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30 results for “Colour difference”
Eggshell colour differences in a classic example of coevolved eggshell mimicry
<p>Avian brood parasitism is a model system for understanding coevolutionary arms races, and the great reed warbler (<em>Acrocephalus arundinaceus</em>, hereafter 'warbler') and its parasite the common cuckoo (<em>Cuculus canorus</em>, hereafter 'cuckoo') are prime examples of this coevolutionary struggle. Here, warblers select for egg colour mimicry by rejecting poorly matched cuckoo eggs. Contrary to long-held assumptions, recent work showed that warblers tend to reject lighter and browner eggs but tended to accept darker and bluer eggs rather than basing rejection decisions solely on perceived colour differences (i.e., the degree of mimicry). This counter-intuitive, colour-biased rejection behaviour would select for bluer and darker cuckoo eggs, but would only be adaptive if cuckoos were consistently lighter and browner than warbler eggs. Therefore, we tested whether warbler eggs were consistently bluer and darker than the cuckoo eggs. To do so, we re-analysed eggshell reflectance spectra of warblers and the cuckoos that parasitized them in the Czech Republic. As expected, we found that warbler eggs were significantly bluer and darker than the cuckoo eggs at the population level. Thus, we demonstrate imperfect mimicry in a long-coevolved cuckoo host-race and provide insights for exploring the coevolutionary interactions among hosts and their brood parasites.</p>
Рис. 3. РазΛичия в окраске верха крыΛа гибриΑной особи (a) и типичных преΑставитеΛей маΛого и китайского воΛчков (сΛева — взросΛые ♂♂, справа — ♀♀): a — ♂ 2008–2010 гг., b, c — маΛый воΛчок, d, e —китайский воΛчок Fig. 3. Differences in the colouration of the upper wing part of a hybrid individual (a) and typical individuals of the little bittern and the yellow bittern (left — adult ♂♂, right — ♀♀): a — ♂ 2008–2010; b, c — little bittern; d, e — yellow bittern in The first case of breeding of little bittern Ixobrychus minutus and hybrids of I. minutus with I. sinensis in the Russian Far East
Рис. 3. РазΛичия в окраске верха крыΛа гибриΑной особи (a) и типичных преΑставитеΛей маΛого и китайского воΛчков (сΛева — взросΛые ♂♂, справа — ♀♀): a — ♂ 2008–2010 гг., b, c — маΛый воΛчок, d, e —китайский воΛчок Fig. 3. Differences in the colouration of the upper wing part of a hybrid individual (a) and typical individuals of the little bittern and the yellow bittern (left — adult ♂♂, right — ♀♀): a — ♂ 2008–2010; b, c — little bittern; d, e — yellow bittern
Sanderlings (Calidris alba) of two different age classes at the moment of individual colour-marking at four non-breeding sites that were or were not observed during migration following the capture.
<p>The data file contains data of Sanderlings (<em>Calidris alba</em>) of two different age classes at the moment of capture and individual colour-marking at one of four wintering areas that were or were not observed during migration following the capture. Each individual is indicated with a unique number in column “BirdID”. The column “country” indicates which of the four wintering areas (as depicted in Fig. 1 in the manuscript), with GB indicating England, PT indicating Portugal, MR indicating Mauritania and GH indicating Ghana. The “age” of each bird was either juvenile (<1 year old) or adult (>1 year old). Whether an individual was observed during migration, i.e. at least 2 latitudinal degrees north of its average winter location between 15 March – 15 October, in the migration period following capture is indicated with a 0 (not observed) or 1 (observed) in the column “observed”. Further details can be found in the methods section in the manuscript.</p>
Рис. 26. Сравнение среΑних значений частоты изменчивости эΛементов рисунка и инΑекса пигментации Mesobuthus eupeus в посеΛениях из разнотипных (А) и оΑнотипных (В) биотопов в кажΑой из выборок: I – Северо-ЗапаΑный Гобустан; II – Северо-Восточный Гобустан; III – ЦентраΛьный Гобустан; IV – Юго-Восточный Гобустан; V – Юго-Восточный Ширван. ИнΑекс корреΛяции r в преΑеΛах 0.744–0.989; p <0.05. Fig. 26. Comparison of the average values of the frequency of variability of pattern elements and the pigmentation index of Mesobuthus eupeus in conglomerations from habitats of different types (A) and of the same type (B) in each sample: I – northwestern Gobustan; II – northeastern Gobustan; III – central Gobustan; IV – southeastern Gobustan; V – southeastern Shirvan. Correlation index r = 0.744–0.989; p <0.05. in Materials on the colour pattern variability of Mesobuthus eupeus (C.L. Koch, 1839) (Arachnida: Scorpiones) in southeastern Shirvan and Gobustan (Eastern Azerbaijan)
Рис. 26. Сравнение среΑних значений частоты изменчивости эΛементов рисунка и инΑекса пигментации Mesobuthus eupeus в посеΛениях из разнотипных (А) и оΑнотипных (В) биотопов в кажΑой из выборок: I – Северо-ЗапаΑный Гобустан; II – Северо-Восточный Гобустан; III – ЦентраΛьный Гобустан; IV – Юго-Восточный Гобустан; V – Юго-Восточный Ширван. ИнΑекс корреΛяции r в преΑеΛах 0.744–0.989; p <0.05. Fig. 26. Comparison of the average values of the frequency of variability of pattern elements and the pigmentation index of Mesobuthus eupeus in conglomerations from habitats of different types (A) and of the same type (B) in each sample: I – northwestern Gobustan; II – northeastern Gobustan; III – central Gobustan; IV – southeastern Gobustan; V – southeastern Shirvan. Correlation index r = 0.744–0.989; p <0.05.
Eggshell colour differences in a classic example of coevolved eggshell mimicry
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Ecological, genetic and geographical divergence explain differences in sunbird (Nectariniidae) colouration
<p>Bird plumages are among the most elaborate ornaments, displaying almost all colours of the rainbow. Why and how birds are so colourful remains an open question with multiple and sometimes competing hypotheses. Different colours in different patches might have different functions and thus result from different forms of selection (e.g., natural vs. sexual selection). Here we test three hypotheses that might explain colour differences: (1) species isolation, (2) light environment, and (3) Brownian motion. We show that both natural and sexual selection affect the evolution of sunbird colouration, but that their extent and direction differs between sexes, by species interactions, and for different patches across the body. Even though overlap in the light environment explains part of colour differences in species, no colour metric (brightness and chroma) correlates to the light environment. It is likely that these results, where multiple forms of selection influence colouration in different ways, are more general across birds, highlighting the need to investigate bird colouration as a network of individual but inter-connected colour patches.</p>
Data from: Prey colour biases in jumping spiders (Habronattus brunneus) differ across populations
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Evolution of aquatic snails' defences resulted in clade-specific differences in egg toxicity, pigments, and warning colouration
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Ecological, genetic and geographical divergence explain differences in sunbird (Nectariniidae) colouration
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Data from: Fecundity selection on ornamental plumage colour differs between ages and sexes and varies over small spatial scales
Avian plumage colours are some of the most conspicuous sexual ornaments, and yet standardized selection gradients for plumage colour have rarely been quantified. We examined patterns of fecundity selection on plumage colour in blue tits (Cyanistes caeruleus L.). When not accounting for environmental heterogeneity, we detected relatively few cases of selection. We found significant disruptive selection on adult male crown colour and yearling female chest colour and marginally nonsignificant positive linear selection on adult female crown colour. We discovered no new significant selection gradients with canonical rotation of the matrix of nonlinear selection. Next, using a long-term data set, we identified territory-level environmental variables that predicted fecundity to determine whether these variables influenced patterns of plumage selection. The first of these variables, the density of oaks within 50 m of the nest, influenced selection gradients only for yearling males. The second variable, an inverse function of nesting density, interacted with a subset of plumage selection gradients for yearling males and adult females, although the strength and direction of selection did not vary predictably with population density across these analyses. Overall, fecundity selection on plumage colour in blue tits appeared rare and inconsistent among sexes and age classes.
Data from: Significant differences in maternal carotenoid provisioning and effects on offspring fitness in Chinook salmon colour morphs
In oviparous species, maternal carotenoid provisioning can deliver diverse fitness benefits to offspring via increased survival, growth, and immune function. Despite demonstrated advantages of carotenoids, large intra‐ and interspecific variation in carotenoid utilization exists, suggesting trade‐offs associated with carotenoids. In Chinook salmon (Oncorhynchus tshawytscha), extreme variation in carotenoid utilization delineates two colour morphs (red and white) that differ genetically in their ability to deposit carotenoids into tissues. Here, we take advantage of this natural variation to examine how large differences in maternal carotenoid provisioning influence offspring fitness. Using a full‐factorial breeding design crossing morphs and common‐garden rearing, we measured differences in a suite of fitness‐related traits, including survival, growth, viral susceptibility, and host response, in offspring of red (carotenoid‐rich eggs) and white (carotenoid‐poor eggs) females. Eggs of red females had significantly higher carotenoid content than those of white females (6X more); however, this did not translate into measurable differences in offspring fitness. Given that white Chinook salmon may have evolved to counteract their maternal carotenoid deficiency, we also examined the relationship between egg carotenoid content and offspring fitness within each morph separately. Egg carotenoids only had a positive effect within the red morph on survival to eyed‐egg (earliest measured trait), but not within the white morph. While previous work shows that white females benefit from reduced egg predation, our study also supports a hypothesis that white Chinook salmon have evolved additional mechanisms to improve egg survival despite low carotenoids, providing novel insight into evolutionary mechanisms that maintain this stable polymorphism.
Data from: Cryptic differences in colour among Müllerian mimics: how can the visual capacities of predators and prey shape the evolution of wing colours?
Antagonistic interactions between predators and prey often lead to co-evolution. In the case of toxic prey, aposematic colours act as warning signals for predators and play a protective role. Evolutionary convergence in colour patterns among toxic prey evolves due to positive density-dependent selection and the benefits of mutual resemblance in spreading the mortality cost of educating predators over a larger prey assemblage. Comimetic species evolve highly similar colour patterns, but such convergence may interfere with intraspecific signalling and recognition in the prey community, especially for species involved in polymorphic mimicry. Using spectrophotometry measures, we investigated the variation in wing coloration among comimetic butterflies from distantly related lineages. We focused on seven morphs of the polymorphic species Heliconius numata and the seven corresponding comimetic species from the genus Melinaea. Significant differences in the yellow, orange and black patches of the wing were detected between genera. Perceptions of these cryptic differences by bird and butterfly observers were then estimated using models of animal vision based on physiological data. Our results showed that the most strikingly perceived differences were obtained for the contrast of yellow against a black background. The capacity to discriminate between comimetic genera based on this colour contrast was also evaluated to be higher for butterflies than for birds, suggesting that this variation in colour, likely undetectable to birds, might be used by butterflies for distinguishing mating partners without losing the benefits of mimicry. The evolution of wing colour in mimetic butterflies might thus be shaped by the opposite selective pressures exerted by predation and species recognition.
FIGURE. Scatter plots (N=200) and linear regression lines of the length and diameter of termite coprolites from the Lower Cretaceous Huolinhe Formation in eastern Inner Mongolia, China. The grey shading represents the 95% confidence interval of linear relationship. Note scatter plots depicting a k-means clustering analysis reveals three groups, indicated by circles of different colours; stars of different colour mean the clusters centroids which are the average length and diameter. in Termite coprolites (Blattodea: Isoptera) from the Early Cretaceous of eastern Inner Mongolia, Northeast China
FIGURE. Scatter plots (N=200) and linear regression lines of the length and diameter of termite coprolites from the Lower Cretaceous Huolinhe Formation in eastern Inner Mongolia, China. The grey shading represents the 95% confidence interval of linear relationship. Note scatter plots depicting a k-means clustering analysis reveals three groups, indicated by circles of different colours; stars of different colour mean the clusters centroids which are the average length and diameter.
Data from: Discrete colour polymorphism in the tawny dragon lizard (Ctenophorus decresii) and differences in signal conspicuousness among morphs
Intraspecific colour variation is common in nature and can vary from the coexistence of discrete colour variants in polymorphic species to continuous variation. Whether coloration is continuous or discrete is often ambiguous and many species exhibit a combination of the two. The nature of the variation (discrete or continuous) has implications for both the genetic basis of the colour variation and the evolutionary processes generating and maintaining it. Consequently, it is important to qualify the existence of discrete morphs, particularly in relation to the animal's visual system. In this study, we quantified male throat colour variation in Ctenophorus decresii tawny dragon lizard and tested for morphological and ecological correlates of the colour variants. We confirmed that discrete throat colour morphs can be defined based on colour and pattern analyses independent of the human visual system. We also found that the colour variants differed in their conspicuousness from the background, to the lizard's visual system, which has implications for signalling. However, the morphs did not differ in morphology or microhabitat use, which suggests that these characteristics are not involved in the evolutionary maintenance of the polymorphism.
Data from: Colour change on different body regions provides thermal and signalling advantages in bearded dragon lizards
Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300–700 nm) and near-infrared (NIR; 700–2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards (Pogona vitticeps) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.
Great tit predation on colour morphs of the wood tiger moth at different relative frequencies
<p>Polymorphic warning signals in aposematic systems are enigmatic because predator learning should favor the most common form, creating positive frequency-dependent survival. However, many populations exhibit variation in warning signals. There are various selective mechanisms which can counter positive frequency-dependent selection and lead to temporal or spatial warning signal diversification. Examining these mechanisms and their effects requires first confirming whether the most common morphs are favored at both local and regional scales. Empirical examples of this are uncommon and often include potentially confounding factors such as a lack of knowledge of predator identity and behavior. We tested how bird behavior influences the survival of three coexisting morphs of the aposematic wood tiger moth <i>Arctia plantaginis </i>offered to a sympatric predator (great tits, <i>Parus major</i>) at different frequencies.<i> </i>We found that although positive frequency-dependent selection is present, its strength is affected by predator characteristics and varying prey profitability. These results highlight the need to understand predator foraging in natural communities with variable prey defences, in order to better examine how behavioral interactions shape evolutionary outcomes.</p>
Data from: Discrete colour polymorphism in the tawny dragon lizard (Ctenophorus decresii) and differences in signal conspicuousness among morphs
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Data from: Significant differences in maternal carotenoid provisioning and effects on offspring fitness in Chinook salmon colour morphs
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Data from: Cryptic differences in colour among Müllerian mimics: how can the visual capacities of predators and prey shape the evolution of wing colours?
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Data from: Proximate mechanisms of colour variation in the frillneck lizard: geographical differences in pigment contents of an ornament
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