Geographic variation in aggressive signalling behaviour of the Jacky dragon

Marco D. Barquero, Richard Peters & Martin J. Whiting

Behavioral Ecology and Sociobiology

ISSN 0340-5443

Behav Ecol Sociobiol DOI 10.1007/s00265-015-1962-5

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Behav Ecol Sociobiol DOI 10.1007/s00265-015-1962-5

ORIGINAL PAPER

Geographic variation in aggressive signalling behaviour of the Jacky dragon

Marco D. Barquero1,2 & Richard Peters3 & Martin J. Whiting1

Received: 2 March 2015 /Revised: 18 June 2015 /Accepted: 18 June 2015 # Springer-Verlag Berlin Heidelberg 2015

Abstract Signal diversification is often the product of sexual evidence of population-level discrimination. We argue that and/or natural selection and may be accompanied by genetic display variation might be a consequence of behavioural plas- differentiation or simply reflect a plastic response to social and ticity and that, despite difference in genetic structure, mor- environmental variables. We use an agamid endemic to phology and behaviour, this species retains a cohesive com- , the Jacky dragon ( muricatus), to ex- munication system. amine the relationships between population relatedness, mor- phology and signalling behaviour. We also tested whether males are able to discriminate among rivals from different Keywords Amphibolurus . Australia . Lizard . Population populations and whether they respond more aggressively to variation . Visual displays more closely related populations. We studied three popula- tions, two of which belong to the same genetic clade. Individuals from the two most closely related populations communication is a rich and challenging field in large were also more similar in morphology than from the part because of the immense diversity of signals in a wide third, more distant, population. However, all three populations range of taxa. In the case of lizards, visual displays have differed in characteristics of their signalling behaviour includ- gained attention as a highly variable communicative system ing latency to display and the interval between displays. In (Persons et al. 1999). Lizards can signal using colour patches, addition, from all populations showed similar levels body posturing and dynamic visual signals such as tail flicks, of aggression when matched with individuals from the same leg waves and gular or dewlap extensions (Carpenter and or different populations in staged trials and thus did not show Ferguson 1977; Jenssen 1977). Across-species variation is well known, and both natural and sexual selection have been invoked to explain signal diversity in a phylogenetic context Communicated by S. J. Downes (Ord et al. 2002; Stuart-Fox et al. 2007). However, intra- specific variation has received much less attention and rela- Electronic supplementary material The online version of this article (doi:10.1007/s00265-015-1962-5) contains supplementary material, tively few studies have accounted for variation in visual signal which is available to authorized users. structure across populations of the same species (e.g. Ferguson 1971;Jenssen1971; Martins et al. 1998;Lealand * Marco D. Barquero Fleishman 2004; Bloch and Irschick 2006). While we predict [email protected] that wide-ranging and ecologically variable species will show high variation in signal repertoire (Ord et al. 2002), this re- 1 Department of Biological Sciences, Macquarie University, mains to be tested. Furthermore, we know little about signal Sydney, New South Wales 2109, Australia divergence in widely distributed species and whether they 2 Sede del Caribe, Universidad de Costa Rica, Montes de Oca, San respond differently to individuals from geographically dispa- José 2060, Costa Rica rate populations. In some species, a stronger response is elic- 3 Department of Ecology, Environment & Evolution, La Trobe ited from individuals in a receiver’s neighbourhood compared University, Bundoora, Victoria 3086, Australia to more distant, less closely related individuals (Bensch et al. Author's personal copy

Behav Ecol Sociobiol

1998; Dunbrack and Clarke 2003). This may be because they morphology used to produce visual signals differs among pop- constitute less of a threat, possibly as a result of divergence. ulations of the same species, then a concordant pattern of The signalling environment can vary dramatically for variation in the signalling behaviour is predicted. For instance, widely ranging species as a result of habitat structure, envi- if the tail of an animal is used to communicate with conspe- ronmental noise and predation risk, such that differences in cifics and tail length varies among populations, then some visual signals among populations could be a result of local properties of the signal, such as duration and frequency, could adaptation (Podos 2001). However, differences in signalling also be divergent (Barnard 1991; Young et al. 1994). behaviour across the range of a species could also emerge as a However, variation in signalling behaviour is not always ex- result of differences in female preferences during sexual se- plained by variation in morphology (Ferguson 1971; Irwin lection (Uy and Borgia 2000) or through a non-adaptive pro- et al. 2008). Therefore, when comparing populations of the cess such as genetic drift (Hill 1994). Whether a trait is the same species, it is important to consider how variations in result of genetic divergence is of key importance in under- relatedness, morphology and signalling behaviour are related. standing how signals evolve. For example, if signal expres- Figure 1 shows the outcome and associated explanation of the sion is not selected for and it is only the result of genetic geographic variation in signalling behaviour when morpholo- differences among populations of the same species, then dis- gy and relatedness are considered, but not environmental persing animals would not be as constrained by the conditions factors. present at different habitats to perform their visual displays. At Here, we test whether variation in morphology and signal- the same time, if the variation in genetic structure and signal ling behaviour among populations of the Jacky dragon repertoire is high across the range of a species, then dispersing (Amphibolurus muricatus) correlates with their genetic differ- animals could face problems conveying a message to local entiation. We predicted that greater divergence in genetic individuals since signals might not be recognized. Therefore, structure between populations should produce the same effect despite the opportunity to display freely under different envi- in morphology and signalling behaviour. In light of this vari- ronmental conditions, reproductive isolation could arise if ation, we also asked whether individuals have population- populations generate different signals and species recognition specific responses and predicted that they would show stron- cues are incongruent (Bensch et al. 1998; Leal and Fleishman ger (more aggressive) visual displays to individuals from their 2004).