactions at feeders. We recaptured 73 of these birds and measured plumage coloration for six body regions using a reflectance spectrometer and the area of melanin-based plumage patches from standardized photographs. We found extensive individual variation in chickadee plumage traits and considerable sexual dichromatism. Male black-capped chickadees have significantly brighter white plumage than females, larger black patches, and greater plumage contrast between adjacent white and black plumage regions. We also found rank differences in the plumage reflectance of males; high-ranking males, who are preferred by females as both social and extra-pair partners, exhibit significantly darker black plumage and grow their feathers more rapidly than low-ranking males. This variation among individuals reveals a potential signal function for achromatic plumage coloration in birds. 相似文献
2.
Joël Meunier Susana Figueiredo Pinto Reto Burri Alexandre Roulin 《Behavioral ecology and sociobiology》2011,65(4):559-567
Although melanin is the most common pigment in animal integuments, the adaptive function of variation in melanin-based coloration
remains poorly understood. The individual fitness returns associated with melanin pigments can be variable across species
as these pigments can have physical and biological protective properties and genes involved in melanogenesis may vary in the
intensity of pleiotropic effects. Moreover, dark and pale coloration can also enhance camouflage in alternative habitats and
melanin-based coloration can be involved in social interactions. We investigated whether darker or paler individuals achieve
a higher fitness in birds, a taxon wherein associations between melanin-based coloration and fitness parameters have been
studied in a large number of species. A meta-analysis showed that the degree of melanin-based coloration was not significantly
associated with laying date, clutch size, brood size, and survival across 26 species. Similar results were found when restricting
the analyses to non-sexually dimorphic birds, colour polymorphic and monomorphic species, in passerines and non-passerines
and in species for which inter-individual variation in melanism is due to colour intensity. However, eumelanic coloration
was positively associated with clutch and brood size in sexually dimorphic species and those that vary in the size of black
patches, respectively. Given that greater extent of melanin-based coloration was positively associated with reproductive parameters
and survival in some species but negatively in other species, we conclude that in birds the sign and magnitude of selection
exerted on melanin-based coloration is species- or trait-specific. 相似文献
3.
Status signals are traits that advertise an individual’s competitive abilities to conspecifics during aggressive disputes.
Most studies of status signals in birds have focussed on melanin-based plumage signals, but recent research shows that carotenoid-based
signals may also play a role in aggressive signaling. We assessed the relative importance of melanin- and carotenoid-based
plumage patches as agonistic signals in a small passerine, the golden whistler (Pachycephala pectoralis). Display signals in male golden whistlers include an unpigmented white throat patch, a carotenoid-based yellow breast and
nape band, and a melanin-based black chin-stripe. We found that only the white throat patch was correlated with contest-related
attributes. Males possessing large throat patches defended larger territories and commenced breeding earlier. When caged males
with either experimentally reduced, or unmanipulated throat patches were presented to conspecifics, those with experimentally
reduced patches attracted less aggression from male subjects. Focal males also responded faster to caged males with throat
patches similar in size to their own, suggesting that they may assess relative throat patch size before engaging in aggressive
encounters. Females did not discriminate between “reduced” or “control” treatments. Our data strongly suggest that only the
unpigmented throat patch functions as a status signal. As this signal is unlikely to have significant development costs, honesty
may be maintained through social costs. 相似文献
4.
José P. Veiga 《Behavioral ecology and sociobiology》1996,39(5):345-352
In many bird species the cryptic winter plumage is due to the presence of light feather tips that conceal conspicuous colorations.
The gradual abrasion of these tips that makes sexual traits visible has been interpreted as a strategy to improve mating success
(here referred as the permanent exhibition hypothesis). However, under some circumstances, the maintenance of a full plumage
that facultatively enables the bird to exhibit or cover aggression-inducing traits has proved to be advantageous (the coverable
badge hypothesis). In a population of house sparrows where black throat patches (here called badges) are used in intrasexual
competition, the degree of abrasion of dull feather tips that conceal bright colour early in the breeding season correlated
neither with badge size nor with traits indicating morphology and body condition. These results are only in accordance with
predictions of the coverable badge hypothesis. In 1992 experimental clipping of badge feather tips, which forced permanent
exposure of badges, negatively affected birds with the largest badges in terms of nest acquisition, but an opposite trend
was indicated for birds with the smallest badges. In 1993, when more novel birds in the study area were competing for nesting
sites than in 1992, only badge size, but not the experimental manipulation, affected nesting success. These results suggest
that the loss of the ability to conceal badges was disadvantageous, and more so if most competing individuals had already
been resident in the colony in previous years and the larger their badges were. There is a striking contrast between the results
reported for this study population, where badges mainly signal fighting ability, and those reported for another house sparrow
population, where badges are mainly used in mate choice. In this last population, tip abrasion is advantageous for dominant
individuals showing the largest badges. This suggests that the trade-off between conserving versus wearing off the feathers
that conceal ornaments could have different optimal resolutions depending on the relative importance of inter and intrasexual
selection on indicator traits.
Received: 29 September 1995/Accepted after revision: 14 July 1996 相似文献
5.
Veronika Bókony László Zsolt Garamszegi Katharina Hirschenhauser András Liker 《Behavioral ecology and sociobiology》2008,62(8):1229-1238
Despite the functional significance of melanin-based plumage coloration in social and sexual signaling, the mechanisms controlling
its information content are poorly understood. The T-regulation hypothesis proposes that melanin ornaments signal competitive
abilities via the effects of testosterone (T) mediating both melanization and sexual/aggressive behaviors. Using the phylogenetic
comparative approach, we tested whether frontal black melanization is associated with elevated T around the time of breeding
plumage development across all bird species with available T-data. We found a context-dependent relationship between melanization
and T, varying with the type of ornamentation (patchy or full-black) and with the presumed taxonomic distribution of the hormonal
control of plumage dichromatism. Within two taxa in which male plumage development is assumed androgen-dependent (Charadriiformes,
Corvida), evolutionary increases in male melanization, and melanin dichromatism correlated with increases in T in most analyses
but not within the basal lineage (ratites, Galloanseriformes) with androgen-independent male plumage. Among Passeroidea with
presumably genetically or luteinizing-hormone-based male plumage, melanization and its dichromatism correlated with T only
in species with <100% frontal melanization. These results were robust as we controlled for several confounding variables such
as mating and parental behaviors. This study is the first to test and support the T-regulation hypothesis interspecifically,
suggesting that among-species differences in melanization may have evolved in response to differences in circulating T in
certain avian taxa. Our results imply that the extent of black ornamentation may serve as an honest indicator of male competitiveness
in those species that evolved an appropriate hormonal basis (T dependence) for color production.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
The handicap principle suggests that ornamental traits that function as honest signals in mate selection must be costly to be effective. We evaluated in the sexually monochromatic yellow-eyed penguin (Megadyptes antipodes) whether the carotenoid-derived plumage and eye coloration predicts parental quality and whether males and females within pairs mate assortatively in relation to these carotenoid-derived ornaments. In addition, we investigated whether age or body condition was related to the coloration of the ornamental traits. In yellow-eyed penguins, parental quality of males and females was predicted by eye and head plumage coloration. Even when we controlled for gender- and age-specific differences, eye and head plumage coloration reflected honestly parental quality. Males and females mated assortatively in relation to these ornamental traits. While age influenced coloration of both the eye and head plumage, body condition was related only to the saturation of plumage coloration. These results provide evidence that the carotenoid-derived ornaments in yellow-eyed penguins reflect the parental abilities of birds and, therefore, may be costly signals. Potentially, female and male yellow-eyed penguins could use eye and plumage coloration as an indirect cue in assessing age and quality of individual birds during mate choice. This is only the second study to examine plumage coloration in relation to sexual selection in penguins, while conspicuous ornamental traits in other species of penguin beg the question whether they also play a role in sexual selection.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by C.R. Brown 相似文献
7.
Several experimental studies have shown that female birds use ornamental melanin and carotenoid plumage coloration as criteria
in mate choice. Whether females choose mates based on natural variation in structural coloration, however, has not been well
established. Male eastern bluebirds (Sialia sialis) display brilliant ultraviolet (UV)-blue plumage coloration on their head, back, wings, and tail, which is positively correlated
with condition, reproductive effort, and reproductive success. We experimentally tested the hypothesis that female eastern
bluebirds prefer as mates males that display brighter structural coloration by presenting breeding-condition females with
males of variable coloration. We conducted two types of mate-choice experiments. First, females chose between males whose
coloration was manipulated within the natural range of variation in the population; feathers were either brightened with violet
marker or dulled with black marker. Second, females chose between males with naturally dull or bright plumage coloration.
In both manipulated and unmanipulated coloration trials, female choice did not differ significantly from random with respect
to structural coloration. We found no support for the hypothesis that the UV–blue coloration of male eastern bluebirds functions
as a criterion in female mate choice. 相似文献
8.
The effects of preen oils and soiling on the UV–visible reflectance of carotenoid-pigmented feathers
Lorenzo Pérez-Rodríguez Francois Mougeot Gary R. Bortolotti 《Behavioral ecology and sociobiology》2011,65(7):1425-1435
Plumage coloration, particularly when carotenoid-based, is important in social signaling in birds. Although feather color
is a relatively stable trait, individuals may modify it with “cosmetic” substances such as preen oils. In addition, dirt accumulation
may influence plumage coloration and further affect signal perception by receivers. Here, we analyze the separate potential
effects of preen oils and soil accumulation on the reflectance properties of carotenoid-pigmented feathers across the visual
range of most bird species, which includes the ultraviolet (UV). Using the yellow portion of tail feathers of Bohemian waxwings
(Bombycilla garrulus), we performed two separate experiments where: (a) preen oils and/or soil were removed, or (b) preen oils (from black-billed
magpies Pica pica or eagle owls Bubo bubo) were added. Preen oil addition reduced brightness but increased UV hue and yellow chroma. UV chroma was reduced by the addition
of magpie (but not owl) preen oil. Soil accumulation had little effect on plumage reflectance in the UV range but significantly
reduced yellow chroma. According to models of avian vision, both of these effects are detectable by birds and biologically
meaningful when compared with natural variation between the sexes and age classes. We conclude that preen oil and soil accumulation
can significantly affect the UV–visible reflectance of carotenoid-based plumages. As such traits typically advertise individual
quality, preening and soiling have the potential to modify the information content of carotenoid-based plumage traits and
how these signals are perceived by receivers. 相似文献
9.
Delayed plumage maturation in Lazuli buntings: tests of the female mimicry and status signalling hypotheses 总被引:1,自引:0,他引:1
Vincent R. Muehter Erick Greene Laurene Ratcliffe 《Behavioral ecology and sociobiology》1997,41(4):281-290
The evolutionary importance of delayed plumage maturation (DPM) in passerines, the condition when more than 1 year is required
to achieve adult-like coloration, remains highly contentious. Adaptive hypotheses propose that aggression from after 2nd-year
(ASY) males or predation favors DPM in 2nd-year (SY) males, thereby increasing SY male survivorship or reproductive success.
However, each hypothesis suggests a distinct selective mechanism explaining “how” this is accomplished. Alternatively, DPM
may be a consequence of a nonadaptive molt constraint. We tested the female mimicry and status signalling hypotheses in territorial
ASY male lazuli buntings (Passerinaamoena) using three sets of model presentation experiments. The female mimicry hypothesis proposes that dull SY male plumage deceptively
mimics female plumage, and predicts that ASY males can not distinguish SY male from female plumage. The status signalling
hypothesis proposes that dull SY male plumage honestly signals low competitive threat, and predicts that ASY males respond
less aggressively to dull versus bright, ASY-like plumage. Contrary to the female mimicry hypothesis, ASY males distinguished
between SY male and female plumage, as they were aggressive to SY male models exclusively and attempted to copulate with female
models. Supporting the status signalling hypothesis, ASY males were significantly less aggressive to SY versus ASY male plumage.
While DPM may result from a physiological constraint on bright SY male plumage, our results support the idea that dull plumage
in an SY male's first breeding season may be maintained by selection to reduce aggression from ASY males, serving as a signal
of competitive status.
Received: 21 February 1997 / Accepted after revision: 16 June 1997 相似文献
10.
Joel W. McGlothlin Deborah L. Duffy Jessica L. Henry-Freeman Ellen D. Ketterson 《Behavioral ecology and sociobiology》2007,61(9):1391-1399
Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition
dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources.
White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment
nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined
the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce
replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers
grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather
growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger
in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together,
these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition
dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may
lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness. 相似文献
11.
Bridget J. Stutchbury 《Behavioral ecology and sociobiology》1992,31(1):27-33
Summary I tested the hypothesis that bright breeding plumage in territorial males acts as a badge of fighting ability or aggressive motivation to intimidate intruders. Territorial male purple martins (Progne subis) whose iridescent blue plumage was lightened to mimic the appearance of subadult males did not suffer an increase in intruder pressure or loss of territory compared with control males. Bright plumage color itself did not deter intruders and was not important for successful territory defense. Furthermore, a bright coloration of owners was not associated with an increased level of aggression toward intruders. Results from parallel studies on this species suggest that bright coloration is important in territory acquisition. The effectiveness of badges of fighting ability and aggressive motivation in territory defense is limited by whether intruders benefit from assessing these traits in owners. Differences in signaling systems between species are due in part to differences in floater tactics and the mode of territory acquisition. 相似文献
12.
The honesty of ornamental signals of quality is often argued to be enforced via costs associated with testosterone. It is
still poorly understood, however, how seasonal variation of testosterone within individuals is related to the timing and extent
of ornament development. Here, we studied inter- and intra-individual variability of plasma testosterone levels in a population
of 150 captive male house sparrows (Passer domesticus) through the course of a full year. We further analyzed the relationship between plasma testosterone levels and two sexually
dimorphic ornaments: badge size and bill coloration. Also, because of a known negative relation between molt and circulating
testosterone levels, we analyzed the relationship between ornamentation and molt status during the fall. We found that testosterone
levels increased towards the breeding season and decreased before the onset of annual molt. However, within individuals, relative
testosterone titers demonstrated low repeatability between seasons. Plasma testosterone levels were not correlated with badge
size in any season but were correlated strongly with bill coloration during all periods, except the breeding season when variation
in bill color was low. Finally, we found that bill coloration strongly correlated with molt status during fall. Our results
indicate that bill coloration, not badge size, is the best ornamental indicator of a “running average” of male testosterone
in house sparrows and therefore the best potential indicator of qualities and/or behavioral strategies associated with testosterone. 相似文献
13.
Juan A. Amat Miguel A. Rendón Juan Garrido-Fernández Araceli Garrido Manuel Rendón-Martos Antonio Pérez-Gálvez 《Behavioral ecology and sociobiology》2011,65(4):665-673
It was long thought that the colour of bird feathers does not change after plumage moult. However, there is increasing evidence
that the colour of feathers may change due to abrasion, photochemical change and staining, either accidental or deliberate.
The coloration of plumage due to deliberate staining, i.e. with cosmetic purposes, may help individuals to communicate their
quality to conspecifics. The presence of carotenoids in preen oils has been previously only suggested, and here we confirm
for the first time its presence in such oils. Moreover, the carotenoids in the uropygial secretions were the same specific
pigments found in feathers. We show not only that the colour of feathers of greater flamingos Phoenicopterus roseus became more colourful due to the application of carotenoids from uropygial secretions over the plumage but also that the
feathers became more colourful with the quantity of pigments applied over them, thus providing evidence of cosmetic coloration.
Flamingos used uropygial secretions as cosmetic much more frequently during periods when they were displaying in groups than
during the rest of the year, suggesting that the primary function of cosmetic coloration is mate choice. Individuals with
more colourful plumage initiated nesting earlier. There was a correlation between plumage coloration before and after removal
of uropygial secretions from feathers’ surfaces, suggesting that the use of these pigmented secretions may function as a signal
amplifier by increasing the perceptibility of plumage colour, and hence of individual quality. As the cosmetic coloration
strengthens signal intensity by reinforcing base-plumage colour, its use may help to the understanding of selection for signal
efficacy by making interindividual differences more apparent. 相似文献
14.
We used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by
eastern bluebird (Sialia sialis) nestlings. Ultraviolet (UV)-blue structural coloration has been shown to be sexually selected in this species. Our experimental
design took advantage of the growth of UV-blue wing feathers in nestlings that are retained as part of the first nuptial plumage.
We cross-fostered nestlings to create enlarged and reduced broods with the purpose of manipulating parental feeding rates
and measured the effect on nestling growth and plumage coloration. Brood size influenced feeding rates to offspring, but the
effect varied with season. In general, male nestlings reared in reduced broods were fed more often, weighed more, and displayed
brighter structural plumage compared to nestlings reared in enlarged broods. Female nestlings appeared to experience less
adverse affects of brood enlargement, and we did not detect an effect of brood-size manipulation on the plumage coloration
of female nestlings. Measures of plumage coloration in both males and females, however, were correlated to hatching date and
nestling mass during feather development. These data provide empirical evidence that environmental quality can influence the
development of the blue structural coloration of feathers and that males may be more sensitive to environmental fluctuations
than females. 相似文献
15.
In socially monogamous species, extra-pair paternity may increase the reproductive success of highly ornamented males, mediating the evolution of sexual ornaments. However, ornaments may also attract social mates, and a tradeoff between extra-pair paternity (EPP) and within-pair paternity (WPP) may complicate mating strategies. Further, in many socially monogamous species, females are also ornamented, and the relationship between female ornamentation and patterns of EPP has been neglected. We investigated the patterns of genetic paternity with respect to carotenoid- and melanin-based pigmentation in yellow warblers (Setophaga petechia) of both sexes. We asked whether males face tradeoffs between EPP and WPP, how paternity patterns relate to carotenoid- versus melanin-based pigmentation, and whether less EPP occurs in broods when males and females are assortatively paired. Males faced a tradeoff between EPP and WPP. Moreover, non-additive relationships existed between paternity patterns and the two pigment types in both sexes. Males with high melanin coverage but dull carotenoid pigmentation achieved EPP but lost WPP, whereas males with high levels of both pigment types had high WPP but gained little EPP. A parallel pattern occurred in females. Warblers paired assortatively by pigmentation and EPP was less common in broods when the sexes were assortatively paired by carotenoid pigmentation. Results suggest that the most colorful birds obtain high quality social mates and advance reproductive success through WPP, show that correlations can arise between female ornamentation and patterns of EPP, and also uniquely suggest that social pairing patterns may influence extra-pair mating strategies. 相似文献
16.
Delayed plumage maturation in the orchard oriole (Icterus spurius): tests of winter adaptation hypotheses 总被引:1,自引:0,他引:1
David A. Enstrom 《Behavioral ecology and sociobiology》1992,30(1):35-42
Summary Explanations of delayed plumage maturation (DPM) in passerines have focused on potential breeding season advantages for non-definitive (subadult) plumage. In contrast, the molt constraint hypothesis (Rohwer and Butcher 1988) proposes that subadult plumage is a winter adaptation, increasing winter survivorship by decreasing intraspecific aggression (the winter status signaling hypothesis) or predation (the winter crypsis hypothesis). Under the molt constraint hypothesis, nondefinitive breeding plumage is non-adaptive, resulting from species-specific constraints on the number of feathers replaced during the pre-alternate (spring) molt. In studies conducted on an overwintering population of orchard orioles in Panama, I tested predictions of both the winter status signaling and molt constraint hypotheses. Contrary to predictions of winter status signaling, I found no evidence that subadult plumage reduces adult male aggression toward subadults. Agonistic encounters occurred at random with respect to plumage and the intensity of adult male/subadult male encounters was not lower than the intensity of encounters occurring within age classes. Contrary to the molt constraint hypothesis, I found no evidence that the number of feathers exchanged by subadults in their pre-alternate molt is the sole constraint on the development of subadult breeding plumage. The majority of feathers grown by molting subadult orioles during January and February were of non-definitive coloration. These results, together with results of earlier breeding season experiments which tested summer communication hypotheses for DPM in this species, suggest that subadult plumage in the orchard oriole may be non-adaptive and the result of constraints on plumage development. They also indicate, however, that the extent of the pre-alternate molt is not the sole source of that constraint. 相似文献
17.
Peter Korsten Oscar Vedder István Szentirmai Jan Komdeur 《Behavioral ecology and sociobiology》2007,61(12):1933-1943
Structurally based ultraviolet (UV)-reflective plumage parts can be important cues in mate choice. However, it remains largely
unknown if UV plumage variation can also function as a signal of social status during competitive interactions. In blue tits
(Cyanistes caeruleus), the UV-reflective crown plumage functions as a female mate choice cue that probably indicates male quality, as males with
higher UV reflectance have been shown to have better chances of over-winter survival. Possibly, the UV crown plumage acts
as a status signal in the competition over scarce food sources during winter. To test this idea, we related dominance of individuals
at an artificial food source during adverse winter conditions to spectrophotometric measurements of their crown plumage. However,
while controlling for the confounding effects of sex, age, and distance from territory, we found no significant effect of
crown UV reflectance on dominance. Consistent with this result, we also found no relation between crown UV reflectance and
over-winter survival. We conclude that the structurally based UV reflectance of the blue tit crown feathers plays little role
in competition between individuals during winter despite its importance as a cue in mate choice. 相似文献
18.
Zachary M. Laubach Daniel T. Blumstein L. Michael Romero Greg Sampson Johannes Foufopoulos 《Behavioral ecology and sociobiology》2013,67(3):481-492
Status badges, such as crown plumage, mediate intraspecific interactions. The reliability of crown morphology as a status badge in male mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) is uncertain. We examined morphological and physiological correlates of the proportion of crown that was white (“crown-white”) in 178 male mountain white-crowned sparrows during the 2008–2009 breeding seasons. Using a paired experimental design, we presented territory-holding males with white-enhanced and white-reduced decoys and recorded aggressive behaviors. To assess physiological constraints on signal bluffing, a subsample of birds was captured and released after manipulating natural crowns to simulate bluffed white-enhanced or white-reduced crowns; corticosterone concentrations were assayed from blood drawn upon recapture and after a restraint-induced stressor. We found a significant positive association between crown-white and a measure of body size—tarsus length—which is an established indicator of resource-holding potential. In the decoy challenge, males responded more aggressively toward white-enhanced than white-reduced decoys. In the hormone experiment, white-enhanced birds had higher baseline corticosterone levels, whereas white-reduced birds had similar concentrations to controls. Furthermore, white-enhanced birds had an attenuated restraint-induced corticosterone response, while white-reduced birds mounted a significantly larger increase in corticosterone than controls. Taken together, these findings indicate that crown-white is a reliable status badge of resource-holding potential in male mountain white-crowned sparrows during the breeding season. 相似文献
19.
A. Roulin J. Gasparini P. Bize M. Ritschard H. Richner 《Behavioral ecology and sociobiology》2008,62(4):507-519
One hypothesis for the maintenance of genetic variation states that alternative genotypes are adapted to different environmental
conditions (i.e., genotype-by-environment interaction G×E) that vary in space and time. Although G×E has been demonstrated
for morphological traits, little evidence has been given whether these G×E are associated with traits used as signal in mate
choice. In three wild bird species, we investigated whether the degree of melanin-based coloration, a heritable trait, covaries
with nestling growth rate in rich and poor environments. Variation in the degree of reddish-brown phaeomelanism is pronounced
in the barn owl (Tyto alba) and tawny owl (Strix aluco), and variation in black eumelanism in the barn owl and Alpine swift (Apus melba). Melanin-based coloration has been shown to be a criterion in mate choice in the barn owl. We cross-fostered hatchlings
to test whether nestlings sired by parents displaying melanin-based colorations to different extent exhibit alternative growth
trajectories when raised by foster parents in poor (experimentally enlarged broods) and rich (experimentally reduced broods)
environments. With respect to phaeomelanism, barn owl and tawny owl offspring sired by redder parents grew more rapidly in
body mass only in experimentally reduced broods. With respect to eumelanism, Alpine swift offspring of darker fathers grew
their wings more rapidly only in experimentally enlarged broods, a difference that was not detected in reduced broods. These
interactions between parental melanism and offspring growth rate indicate that individuals display substantial plasticity
in response to the rearing environment which is associated with the degree of melanism: at least with respect to nestling
growth, phaeomelanic and eumelanic individuals are best adapted to rich and poor environments, respectively. It now remains
to be investigated why eumelanism and phaeomelanism have a different signaling function and what the lifelong consequences
of these melanism-dependent allocation strategies are. This is important to fully appraise the role played by environmental
heterogeneity in maintaining variation in the degree of melanin-based coloration. 相似文献
20.
Eileen A. Kennedy Christine R. Lattin L. Michael Romero Donald C. Dearborn 《Behavioral ecology and sociobiology》2013,67(2):341-348
Colorful ornaments in birds are often sexually selected signals of quality, and variation in ornament expression may be mediated by physiological stress through the secretion of corticosterone. However, testing for links between ornamentation and corticosterone often requires sampling live animals, and such physiological measures may not be matched in the time span in which they were sampled (e.g., very dynamic plasma corticosterone vs. plumage coloration, which is relatively static). Here, we use museum specimens to test for a link between the color of a sexual ornament and feather corticosterone at the time of ornament formation. In red-winged blackbirds, Agelaius phoeniceus, carotenoid-based epaulets appear to be important in male–male social interactions, territory maintenance, and female choice. We measured reflectance spectra of adult male epaulets and plucked adjacent feathers for corticosterone analysis via radioimmunoassay. We controlled for differences in the number of mates, specimen age, and geography by selecting only males with one mate and only birds collected in Florida during a 3-year period. Epaulet hue and red chroma did not vary with feather corticosterone, but males whose epaulets scored high for mean brightness and red brightness had significantly lower corticosterone than males with low brightness scores. This correlation with brightness but not hue or chroma is consistent with an effect of corticosterone (CORT) on feather microstructure, with elevated CORT leading to lower reflectance of white light from the keratin matrix surrounding the carotenoid pigments. 相似文献