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Evolution of Anolis lizard dewlap diversity.

Nicholson KE, Harmon LJ, Losos JB - PLoS ONE (2007)

Bottom Line: We found that dewlap configurations (sizes, patterns and colors) exhibit substantial diversity, but that most are easily categorized into six patterns that incorporate one to three of 13 recognizable colors.We found no support for the Ecomorph Convergence hypothesis; species using the same structural habitat were no more similar in dewlap configuration than expected by chance.Our data do not support two hypothesized explanations for this diversity, but others such as sexual selection remain to be tested.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Central Michigan University, Mt. Pleasant, Michigan, United States of America. kirsten.nicholson@cmich.edu

ABSTRACT

Background: The dewlaps of Anolis lizards provide a classic example of a complex signaling system whose function and evolution is poorly understood. Dewlaps are flaps of skin beneath the chin that are extended and combined with head and body movements for visual signals and displays. They exhibit extensive morphological variation and are one of two cladistic features uniting anoles, yet little is known regarding their function and evolution. We quantified the diversity of anole dewlaps, investigated whether dewlap morphology was informative regarding phylogenetic relationships, and tested two separate hypotheses: (A) similar Anolis habitat specialists possess similar dewlap configurations (Ecomorph Convergence hypothesis), and (B) sympatric species differ in their dewlap morphologies to a greater extent than expected by chance (Species Recognition hypothesis).

Methodology/principal findings: We found that dewlap configurations (sizes, patterns and colors) exhibit substantial diversity, but that most are easily categorized into six patterns that incorporate one to three of 13 recognizable colors. Dewlap morphology is not phylogenetically informative and, like other features of anoles, exhibits convergence in configurations. We found no support for the Ecomorph Convergence hypothesis; species using the same structural habitat were no more similar in dewlap configuration than expected by chance. With one exception, all sympatric species in four communities differ in dewlap configuration. However, this provides only weak support for the Species Recognition hypothesis because, due to the great diversity in dewlap configurations observed across each island, few cases of sympatric species with identical dewlaps would be expected to co-occur by chance alone.

Conclusions/significance: Despite previous thought, most dewlaps exhibit easily characterizable patterns and colorations. Nevertheless, dewlap variation is extensive and explanations for the origin and evolution of this diversity are lacking. Our data do not support two hypothesized explanations for this diversity, but others such as sexual selection remain to be tested.

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Related in: MedlinePlus

A small sample of Anolis dewlaps exemplifying observed morphological diversity. Some images are modified from original photographs and used with permission from David Hillis and Richard Glor. Species depicted are as follows (in order right to left and top to bottom): A. pulchellus, A. sericeus, A. liogaster, A. longitibalis, A. cobanensis, A. gorgonae, A. cristatellus, A. chlorocyanus, A. reconditus, A. christophei, A. cuprinus, A. new species, A. lineatopus, A. annectens, A. baleatus, A. auratus.
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pone-0000274-g001: A small sample of Anolis dewlaps exemplifying observed morphological diversity. Some images are modified from original photographs and used with permission from David Hillis and Richard Glor. Species depicted are as follows (in order right to left and top to bottom): A. pulchellus, A. sericeus, A. liogaster, A. longitibalis, A. cobanensis, A. gorgonae, A. cristatellus, A. chlorocyanus, A. reconditus, A. christophei, A. cuprinus, A. new species, A. lineatopus, A. annectens, A. baleatus, A. auratus.

Mentions: The dewlaps of Anolis lizards present a classic example of a complex signaling system whose function and evolution is poorly understood. A characteristic and charismatic feature of Anolis, the dewlap consists of a flap of skin below the chin that is supported by the second ceratobranchial cartilage, a modification of the hyoid apparatus [10]–[11]. Dewlaps vary dramatically in size, shape, color, and pattern (Figure 1), and are frequently used to delineate species boundaries (e.g., see 12 and references therein). Anoles extend and retract their dewlaps in various temporal patterns, frequently combined with head and other body movements, that are thought to communicate mating and territorial interests [4], [13], as well as being used in predator deterrence [14]. In addition, the cadence of head-bobbing used in these visual displays appears to be species specific [4 and references therein].


Evolution of Anolis lizard dewlap diversity.

Nicholson KE, Harmon LJ, Losos JB - PLoS ONE (2007)

A small sample of Anolis dewlaps exemplifying observed morphological diversity. Some images are modified from original photographs and used with permission from David Hillis and Richard Glor. Species depicted are as follows (in order right to left and top to bottom): A. pulchellus, A. sericeus, A. liogaster, A. longitibalis, A. cobanensis, A. gorgonae, A. cristatellus, A. chlorocyanus, A. reconditus, A. christophei, A. cuprinus, A. new species, A. lineatopus, A. annectens, A. baleatus, A. auratus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1803026&req=5

pone-0000274-g001: A small sample of Anolis dewlaps exemplifying observed morphological diversity. Some images are modified from original photographs and used with permission from David Hillis and Richard Glor. Species depicted are as follows (in order right to left and top to bottom): A. pulchellus, A. sericeus, A. liogaster, A. longitibalis, A. cobanensis, A. gorgonae, A. cristatellus, A. chlorocyanus, A. reconditus, A. christophei, A. cuprinus, A. new species, A. lineatopus, A. annectens, A. baleatus, A. auratus.
Mentions: The dewlaps of Anolis lizards present a classic example of a complex signaling system whose function and evolution is poorly understood. A characteristic and charismatic feature of Anolis, the dewlap consists of a flap of skin below the chin that is supported by the second ceratobranchial cartilage, a modification of the hyoid apparatus [10]–[11]. Dewlaps vary dramatically in size, shape, color, and pattern (Figure 1), and are frequently used to delineate species boundaries (e.g., see 12 and references therein). Anoles extend and retract their dewlaps in various temporal patterns, frequently combined with head and other body movements, that are thought to communicate mating and territorial interests [4], [13], as well as being used in predator deterrence [14]. In addition, the cadence of head-bobbing used in these visual displays appears to be species specific [4 and references therein].

Bottom Line: We found that dewlap configurations (sizes, patterns and colors) exhibit substantial diversity, but that most are easily categorized into six patterns that incorporate one to three of 13 recognizable colors.We found no support for the Ecomorph Convergence hypothesis; species using the same structural habitat were no more similar in dewlap configuration than expected by chance.Our data do not support two hypothesized explanations for this diversity, but others such as sexual selection remain to be tested.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Central Michigan University, Mt. Pleasant, Michigan, United States of America. kirsten.nicholson@cmich.edu

ABSTRACT

Background: The dewlaps of Anolis lizards provide a classic example of a complex signaling system whose function and evolution is poorly understood. Dewlaps are flaps of skin beneath the chin that are extended and combined with head and body movements for visual signals and displays. They exhibit extensive morphological variation and are one of two cladistic features uniting anoles, yet little is known regarding their function and evolution. We quantified the diversity of anole dewlaps, investigated whether dewlap morphology was informative regarding phylogenetic relationships, and tested two separate hypotheses: (A) similar Anolis habitat specialists possess similar dewlap configurations (Ecomorph Convergence hypothesis), and (B) sympatric species differ in their dewlap morphologies to a greater extent than expected by chance (Species Recognition hypothesis).

Methodology/principal findings: We found that dewlap configurations (sizes, patterns and colors) exhibit substantial diversity, but that most are easily categorized into six patterns that incorporate one to three of 13 recognizable colors. Dewlap morphology is not phylogenetically informative and, like other features of anoles, exhibits convergence in configurations. We found no support for the Ecomorph Convergence hypothesis; species using the same structural habitat were no more similar in dewlap configuration than expected by chance. With one exception, all sympatric species in four communities differ in dewlap configuration. However, this provides only weak support for the Species Recognition hypothesis because, due to the great diversity in dewlap configurations observed across each island, few cases of sympatric species with identical dewlaps would be expected to co-occur by chance alone.

Conclusions/significance: Despite previous thought, most dewlaps exhibit easily characterizable patterns and colorations. Nevertheless, dewlap variation is extensive and explanations for the origin and evolution of this diversity are lacking. Our data do not support two hypothesized explanations for this diversity, but others such as sexual selection remain to be tested.

Show MeSH
Related in: MedlinePlus