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Animal communication through colour signals is a central theme in sexual selection. Structural colours can be just as costly and honest signals as pigmentbased colours. Ultraviolet (UV) is a structural colour that can be important both in intrasexual competition and mate choice. However, it is still unknown if a UV signal alone can determine the outcome of male-male fights. European green lizard (Lacerta viridis) males develop a nuptial throat coloration with a strong UV component. Among males differing only in their manipulated UV colour, females prefer males with higher UV. Here, we experimentally decreased the UV coloration of randomly chosen males from otherwise similar male pairs to test the hypothesis that a difference in UV colour alone can affect fight success during male-male competition. Our results fully supported the hypotheses: in almost 90 per cent of the contests the male with reduced UV lost the fight. Our results show that UV can be an important signal, affecting both female mate choice and determining male fight success.

During female mate choice, conspicuous male sexual signals are used to infer male quality and choose the best sire for the offspring. The theory of parasite-mediated sexual selection (Hamilton-Zuk hypothesis) presumes that parasite infection can influence the elaboration of sexual signals: resistant individuals can invest more energy into signal expression and thus advertise their individual quality through signal intensity. By preferring these males, females can provide resistance genes for their offspring. Previous research showed that nuptial throat colour of male European green lizard, Lacerta viridis, plays a role in both inter- and intrasexual selections as a condition-dependent multiple signalling system. The aim of this study was to test the predictions of the Hamilton-Zuk hypothesis on male European green lizards. By blood sampling 30 adult males during the reproductive season, we found members of the Haemogregarinidae family in all but one individual (prevalence = 96%). The infection intensity showed strong negative correlation with the throat and belly colour brightness in line with the predictions of the Hamilton-Zuk hypothesis. In addition, we found other correlations between infection intensity and other fitness-related traits, suggesting that parasite load has a remarkable effect on individual fitness. This study shows that throat patch colour of the European green lizards not only is a multiple signalling system but also possibly acts as an honest sexual signal of health state in accordance with the Hamilton-Zuk hypothesis.

Background Colour signals are widely used in intraspecific communication and often linked to individual fitness. The development of some pigment-based (e.g. carotenoids) colours is often environment-dependent and costly for the signaller, however, for structural colours (e.g. ultraviolet [UV]) this topic is poorly understood, especially in terrestrial ectothermic vertebrates. Methodology/Principal Findings In a factorial experiment, we studied how available energy and time at elevated body temperature affects the annual expression of the nuptial throat colour patch in male European green lizards ( Lacerta viridis ) after hibernation and before mating season. In this species, there is a female preference for males with high throat UV reflectance, and males with high UV reflectance are more likely to win fights. We found that (i) while food shortage decreased lizards' body condition, it did not affect colour development, and (ii) the available time for maintaining high body temperature affected the development of UV colour without affecting body condition or other colour traits. Conclusions/Significance Our results demonstrate that the expression of a sexually selected structural colour signal depends on the time at elevated body temperature affecting physiological performance but not on available energy gained from food per se in an ectothermic vertebrate. We suggest that the effect of high ambient temperature on UV colour in male L. viridis makes it an honest signal, because success in acquiring thermally favourable territories and/or effective behavioural thermoregulation can both be linked to individual quality.

Behaviour is one of the most plastic quantitative traits in animals (West-Eberhard, 2003). 47However, between-individual behavioural variation in the same context and situation became 48 accepted as a valid and biologically important phenomenon lately (Gosling, 2001; Sih et al. 49 2004a Sih et al. 49 , 2004bSmith and Blumstein, 2008;Stamps, 2007;Wilson, 1998). Individual 2014). Behavioural consistency could be seen as a disadvantageous trait, since it constraints 54 plasticity and thus limits the individual behavioural repertoire, which might be maladaptive in 55 variable environments and certain contexts (Bell, 2005(Bell, , 2007 Dzieweczynski and Hebert, 56 2013; Sih et al. 2012Sih et al. , 2004a. Thus, for instance, an individual aggressive towards conspecific 57 competitors remains aggressive in other contexts (e.g. towards predators / during mating) 58 when this behaviour is likely to decrease fitness (e.g. Berning et al. 2012). Hence, one of the 59 most important aims of current evolutionary behavioural ecology is to understand the ultimate 60 and proximate mechanisms that resulted in the emergence of behavioural consistency. 62Estimating individual quality or 'true' fitness is notoriously hard, and thus linking animal 63 personality to individual quality is not straightforward in most possible models. Further, 64 individual quality could mean different things to different researchers, and even proxies of 65 quality might depend on the conceptual framework of the study (Wilson and Nussey, 2010; 66 Bergeron et al. 2011). One possible solution for non-model species is to focus on ecologically 67 4 relevant traits with proven, or at least highly probable, link to fitness. Establishing the 68 relationships between them and personality would be relevant for understanding how 69 behavioural consistency emerges in nature. 71European green lizard (Lacerta viridis) is an excellent candidate for such a study. Males have 72 ultraviolet-blue nuptial throat colouration that is a multiple honest signal and has important 73 roles in both intra-and intersexual selection (Bajer et al. 2010(Bajer et al. , 2011(Bajer et al. , 2012 Molnár et al. 74 2012 Molnár et al. 74 , 2013 Vaclav et al. 2007). Other morphological traits have also been shown to be 75 important determinants of lizards' fitness, like the number and symmetry of femoral pores 76 (Lopez et al 2002) or the size of head (Gvozdik and Van Damme, 2003;Roughgarden, 1974; 77 Vitt, 2000). One can also include traits that are known to be strongly connected to fitness in 78 almost any species, like body size or body condition (Peters 1983;Roff 1992;Stearns 1992 Bajer et al. 2012Bajer et al. , 2011Bajer et al. , 2010 Molnár et al. 2013 Molnár et al. , 2012: (1) 154 brightness: the total reflectance from 320 and 700 nm; (2) UV chroma (relative UV intensity): 155 the percent of reflectance measured in the UV range compared to total reflectance (R 320-156 400 /R 320-700 ); and (3) blue chroma (relative blue intensity): the perc...

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Understanding the background mechanisms affecting the emergence and maintenance of consistent between-individual variation within population in single (animal personality) or across multiple (behavioural syndrome) behaviours has key importance. State-dependence theory suggests that behaviour is ‘anchored’ to individual state (e.g. body condition, gender, age) and behavioural consistency emerges through behavioural-state feedbacks. A number of relevant state variables are labile (e.g. body condition, physiological performance) and expected to be affected by short-term environmental change. Yet, whether short-term environmental shifts affect behavioural consistency during adulthood remains questionable. Here, by employing a full-factorial laboratory experiment, we explored if quantity of food (low vs. high) and time available for thermoregulation (3h vs. 10h per day) had an effect on activity and risk-taking of reproductive adult male European green lizards (Lacerta viridis). We focussed on different components of behavioural variation: (i) strength of behavioural consistency (repeatability for animal personality; between-individual correlation for behavioural syndrome), (ii) behavioural type (individual mean behaviour) and (iii) behavioural predictability (within-individual behavioural variation). Activity was repeatable in all treatments. Risk-taking was repeatable only in the low basking treatments. We found significant between-individual correlation only in the low food × long basking time group. The treatments did not affect behavioural type, but affected behavioural predictability. Activity predictability was higher in the short basking treatment, where it also decreased with size (≈ age). Risk-taking predictability in the short basking treatment increased with size under food limitation, but decreased when food supply was high. We conclude that short-term environmental change can alter various components of behavioural consistency. The effect could be detected in the presence/absence patterns of animal personality and behavioural syndrome and the level of individual behavioural predictability, but not in behavioural type.

Nuptial traits signalling individual quality are common in numerous animal taxa, and play a significant role in sexual selection. Detecting female mate choice based on visual cues is notoriously hard in lizards. Previously, we found that female European green lizards (Lacerta viridis) preferred to associate with males with high ultraviolet (UV) throat reflectance. Here, we investigated if different components of nuptial throat colour of male European green lizards were correlated to other fitness-related traits, and thus could signal male quality. We found that (1) high UV chroma correlates positively with directional asymmetry and shows a negative trend with body condition; (2) blue chroma is not related to any individual traits; and (3) total throat brightness correlates positively with body size and relative head size, and negatively with ectoparasite load. Our results suggest that having high throat UV reflectance is costly for male European green lizards, so probably only high-quality individuals can afford it, while total brightness of the throat colour signals age, relative head size and health status. Hence, throat colour in male European green lizards is a multiple honest signal.