Habitat light, colour variation, and ultraviolet reflectance in the Grand Cayman anole, Anolis conspersus
01 Jul 2001-Biological Journal of The Linnean Society (No longer published by Elsevier)-Vol. 73, Iss: 3, pp 299-320
TL;DR: Evidence is presented to show how geological, ecological, and physiological factors could have interacted to select for a short wavelength-reflective dewlap from a long wavelength- reflective precursor following the colonization of Grand Cayman from Jamaica by A. grahami between 2 and 3 Mya.
Abstract: Data from a diversity of sources are consistent with the hypothesis that the Grand Cayman anole, Anolis conspersus, is descended directly from Anolis grahami of Jamaica. Although the two species have remained morphologically similar, coloration in A. conspersus has changed considerably from that of its ancestor. The most dramatic difference is seen in dewlap colour, where A. conspersus has evolved a blue and highly UV-reflective dewlap from the ancestral orange-and-yellow colour state. In addition, variation in normal (non-metachrosis) dorsum coloration in A. grahami populations is limited to shades of green (olive, emerald, teal), whereas in A. conspersus dorsum coloration varies from green to blue and to brown. This increased colour variation occurs despite Grand Cayman being a small, relatively featureless island only 35 km in length. Results of this study suggest that ambient light differences associated with precipitation-related vegetation structure may have played an important role in the evolution of A. conspersus body colour variation. Evidence is presented to show how geological, ecological, and physiological factors could have interacted to select for a short wavelength-reflective dewlap from a long wavelength-reflective precursor following the colonization of Grand Cayman from Jamaica by A. grahami between 2 and 3 Mya.
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TL;DR: Specific, testable functional hypotheses are offered for the most common pigmentary and structural components of vertebrate colour patches and how multiple trait evolution theory can be applied to the components of single colour patches.
Abstract: Colour patches are complex traits, the components of which may evolve independently through a variety of mechanisms. Although usually treated as simple, two-dimensional characters and classified as either structural or pigmentary, in reality colour patches are complicated, three-dimensional structures that often contain multiple pigment types and structural features. The basic dermal chromatophore unit of fishes, reptiles and amphibians consists of three contiguous cell layers. Xanthophores and erythrophores in the outermost layer contain carotenoid and pteridine pigments that absorb short-wave light; iridophores in the middle layer contain crystalline platelets that reflect light back through the xanthophores; and melanophores in the basal layer contain melanins that absorb light across the spectrum. Changes in any one component of a chromatophore unit can drastically alter the reflectance spectrum produced, and for any given adaptive outcome (e.g. an increase in visibility), there may be multiple biochemical or cellular routes that evolution could take, allowing for divergent responses by different populations or species to similar selection regimes. All of the mechanisms of signal evolution that previously have been applied to single ornaments (including whole colour patches) could potentially be applied to the individual components of colour patches. To reach a complete understanding of colour patch evolution, however, it may be necessary to take an explicitly multi-trait approach. Here, we review multiple trait evolution theory and the basic mechanisms of colour production in fishes, reptiles and amphibians, and use a combination of computer simulations and empirical examples to show how multiple trait evolution theory can be applied to the components of single colour patches. This integrative perspective on animal colouration opens up a host of new questions and hypotheses. We offer specific, testable functional hypotheses for the most common pigmentary (carotenoid, pteridine and melanin) and structural components of vertebrate colour patches.
245 citations
TL;DR: It is found that populations from mesic and xeric conditions occupy two distinct habitats with respect to light intensity and spectral quality and that dewlap design has diverged between populations in a way that increases signal detectability in each habitat.
Abstract: We tested the prediction of the sensory drive hypothesis using four allopatric populations of the lizard Anolis cristatellus from two distinct environments (i.e., mesic and xeric conditions). For each population, we measured habitat light characteristics and quantified signal design by measuring the spectral and total reflectance and transmittance of the dewlap. We used these data to calculate dewlap detectability using an empirically based model of signal detection probability. We found that populations from mesic and xeric conditions occupy two distinct habitats with respect to light intensity and spectral quality and that dewlap design has diverged between populations in a way that increases signal detectability in each habitat. The major difference in dewlap design was in total reflectance and transmittance, making dewlaps from xeric habitats darker and dewlaps from mesic habitats brighter. Furthermore, dewlap detection decreased significantly when a dewlap from a xeric habitat is detected u...
230 citations
Cites background from "Habitat light, colour variation, an..."
...Second, there is evidence that differences in habitat light conditions have selected for different color patterns in different microhabitats (i.e., selection through the process of sensory drive; Fleishman et al. 1993; Fleishman 2000; Macedonia 2001; Leal and Fleishman 2002)....
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...vol. 163, no. 1 the american naturalist january 2004 Differences in Visual Signal Design and Detectability between Allopatric Populations of Anolis Lizards Manuel Leal* and Leo J. Fleishman† Department of Biology, Union College, Schenectady, New York 12308...
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TL;DR: It is found that the chromatic and brightness contrasts of golden patches used during courtship are greater against the cleared court than against adjacent litter, and that cleared courts provide a less variable background for these color patches, resulting in displays that consistently contrast the visual background.
Abstract: Effective visual communication requires signals that are easy to detect, transmit, receive, and discriminate. Animals can increase the probability that their visual signals would be detected by evolving signals that contrast with their visual background. Animals can further enhance this contrast by behaviorally modifying the existing visual background. Male golden-collared manakins (Manacus vitellinus) clear leaf litter from the ground to form courts, which are used as display arenas. Using reflectance measures of the signal (male plumage) and the visual background (cleared court and adjacent litter), the irradiance measures of ambient light during display, and published measures of photoreceptor sensitivity of a Passerine, we test the hypothesis that court-clearing augments the contrast between male plumage and the visual background. We find that the chromatic and brightness contrasts of golden patches used during courtship are greater against the cleared court than against adjacent litter. In addition, we find that cleared courts provide a less variable background for these color patches, resulting in displays that consistently contrast the visual background. These results suggest that behavioral modification of the visual background may act to increase the conspicuousness of colorful male plumage during display, providing an explanation for why golden-collared manakins, and possibly other species, build or clear display courts. Key words: chromatic contrasts, court-clearing, Manacus vitellinus, manakins, signaling, visual signals. [Behav Ecol 15:1003–1010 (2004)]
146 citations
TL;DR: D dwarf chameleons showed different behavioural responses, including colour change, towards multiple predators that detect and capture prey in different ways, and whether these antipredator responses varied geographically was consistent among populations.
Abstract: Potential prey are often exposed to multiple predators that vary in their foraging tactics and ability to detect prey. For animals that rely on crypsis to avoid predators, one solution is to alter their behaviour or appearance to maximize crypsis in ways that are specific to different types of predator. We tested whether dwarf chameleons (Bradypodion transvaalense) showed different behavioural responses, including colour change, towards multiple predators (bird and snake models) that detect and capture prey in different ways, and whether these antipredator responses varied geographically. Chameleons consistently used the same body postures (lateral compression and flipping to the opposite side of the branch) and displayed similar chromatic (colour) contrast against the natural background in response to both predator types. However, they became significantly more achromatically contrasting (brighter) in the presence of the snake compared to the bird. This relative difference in achromatic contrast towards the two types of predator was consistent among populations. There were also significant differences in both absolute achromatic and chromatic contrast among populations despite very similar light environment, background coloration and habitat structure. Our results highlight facultative crypsis as one type of flexible antipredator tactic and emphasize the importance of visual ecology in understanding prey–predator interactions. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 437–446.
143 citations
Cites methods from "Habitat light, colour variation, an..."
...The contrast measures we used are simple measures of contrast in radiance (Endler, 1990; Macedonia, 2001; Heindl & Winkler, 2003)....
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...The contrast measures we used are simple measures of contrast in radiance (Endler, 1990; Macedonia, 2001; Heindl & Winkler, 2003)....
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...and background, respectively, integrated over 320‐ 700 nm. To calculate chromatic contrast, all radiance spectra of the chameleons and backgrounds were standardized for brightness (area under the curve 320‐ 700 nm = 1). Chromatic contrast was then calculated as the Euclidean distance ( D s ) between the radiance spectrum of the chameleon vs. background (Endler, 1990; Macedonia, 2001; Heindl & Winkler, 2003), using:...
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...Chromatic contrast was then calculated as the Euclidean distance ( D s ) between the radiance spectrum of the chameleon vs. background (Endler, 1990; Macedonia, 2001; Heindl & Winkler, 2003), using: where Q t ( λ ) and Q b ( λ ) is the radiance at a given wavelength and summation is over each 5 nm…...
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TL;DR: The results confirmed that there are real differences in crypsis conspicuousness both between populations and between sexes; that exposed body regions were significantly more cryptic than hidden ones, particularly in females; and that females, but not males, are more cryptic against their own local background than against the background of other populations.
Abstract: Many animal species display striking color differences with respect to geographic location, sex, and body region. Traditional adaptive explanations for such complex patterns invoke an interaction between selection for conspicuous signals and natural selection for crypsis. Although there is now a substantial body of evidence supporting the role of sexual selection for signaling functions, quantitative studies of crypsis remain comparatively rare. Here, we combine objective measures of coloration with information on predator visual sensitivities to study the role of crypsis in the evolution of color variation in an Australian lizard species complex (Ctenophorus decresii). We apply a model that allows us to quantify crypsis in terms of the visual contrast of the lizards against their natural backgrounds, as perceived by potential avian predators. We then use these quantitative estimates of crypsis to answer the following questions. Are there significant differences in crypsis conspicuousness among populations? Are there significant differences in crypsis conspicuousness between the sexes? Are body regions "exposed" to visual predators more cryptic than "hidden" body regions? Is there evidence for local adaptation with respect to crypsis against different substrates? In general, our results confirmed that there are real differences in crypsis conspicuousness both between populations and between sexes; that exposed body regions were significantly more cryptic than hidden ones, particularly in females; and that females, but not males, are more cryptic against their own local background than against the background of other populations. Body regions that varied most in contrast between the sexes and between populations were also most conspicuous and are emphasized by males during social and sexual signaling. However, results varied with respect to the aspect of coloration studied. Results based on chromatic contrast ("hue" of color) provided better support for the crypsis hypothesis than did results based on achromatic contrast ("brightness" of color). Taken together, these results support the view that crypsis plays a substantial role in the evolution of color variation and that color patterns represent a balance between the need for conspicuousness for signaling and the need for crypsis to avoid predation.
137 citations
References
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TL;DR: It is argued that species recognition in anoline lizards is not based on a single sign stimulus or releaser but on a complex of stimuli, separately and in various combinations identify the display animal.
Abstract: synopsis. Although having a number of functions in reproductive, territorial and aggres? sive behavior, Anolis dewlaps are only one means of intraspecific signaling and they are always present in small anole faunas (e.g., those of one or two species islands) but here, in contrast to the situation in large faunas, their color and pattern appear usually very similar and appear to be unimportant for species (or population) recognition. The latter function is then performed by such characteristics as adult size and body color and pattern. Where, however, numerous species abut or overlap, dewlap color and pattern tend to be diverse and diagnostic (particularly between overlapping forms). Even here, however, adult size, body shape and body color often redundandy reinforce the species and population recognition function of even marked dewlap difference. In certain cases in complex faunas, size and/or body pattern substitute for the species recognition function of reduced or absent dewlaps. In Rand and Williams (1970) we argued that species recognition in anoline lizards is not based on a single sign stimulus or releaser but on a complex of stimuli, re? dundant to each other, which separately and in various combinations identify the display animal. Because natural selection insists that mates be recognizable under a variety of conditions, we have argued that selection must favor a system in which species identity is encoded redundantly. In the specific case analyzed by us in 1970?species recognition in the eight species sympatric at a single locality, La Palma, on the Greater Antillean island of Hispaniola?we found that each of the eight species differed from the rest in several (average 2-*/2) characteristics ofthe dewlap. Thus the dewlap alone sufHced to
96 citations
TL;DR: An integrated color change mechanism that accounts for both ontogenetic and seasonal color changes at the cellular level is hypothesized.
Abstract: Adult male Sceloporus undulatus erythrocheilus possess ventral color patches that are used to communicate social status. Three discrete color morphs occur in natural populations, two that are prevalent (orange and yellow morphs) and one that is rare (melanized morph). We sought to describe the cellular basis of bright ventral coloration. Contributions of each of three types of chromatophores (xanthophores, iridophores, and melanophores) to overall tissue color in orange, yellow, gray, and blue tissues were determined by transmission electron microscopy and thin-layer chromatography. Qualitative differences occurred among all three color morphs. Additionally, an integrated color change mechanism that accounts for both ontogenetic and seasonal color changes at the cellular level is hypothesized.
91 citations
01 Nov 1986-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: Anolis, which rely upon motion to detect objects in the periphery of the visual field, filter out irrelevant motion such as that of windblown vegetation by responding preferentially to particular patterns of motion and the way motion of a backdrop of vegetation affects the response.
Abstract: 1.
Anolis lizards respond to a moving object viewed in the periphery of their visual field by turning their eye to fixate the object with their central fovea. This paper describes the relative effectiveness of different patterns of motion of a small black lure in eliciting these eye movements and the way motion of a backdrop of vegetation affects the response.
2.
The stimulus was positioned 45° from the animal's line of gaze and oscillated in the vertical axis at different frequencies between 0.5 and 10 Hz. At each frequency, the amplitude of the oscillation was increased until the lizard flicked its eye towards the stimulus. The minimum amplitude needed for response (0.22° of visual angle) was independent of frequency and waveform. The probability of any response occurring was, however, lower at higher frequencies (7 and 10 Hz) and a 1.5 Hz square wave evoked the greatest proportion of responses.
3.
Sinusoidal oscillation of a background of vegetation at 1.6 Hz during or before motion of the stimulus lure reduced the probability of an eye flick but did not raise the minimum amplitude needed for a response. The suppressive effect was greatest when the lure was oscillated at frequencies close to that of the background. It is concluded thatAnolis, which rely upon motion to detect objects in the periphery of the visual field, filter out irrelevant motion such as that of windblown vegetation by (1) responding preferentially to particular patterns of motion and (2) short term habituation to commonly present patterns of motion.
90 citations
TL;DR: Adult male Anolis grahami was presented with colour-videotaped sequences of displays from conspecifics and from three heterospecific species of anoles, and there was no indication of discrimination among the displays of the three congeneric species.
Abstract: The visual displays of male anoles (Anolis sp.) are usually viewed as characters that facilitate species recognition. This presumption stems largely from the extensive variation in the head bobbing movements and dewlap colouration in males of this genus. However, few experimental data exist that illuminate the importance of these visual signals for species recognition. We presented adult male Anolis grahami with colour-videotaped sequences of displays from conspecifics and from three heterospecific species of anoles. The congenerics (A. carolinensis, A. conspersus, and A. sagrei) were chosen on the basis of their phylogenetic and geographical relationships with A. grahami. Stimulus males were filmed at a constant distance and orientation from the video camera, and edited sequences of their displays were presented at a standard distance from subjects. Video playbacks allowed us to equalize the quantity of display performed by each stimulus species, and to eliminate stimulus/subject interactions as well as inter-trial variation in stimulus behaviour. Results revealed that the subjects responded more strongly to conspecific than to heterospecific displays on all behavioural variables examined, but there was no indication of discrimination among the displays of the three congeneric species.
88 citations
TL;DR: The results suggest that thebest environment for producing bright-red coloration may not be the best environment for favorable expression of life history characters, especially under stressful conditions.
Abstract: Many ladybird beetles respond to a potential predation event by `reflex bleeding' or secreting a noxious defensive chemical that is similar to hemolymph. Both adults and larvae show this response. Reflex bleeding is known to reduce predator attack rates and increase prey survival after an attack, especially when reflex bleeding is employed in combination with other cues such as odor and warning coloration. In this experiment, we examined how variability in the number of reflex bleeding events and food quality in the larval stage of the aposematic ladybird beetle Harmonia axyridis affected elytral color, development time, and terminal size in adults. Effects of reflex bleeding were subtle and may have been influenced by diet treatments. Adult color did not differ between bleed treatment groups but beetles that reflex bled tended to take longer to develop and grow to smaller sizes than control group beetles. There were clear and strong effects of larval diet on adult phenotype: an ad libitum pollen diet resulted in paler adult coloration, shorter development time, and larger adult size relative to a limited-availability aphid diet. Our results suggest that the best environment for producing bright-red coloration may not be the best environment for favorable expression of life history characters, especially under stressful conditions. Interactions between different life history stages of H. axyridis are also discussed.
86 citations