Geographic Variation in Aggressive Signalling Behaviour of the Jacky Dragon
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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 1 23 Your article is protected by copyright and all rights are held exclusively by Springer- Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 1 23 Author's personal copy 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 lizard endemic to phology and behaviour, this species retains a cohesive com- Australia, the Jacky dragon (Amphibolurus 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 Animal communication is a rich and challenging field in large were also more similar in morphology than lizards 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, animals 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). own population. This should manifest itself in latency to dis- Visual signals may also be constrained by morphological play and the frequency of their signals. Our rationale is that traits of the individuals in a population (Podos 2001). If the animals will display less aggressively to signals with fewer Fig. 1 Molecular, morphological and signalling behaviour variation when populations of the same species are compared. Variation, when present, can be seen as genotype (or phenotype or behaviour type) 1 in population A, genotype 2 in population B and so on. A potential explanation of the variation in signalling behaviour as a function of molecular and morphological variation is included Author's personal copy Behav Ecol Sociobiol familiar components than they would to familiar signals (al- henceforth referred to as Yarratt, Royal and Cann River, re- though see Dunbrack and Clarke 2003). spectively. Animals from two populations, Yarratt and Royal, are members of the same genetic clade, whereas lizards from Cann River are genetically more distant (see below) (Pepper Methods et al. 2014). Ten to fifteen males were collected from each population and transported to Macquarie University, where Study animal they were housed individually in tubs (70L×49W×30H cm) inside a room maintained at 25 °C and a 12-h light-dark cycle. Jacky dragons are a good model system because they are Individuals were kept in these indoor tubs for 3–4 weeks as a widely ranging and relatively abundant (Cogger 2000) and quarantine period before being moved to outdoor pens. The their signalling behaviour has been described in detail outdoorenclosures(180L×180W×88H cm) were made from (Carpenter et al. 1970; Peters and Ord 2003; Watt and Joss metal