The relative importance of body size and UV coloration in influencing male-male competition in a lacertid lizard

Abstract

Communication via color signals is common in natural systems. Ultraviolet (UV)-blue patches located on the outer-ventral scales of some Lacertid lizards are thought to be involved in male-male competition. However, the mechanisms that maintain their honesty remain unknown. Here, we use the common wall lizard Podarcis muralis to test whether the lateral UV-blue spots are conventional signals, the honesty of which is guaranteed by receiver-dependent costs, and discuss their potential role as an amplifier of body size. We first described the morphology and reflectance properties of lateral UV-blue spots in common wall lizards and investigated how they influence malemale competition. Spot size and number, UV chroma, and conspicuousness (calculated using vision models) were significantly greater in adult males relative to adult females and adult males relative to juveniles. Total spot area (and not spot number) of adult males was positively correlated with body size. We conducted staged competition encounters between focal males and smaller or larger rivals with control or manipulated spots. Spots were enlarged in small rivals and reduced in large rivals to disrupt the phenotypic correlation between spot area and body size. Aggressiveness and dominance were positively influenced by body size in control encounters. Spot manipulations resulted in greater submission and less aggressiveness in focal males. These results contradict the predictions associated with conventional signals and amplifiers, but suggest that spots contributed to opponent evaluation during shortdistance encounters between competing males.

Does reproductive mode affect sexually-selected coloration? Evaluating UV–blue spots in parthenogenetic and bisexual lizards of the genusDarevskia

“…We have confirmed sexual dimorphism in both quantitative and chromatic parameters of the UV–blue traits in Darevskia lizards. Our results are consistent with other studies on lacertids showing that the blue/UV–blue lateral spots occupy larger area and/or are more numerous in males than in females, for example, Psammodromus algirus ( Carretero 2002 ), G. galloti ( Molina-Borja et al 2006 ), T. lepidus ( Font et al 2009 ), P. muralis ( Names et al 2019 ). Significant sex × species interactions in the LMs confirm that sexual dimorphism in OVS (UV–blue area, spot count, and chromatic parameters) varies considerably across the species ( Figure 6 ).…”

“…The same was not proven for the shoulder spots, however, this could have been caused by small sample sizes in this particular subset of data. Despite the high interspecific variability, the GLS model predicts a general tendency of OVS UV–blue area to grow with body size in males, rather than females ( Figure 5 ), which is also consistent with observations in Podarcis lizards ( Names et al 2019 ).…”

“…A number of lacertid species have UV–blue spots on their throats, shoulders, flanks, or bellies, which are more prominent in males than females (e.g., Gallotia galloti ( Molina-Borja et al 2006 ), Timon lepidus ( Font et al 2009 ), Podarcis sp. ( Pérez I de Lanuza and Font 2010 ; Pérez I de Lanuza et al 2014 ; Names et al 2019 )). The UV coloration in males also positively correlates with their fighting ability or mating success, as was reported, for example, in the European green lizard, Lacerta viridis ( Bajer et al 2011 ; Molnár et al 2012 ), sand lizard, L. agilis ( Olsson et al 2011 ), Schreiber’s green lizard, L. schreiberi ( Martín and López 2009 ), or common wall lizard, Podarcis muralis ( Pérez I de Lanuza et al 2014 ; MacGregor et al 2017 ).…”

Male ultraviolet reflectance and female mating history influence female mate choice and male mating success in a polyandrous lizard

“…Andersson, Örnborg, & Andersson, 1998;Siebeck, 2004;Ries et al, 2008;Badiane, Carazo, & Font, 2018) and have a visual system sensitive to UV light (Bowmaker, 2008;Cronin & Bok, 2016). We have now good evidence that UV coloration can be sexually dichromatic (Hunt et al, 1998;Names et al, 2019) and act as honest, condition-dependent Female mate choice for UV reflectance 4 indicator of male quality (e.g. Keyser & Hill, 1999, 2000Griggio, Zanollo, & Hoi, 2010;Pérez i de Lanuza, Carazo & Font, 2014).…”

“…UV coloration in lizards seems to function as honest indicator of male quality (e.g. Whiting et al, 2006;Molnár et al, 2012;Pérez i de Lanuza, Carazo, & Font, 2014) and has been shown to influence social aggressiveness, dominance, and contest outcome during male-male competition (Stapley & Whiting, 2006;Bajer et al, 2011;Martin et al, 2016;Names et al, 2019). For example, in European green lizards Lacerta viridis, UV coloration signals male quality (Molnár et al, 2012(Molnár et al, , 2013, determines male fighting success (Bajer et al, 2011), and predicts female mate choice (Bajer et al, 2010).…”