Evolution of Anolis Lizard Dewlap Diversity

Abstract

BackgroundThe 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 FindingsWe 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/SignificanceDespite 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.

First record of the invasive Brown Anole, Anolis sagrei Duméril & Bibron, 1837 (Squamata: Iguanidae: Dactyloinae), in South America

“…We compared the morphological characteristics of our specimens with information reported by Poe (2004); Nicholson et al (2007); Losos (2009) & Nicholson et al (2012 to confirm that our specimens fall into the diagnostic characteristics of A. sagrei. The males of A. sagrei are characterized by having a red-orange dewlap, sometimes with a yellow border or blotches.…”

A performance-based cost to honest signalling in male green anole lizards (Anolis carolinensis)

“…Although the costs of dewlap production are relatively low, honesty could also be maintained by high receiverindependent costs of dewlap display. Just as bite force may be important to more than just male combat, dewlaps are thought to have several different signalling functions in a variety of intra-and interspecific ecological contexts in Anolis [70,71]. If displaying in any or all of these contexts incurs fitness costs through, for example, increased likelihood of predation, then dewlap size might possibly be constrained by receiver-independent costs, regardless of the cost of bite force expression.…”

Colorful displays signal male quality in a tropical anole lizard

“…The dewlap is a signal of male fighting ability (Vanhooydonck et al 2005), and its behavioral use is thought to influence mating success (Tokarz et al 2005). However, the communication role of dewlap color is not clear (Nicholson et al 2007) and it is unknown whether signal color and display behavior interact to indicate advertiser condition.…”