Many authors hypothesized that coloration and dorsal pattern could be important for reptile thermoregulation, because skin pigmentation causes significant differences in light reflectance and some suggested that melanistic individuals could thermoregulate more efficiently. Podarcis muralis shows a dorsal polymorphism, with three different patterns, so the aim of our work was to test if different dorsal patterns were correlated to different thermal behaviours. We used two complementaryapproaches: a field study of a wild population (63malesand 30 females, ExpA) and an experimental study of heating rates in relation to dark pigmentation (22males and 29females, ExpB). ExpA: all lizards were sexed, measured, photographed, marked with dorsal paintings and released;each time a marked lizard was seen, body temperature (Tb) was measured using an infrared thermometer and air temperature (Ta) was measured con-temporarily with a digital thermometer. ExpB: lizards were kept in terraria and heated pro-gressively, measuring Tband Ta at standard intervals with the same instruments. Data were analysed by means of a mixed model, using Tb as dependent variable, lizard identity as a ran-dom factor to account for repeated measures, dorsal morph (reticulated, striped and mixed), SVL, sex, Taand reproductive period (reproductive: April–June; post-reproductive: July–October) as fixed factors. Both experiments gavethe same results, highlighting the depend-ence of Tb on Ta, but excluding any effect of other predictors. The lack of effects of dorsal patterns is particularly interesting, since it demonstrates that darker colorations do not con-fer any advantage in thermoregulation. This result seems to confirm data collected for other reptiles that underlined the effect of melanism on thermoregulation only in large species.

Back to black: the role of melanin in thermoregulation of polymorphic lizards

SACCHI, ROBERTO;
2013-01-01

Abstract

Many authors hypothesized that coloration and dorsal pattern could be important for reptile thermoregulation, because skin pigmentation causes significant differences in light reflectance and some suggested that melanistic individuals could thermoregulate more efficiently. Podarcis muralis shows a dorsal polymorphism, with three different patterns, so the aim of our work was to test if different dorsal patterns were correlated to different thermal behaviours. We used two complementaryapproaches: a field study of a wild population (63malesand 30 females, ExpA) and an experimental study of heating rates in relation to dark pigmentation (22males and 29females, ExpB). ExpA: all lizards were sexed, measured, photographed, marked with dorsal paintings and released;each time a marked lizard was seen, body temperature (Tb) was measured using an infrared thermometer and air temperature (Ta) was measured con-temporarily with a digital thermometer. ExpB: lizards were kept in terraria and heated pro-gressively, measuring Tband Ta at standard intervals with the same instruments. Data were analysed by means of a mixed model, using Tb as dependent variable, lizard identity as a ran-dom factor to account for repeated measures, dorsal morph (reticulated, striped and mixed), SVL, sex, Taand reproductive period (reproductive: April–June; post-reproductive: July–October) as fixed factors. Both experiments gavethe same results, highlighting the depend-ence of Tb on Ta, but excluding any effect of other predictors. The lack of effects of dorsal patterns is particularly interesting, since it demonstrates that darker colorations do not con-fer any advantage in thermoregulation. This result seems to confirm data collected for other reptiles that underlined the effect of melanism on thermoregulation only in large species.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/760231
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