Melanin-based colouration as a potential indicator of male quality in the lizard Zootoca vivipara (Squamata: Lacertidae)

Abstract

In many animals, aspects of colouration are hypothesized to convey information on the body condition or quality of individuals. This idea has been tested primarily for the carotenoid-based component of body colouration. The significance of other pigments in this context has received far less attention. In the common lizard, Zootoca vivipara, the degree of black patterning on the ventrum and throats is sexually dimorphic and varies considerably among individuals. In this study, we examine whether this melanin-based component of body colouration may reflect individual differences in quality (SVL, condition, immune response). We find that males (but not females) with a higher degree of ventral patterning mount a stronger phytohcmagglutinin-induced immune response. The amount of black patterning does not correlate with body size, body condition, aspects of dorsal colouration or parasite load. We conclude that in male Zootoca vivipara, melanin-based ventral colouration may signal an aspect of immune capacity to sexual rivals or potential partners.

Dorsal pattern polymorphism in female Iberian wall lizards: differences in morphology, dorsal coloration, immune response, and reproductive investment

“…Nevertheless, we did not detect differences in immune response between female dorsal morphs, nor correlations between immune response and melanin-based coloration. This is in sharp contrast to the work of Vroonen et al (2013) where male, but not female, Z. vivipara with more melanic ventral coloration mounted a stronger PHA-induced immune response. However, we did not examine this relationship in males and the black ventral patterning in P. hispanicus is very scarce, with just a few small black dots localized in the gular or the ventrolateral areas (Salvador & Carretero, 2014).…”

“…Because darker reptiles have several thermoregulation advantages (Majerus, 1998;Bittner et al, 2002), we can hypothesize that thermoregulation constraints imposed by a small body size (i.e. low thermal inertia, fast heating rates coupled with fast cooling rates; Carrascal et al, 1992;Mart ın & L opez, 2003;Gabirot et al, 2013b) may be, at least partially, responsible for the darker hatchling dorsal coloration in P. hispanicus and other lacertids such Z. vivipara (Vroonen et al, 2013). However, we cannot dismiss the possible role of crypsis in hatchlings and striped females because it was not the focus of the present study.…”

“…However, we use the terms brownish and yellowish coloration because pheomelanin production in lizards has not yet been confirmed. On the other hand, we assume that patches of black coloration are produced by melanin, in accordance with most research on lizards (Morrison, Rand & Frost‐Mason, ; Rosenblum et al ., ; Sacchi et al ., ; Vroonen et al ., ). Both striped and reticulated‐blotched P. hispanicus show dorsal patterns characterized by three distinct colour categories: the first corresponding to the darkest part of the pattern (black), and the yellowish coloration, usually present in minor proportion around the striped or blotched area, and the darker brownish coloration, which is clearly recognizable in the most central part of the back.…”

“…However, this relationship has rarely been explored in lizards. Vroonen, Vervust & Van Damme () reported that melanin pigments signal aspects of immune capacity in male common lizards Z. vivipara . Studies of differences in immune response between dorsal morphs of female Anolis sagrei have yielded contradicting results (Calsbeek et al ., ; Cox & Calsbeek, ).…”

Multiple behavioral contexts of a melanized tail display in a desert lizard

“…In general, melanin is an important pigment molecule in lizard ecology and evolution, and there could exist links between melanin and other organismal traits that we did not explicitly quantify. For example, in lacertid lizards more melanistic coloration is linked to greater immune responses (Baeckens & Van Damme, ; Vroonen, Vervust, & Van Damme, ), suggesting that male quality might be linked to the density of melanistic coloration. Rapid shifts in body color through pigment deposition into melanosomes can often occur during social interactions, where socially dominant green anoles ( Anolis carolinensis ) exhibit lighter dorsal colorations and socially subordinate lizards exhibit darker dorsal colorations (Greenberg & Crews, ).…”