Repeated evolution of exaggerated dewlaps and other throat morphology in lizards

Abstract

The existence of elaborate ornamental structures in males is often assumed to reflect the outcome of female mate choice for showy males. However, female mate choice appears weak in many iguanian lizards, but males still exhibit an array of ornament‐like structures around the throat. We performed a phylogenetic comparative study to assess whether these structures have originated in response to male–male competition or the need for improved signal efficiency in visually difficult environments. We found little evidence for the influence of male–male competition. Instead, forest species were more likely to exhibit colourful throat appendages than species living in open habitats, suggesting selection for signal efficiency. On at least three independent occasions, throat ornamentation has become further elaborated into a large, conspicuously coloured moving dewlap. Although the function of the dewlap is convergent, the underlying hyoid apparatus has evolved very differently, revealing the same adaptive outcome has been achieved through multiple evolutionary trajectories. More generally, our findings highlight that extravagant, ornament‐like morphology can evolve in males without the direct influence of female mate choice and that failure to consider alternative hypotheses for the evolution of these structures can obscure the true origins of signal diversity among closely related taxa.

In Space and Time: Territorial Animals are Attracted to Conspecific Chemical Cues

“…There is little evidence of female choice shaping the evolution of male signals in lizards (e.g., Ord et al 2015), and it seems likely that female lizards choose among territories rather than male phenotypes (but see Swierk et al 2012). Female attraction to the chemical cues in our study may reflect female attraction to novel males or to the combined signals of more than one male, as has been shown for Iberian rock lizards (Martín & López 2013b).…”

Variation in Display Behavior, Ornament Morphology, Sexual Size Dimorphism, and Habitat Structure in the Fan-Throated Lizard (Sitana, Agamidae)

“…Therefore, environmental context likely does not play a role in maintaining variation in ornament morphology in Fan-Throated Lizards, similar to other agamid lizards (e.g. Chen et al, 2012); however, this is in contrast with Anolis lizards which bear a throat-fan that is functionally similar to that of Sitana (Ord et al, 2015). Changes in visual environment from xeric to mesic forests are correlated with variation in throat-fan coloration within Anolis species in a manner that is consistent with selection for maximum conspicuousness of the throat-fan in each habitat (Leal and Fleishman, 2004;Ng et al, 2013).…”

Sexual selection and the chemical signal design of lacertid lizards

“…In a sexual selection context, the sender is most often a male, broadcasting information about aspects of its quality towards rival males, females on heat or both. Intersexual selection through female choice is generally regarded the most important driver of signal evolution (Andersson, 1994;Ord et al, 2001), but, in lizards, female choice seems rare (Olsson & Madsen, 1995;Tokarz, 1995;LeBas & Marshall, 2000;Lailvaux & Irschick, 2006;Ord et al, 2015). Accordingly, the evolution of elaborate coloration, ornamentation or display behaviour in lizards is usually explained in terms of intensified intrasexual selection (Ord et al, 2001;Chen et al, 2012;Pérez i de Lanuza et al, 2013).…”