Relationship between oxidative stress and sexual coloration of lizards depends on thermal habitat

Abstract

Sexual signals serve as an honest indicator of individual quality, reflecting either developmental and/or maintenance costs. A possible underlying physiological mechanism is oxidative stress, which could mediate energy trade-offs between sexual signals and other quality traits. In ectotherms, thermal performance acts as a key indicator of individual quality and influence signal intensity. We investigated how oxidative state is reflected in visual signals of lizards from different thermal habitats. According to our hypothesis, efficient thermoregulation requires different strategies in different thermal environments. In a habitat with predictable temperature changes, animals are less exposed to suboptimal temperature ranges and selection will, therefore, be stronger on the maximum oxidative damage at optimal body temperature. Contrarily, in a habitat with rather stochastic thermal shifts, individuals are often constricted by suboptimal thermal conditions, and oxidative damage can be limiting on a wide temperature range. We used Iberolacerta cyreni and Psammodromus algirus inhabiting stochastic and predictable thermal environments respectively. We examined two aspects of oxidative stress: the level of reactive oxygen metabolites at the preferred temperature (maximal ROM) and the temperature range in which animals produce at least 80% of the maximum level of reactive oxygen metabolites (effective ROM range). In I. cyreni, we found that duller coloration was related to a wider effective ROM range, while expression of coloration in P. algirus was negatively correlated with the maximal ROM. Our results suggest that different thermal constraints affect different aspects of oxidative damage which can indicate individual quality and are, therefore, represented in sexual ornaments.

Longitudinal effects of habitat quality, body condition, and parasites on colour patches of a multiornamented lizard

“…This suggests that the allocation of carotenoids and melanin to yellow and blue patches, respectively, may plastically vary for needs other than signalling during the breeding season (e.g., Brawner et al 2000). Furthermore, the observed changes in the reflectance properties of the blue coloration support previous findings suggesting that this patch can reflect stress levels in this species (Mészáros et al 2019). Contrarily to the yellow and blue patches, no significant effect of the treatment on the orange patch was detected.…”

Integrating behavioural thermoregulatory strategy into the animal personality framework using the common lizard, Zootoca vivipara as a model

“…Smears were fixed and stained with a haematological stain set designed for determination of differential blood cell count (Reag-Quick Panoptic set, Reagens Kft). Parasite intensity was estimated by counting the number of infected red blood cells per 1000 randomly selected red blood cells under the light microscope during three scanning sessions on each smear 103 . The average of the three sessions was used to represent individual parasite infection intensity.…”

A comparative analysis of habitat quality between artificial and natural creeks in the Mediterranean killifish Aphanius fasciatus: Implications for conservation

“…The approach proposed by Hill (1995) involves the study of colour traits that could represent a non‐invasive method to assess the quality of individuals and, therefore, assess the quality of their environment. Sexual ornaments are a product of sexual selection, but they are also dependent on the environment, and thus represent a reliable indicator not only of the physical condition of the bearer, but also of the general status of the environment (Mészáros et al, 2019; Roberts & King, 2019). Sexual ornamental traits, such as coloured skin, feathers, and scales, are extremely sensitive to environmental conditions and reflect the sum of environmental pressures on the animal (Hadfield & Owens, 2006; Roulin, 2016).…”