Temperature, but Not Available Energy, Affects the Expression of a Sexually Selected Ultraviolet (UV) Colour Trait in Male European Green Lizards

Abstract

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.

Individual quality and nuptial throat colour in male European green lizards

“…Considering that male throat nuptial colouration is developing after hibernation and before the onset of the mating season in our species, the significant year effect is suggestive of a strong environmental component in colour development. Indeed, our manipulative experiment showing the importance of ambient temperature in colour development in L. viridis (Bajer et al ., ), along with our observations of great yearly variation in precipitation and temperature during spring in the three study years, supports this scenario. At any rate, if colour development is affected by environmental conditions, the ability to occupy and defend territories with high thermal quality can also be viewed as an aspect of individual quality, hence the environmental effect further supports our view that the studied colour signals transfer relevant information about their holder.…”

“…Several costs of the expression of sexually selected signals have been shown, including developmental (Baird, ), social (Martin & Forsman, ), physiological (Cox et al ., ) and predatory costs (Stuart‐Fox et al ., ). In a manipulative factorial experiment (Bajer et al ., ), we found that UV colour development before mating season was unaffected by food manipulations (even though body condition was affected) but was significantly influenced by ambient temperature (even though it did not affect body condition). Hence, direct developmental costs are unlikely, but indirect costs are possible due to the need of extended periods of high body temperature, which requires accurate behavioural thermoregulation that comes with many costs (e.g.…”

Effects of energy and thermoregulation time on physiological state and sexual signal in a lizard

“…Production and maintenance of structural colors have been shown to be energetically costly (Megía‐Palma, Martínez, & Merino, ; Prum, ), with both developmental stress and available nutrients influencing coloration in lizards (Olsson et al., ). Additionally, previous studies showed that nuptial throat coloration is condition dependent (Molnár et al., ) and affected by environmental factors (Bajer et al., ) in the study species. Previously, it was found that the development of the throat patch color right after the hibernation was affected by basking time and not by available energy (Bajer et al., ).…”

“…Additionally, previous studies showed that nuptial throat coloration is condition dependent (Molnár et al., ) and affected by environmental factors (Bajer et al., ) in the study species. Previously, it was found that the development of the throat patch color right after the hibernation was affected by basking time and not by available energy (Bajer et al., ). In this study, the lizards were captured after they fully developed their nuptial coloration so in this case we studied the maintenance and not the development costs of the same throat patch.…”

“…UV intensity has been shown to affect success in male–male interactions (Bajer, Molnár, Török, & Herczeg, ) and female mate choice (Bajer, Molnár, Török, & Herczeg, ). Additionally, suboptimal environmental temperature significantly decreased UV color development (Bajer et al., ). Different throat color components act as a condition‐dependent multiple signaling system (Molnár et al., ), conveying information about blood parasite infection (Haemogregarinidae) (Molnár et al., ) and spatial strategies (Molnár, Bajer, Szövényi, Török, & Herczeg, ).…”