Reflectance of sexually dichromatic UV-blue patches varies during the breeding season and between two subspecies ofGallotia galloti(Squamata: Lacertidae)

Abstract

Body coloration is sexually dimorphic in many vertebrate species, including lizards, in which males are often more conspicuous than females. A detailed analysis of the relative size of coloured patches and their reflectance, including the ultraviolet (UV) range, has rarely been performed. In the present work we quantified sexual dimorphism in body traits and surface area of all lateral patches from adult females and males of two subspecies of Gallotia galloti (G. g. galloti and G. g. eisentrauti). We also analysed the magnitude of sexual dichromatism in the UV-visible reflectance of such patches and the changes in patch size and brightness during the reproductive season (April-July). Males had significantly larger patch areas (relative to their snout-vent length) and higher brightness (mainly in the UV-blue range) than did females in both subspecies. The comparison of relative patch areas among months did not reach statistical significance. However, patch brightness significantly changed during the breeding season: that of the UV-blue (300-495 nm) range from lizards of the two subspecies was significantly larger in June than in April, while brightness in the 495-700 nm range in G. g. galloti was larger in May, June, and July than in April. A different pattern of dichromatism was also detected in the two populations, with G. g. eisentrauti being more sexually dichromatic than G. g. galloti. We discuss the results in terms of possible evolutionary causes for the sexual dichromatism related to different ecological characteristics of the habitats where each subspecies live.

Interpopulational and seasonal variation in the chemical signals of the lizardGallotia galloti

“…These lizards inhabit different islands of the Canary Achipelago: Tenerife Island ( G. g. eisentrauti and G. g. galloti ), La Palma Island ( G. g. palmae ), and the small islets of Roque de Anaga ( G. g. insulanagae ). In addition, while G. g. eisentrauti and G. g. palmae inhabit cloudy and wet densely vegetated forest areas in northern Tenerife and La Palma respectively, G. g. galloti lives in dry and sunny semidesert areas in the south and the center of Tenerife ( Thorpe & Brown, 1989 ; Bohórquez-Alonso & Molina-Borja, 2014 ). Hence, the divergent ecological conditions of each area might modulate the expression of chemical signals, as it has been described for visual ornaments ( Thorpe & Brown, 1989 ).…”

“…It has been hypothesized that these two compounds might have protective properties under different environmental conditions; cholesterol might protect semiochemicals in dry conditions and vitamin E in wet environments ( Escobar et al, 2003 ; Weldon, Flachsbarth & Schulz, 2008 ; Martín & López, 2014 ). Since the environment varies considerably among subspecies ( Thorpe & Brown, 1989 ; Bohórquez-Alonso & Molina-Borja, 2014 ), this could translate into different abundances of both compounds. Moreover, as this lizard species is active during the whole year, we also examined whether the femoral gland secretions differed between the reproductive and the non-reproductive seasons.…”

Better to be resident, larger or coloured? Experimental analysis on intraspecific aggression in the ruin lizard

“…No evidence of similar patterns are still available for the ruin lizard, thus further studies are needed to investigate the real role of the species polychromatism (Corti et al ., ). Interestingly, in other territorial not polymorphic species, it has been found that, for instance, chromatic patches may function as status signalling badges of aggressiveness, fighting ability or dominance in males (Bohórquez‐Alonso & Molina‐Borja, ). In addition, it has been suggested a possible role of testosterone as modulating factor (i.e.…”

“…Colour in lizards is an important pattern in sexual recognition and both intra‐ and intersexual competition (Bohórquez‐Alonso & Molina‐Borja, ; Klomp et al ., ). Notably, brilliant colours of the back, throat and vent may determine the fighting outcome (Klomp et al ., ) by revealing male's quality and fighting ability to the opponent.…”

“…Notably, brilliant colours of the back, throat and vent may determine the fighting outcome (Klomp et al ., ) by revealing male's quality and fighting ability to the opponent. Furthermore, it has been demonstrated that blue–green colours visible in the UV spectrum still signal healthy, reproductive status (Bajer et al ., ) and dominance status of the animal (Anderholm et al ., ; Whiting et al ., ; Bohórquez‐Alonso & Molina‐Borja, ). This may arise important as determinant during intraspecific aggressions, especially in species keeping condition‐dependent colourations.…”