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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01 Jan 1978
TL;DR: In this paper, the authors explore the factors that determine color patterns under various specific conditions and show that the actual pattern evolved in a particular place represents a compromise between factors which favor crypsis and those which favor conspicuous color patterns.
Abstract: It has long been known that the general colors and tones of animals tend to match their backgrounds (E. Darwin, 1794; Poulton, 1890). The adaptive significance of this has been borne out in numerous experimental studies (DiCesnola, 1904; Sumner, 1934, 1935; Isley, 1938; Popham, 1942; Dice, 1947; Turner, 1961; Kettlewell, 1956, 1973; Kaufman, 1974; Wiklund, 1975; Curio, 1976). There is also a good understanding of warning coloration (Cott, 1940; Wickler, 1968; Edmunds, 1974; Rothschild, 1975). However, the determinants of color pattern are poorly known, although it is known in a general way that the patterns and forms of animals are similar to their backgrounds (Poulton, 1890; Thayer, 1909; Cott, 1940; Wickler, 1968; Robinson, 1969; Edmunds, 1974; Fogden and Fogden, 1974). It is the purpose of this paper to explore the factors that determine color patterns under various specific conditions. The basic assumption is that a color pattern must resemble a random sample of the background seen by predators in order to be cryptic, and must deviate from the background in one or more ways in order to be conspicuous. As a result, the actual pattern evolved in a particular place represents a compromise between factors which favor crypsis and those which favor conspicuous color patterns.
1,096 citations
TL;DR: This work investigated three lekking birds at Nourages field station, French Guiana and found that Conspicuousness is a function of ambient light spectra during displays and the reflectance spectra of color pattern elements of the birds and their visual backgrounds.
Abstract: Forests exhibit a mosaic of different spectral environments that arise from forest geometry and weather If visual signals are used in mate choice, then forest geometry and weather will affect reproductive behavior because the appearance of a visual signal depends on the joint effects of ambient light and the animal's reflectance spectra We investigated three lekking birds at Nourages field station, French Guiana: Rupicola rupicola, Corapipo gutturalis, and Lepidothrix serena Conspicuousness is a function of ambient light spectra during displays and the reflectance spectra of color pattern elements of the birds and their visual backgrounds Each species places its lek and performs its lek displays in only one or two of the available light environments, and some may specialize in the more extreme spectra even within each light environment The color patterns and behavior of each species maximize its visual contrast during its display and reduce it off the lek or on the lek but not displaying Each specie
495 citations
"Habitat light, colour variation, an..." refers background in this paper
...Forest shade occurs under a closed canopy whereand birds (Endler & Thery, 1996) have been important virtually all of the ambient light has been filteredin demonstrating the influence of habitat light and through and reflected from the foliage....
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TL;DR: Color patterns of natural populations of guppies (Poecilia reticulata) are a compromise between sexual selection and predation avoidance and relatively less conspicuous at the times and places of maximum predator risk.
473 citations
"Habitat light, colour variation, an..." refers background in this paper
...…(e.g. contrasting borders,benefit to reproductive success through male–male central spots, colour combinations) as well as dif-competition and female choice, and the cost of being ferences in body coloration (Williams & Rand, 1970).detected by predators (e.g. Endler, 1991, 1992; Ortolani, 1999)....
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...Studies of guppies (e.g. Endler, 1991) metry....
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...2001 The Linnean Society of London ADDITIONAL KEY WORDS: Anolis lizards – visual signals – colour evolution – dewlap – ultraviolet – colour segment classification – principal components analysis – habitat light. patterns that minimize predator detection while re-INTRODUCTION maining conspicuous to the species in which the signal Signal evolution is driven by details of signal per- has evolved. ceivers’ sensory systems and characteristics of the environment that enhance or diminish signal trans- FOREST LIGHT HABITATS AND THEIR CONSEQUENCES mission (e.g. Endler, 1991, 1992)....
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...…conspicuous to the species in which the signal Signal evolution is driven by details of signal per- has evolved. ceivers’ sensory systems and characteristics of the environment that enhance or diminish signal trans- FOREST LIGHT HABITATS AND THEIR CONSEQUENCES mission (e.g. Endler, 1991, 1992)....
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TL;DR: Light intensity and predation had significant effects on male courtship behaviour in guppies and reduced the need for an evolutionary compromise between colour patterns that reduce the risk of visual predation and those that increase visibility to females.
452 citations
TL;DR: This study revealed previously unnoticed sex differences in plumage coloration and the nature of iridescent and noniridescent sex differences, which has important implications for classifications of animals as mono‐ or dimorphic and for taxonomic and conservation purposes.
Abstract: Assessment of color using human vision (or standards based thereon) is central to tests of many evolutionary hypotheses. Yet fundamental differences in color vision between humans and other animals call this approach into question. Here we use techniques for objectively assessing color patterns that avoid reliance on species‐specific (e.g., human) perception. Reflectance spectra are the invariant features that we expect the animal's color cognition to have evolved to extract. We performed multivariate analyses on principal components derived from >2,600 reflectance spectra (300–720 nm) sampled in a stratified random design from different body regions of male and female starlings in breeding plumage. Starlings possess spatially complex plumage patterns and extensive areas of iridescence. Our study revealed previously unnoticed sex differences in plumage coloration and the nature of iridescent and noniridescent sex differences. Sex differences occurred in some body regions but not others, were mor...
423 citations
"Habitat light, colour variation, an..." refers background or methods in this paper
...Following these analyses a PCA wasized with a 100 kHz A/D card (National Instruments run on the 38 spectral segment means of the habitatDAQCard-700) using a Compaq Armada 1130 laptop irradiance data (see Cuthill et al., 1999 for a detailedcomputer....
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...morphs, peaking at 340 nm (mean=339.5, SD=2.5, Grill & Moore, 1998; Cuthill et al., 1999), the PC con=22) and decreasing monotonically with increasing efficients represent chroma and hue (Fig....
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...…reflectance was similar for all three colour cause brightness was equalized prior to analysis (e.g. morphs, peaking at 340 nm (mean=339.5, SD=2.5, Grill & Moore, 1998; Cuthill et al., 1999), the PC con=22) and decreasing monotonically with increasing efficients represent chroma and hue (Fig....
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