Color morphs of the fire salamander are discriminated at night by conspecifics and predators
P. Aguilar,
G. Pérez i de Lanuza,
H. Martínez‐Gil
et al.
Abstract:The coexistence of multiple discrete color phenotypes (i.e. color polymorphism) has been studied in many diurnal species where environmental light allows most visual systems to chromatically discriminate color morphs. However, there is a large gap in our understanding of the discrimination thresholds and the function color polymorphisms play at night. We collected spectral data from the throats of red‐ and yellow‐morph males in a polymorphic population of the nocturnal amphibian Salamandra salamandra gallaica.… Show more
“…Also, the literature concerning the influence of male mate choice in anurans remains inconclusive, so it is difficult to draw conclusions regarding the influence of sexual selection on the degree of melanism in frogs. The mechanisms that promote color polymorphisms in nocturnal species, such as common frogs, remain poorly explored compared to diurnal species but there is a possible role of sexual selection and/or differential predation pressures on maintaining color morphs in nocturnal species (Aguilar et al 2023).…”
Variations in melanin-based pigmentation patterns are frequent evolutionary adaptations in vertebrates and allow the study of phenotypic diversity across populations as well as individual recognition. Age-related changes in such pigmentation patterns have been demonstrated for several species but remain rarely explored in adult amphibians. For the wide-ranging European common frog (Rana temporaria) dorsal melanism was discussed in the context of UV protection at high altitude or as thermal adaptation at high latitude, yet patterns remain unquantified across most of its range or in terms of individual variation over time. We investigated dorsal pigmentation patterns in a wild population of R. temporaria in a lowland site in England which was the focus of a 7 year high-intensity mark recapture programme. We collected dorsal photographs using phone cameras and analysed pigmentation patterns using visual classifications and ImageJ image processing software. Pigmentation was highly variable between individuals but overall: (i) the number of melanin-based spots was largely stable or decreased over time as enlarging spots sometimes merged but never disappeared; (ii) the total melanin-based pigmented area increased significantly over time on average, albeit not for all individuals; and (iii) pigmentation was similar in males compared to females although the darkest individuals tended to be males. Our analysis reveals important patterns in pigmentation change and stability in this widespread species but the mechanisms and specific drivers remain unknown.
“…Also, the literature concerning the influence of male mate choice in anurans remains inconclusive, so it is difficult to draw conclusions regarding the influence of sexual selection on the degree of melanism in frogs. The mechanisms that promote color polymorphisms in nocturnal species, such as common frogs, remain poorly explored compared to diurnal species but there is a possible role of sexual selection and/or differential predation pressures on maintaining color morphs in nocturnal species (Aguilar et al 2023).…”
Variations in melanin-based pigmentation patterns are frequent evolutionary adaptations in vertebrates and allow the study of phenotypic diversity across populations as well as individual recognition. Age-related changes in such pigmentation patterns have been demonstrated for several species but remain rarely explored in adult amphibians. For the wide-ranging European common frog (Rana temporaria) dorsal melanism was discussed in the context of UV protection at high altitude or as thermal adaptation at high latitude, yet patterns remain unquantified across most of its range or in terms of individual variation over time. We investigated dorsal pigmentation patterns in a wild population of R. temporaria in a lowland site in England which was the focus of a 7 year high-intensity mark recapture programme. We collected dorsal photographs using phone cameras and analysed pigmentation patterns using visual classifications and ImageJ image processing software. Pigmentation was highly variable between individuals but overall: (i) the number of melanin-based spots was largely stable or decreased over time as enlarging spots sometimes merged but never disappeared; (ii) the total melanin-based pigmented area increased significantly over time on average, albeit not for all individuals; and (iii) pigmentation was similar in males compared to females although the darkest individuals tended to be males. Our analysis reveals important patterns in pigmentation change and stability in this widespread species but the mechanisms and specific drivers remain unknown.
“…Besides genetic and disease-related causes, oxidative stress can be caused by environmental factors and induced by several mechanisms, including pollutants, different forms of radiation, nutrition, and other environmental interactions [25]. Oxidative stress markers include, for example protein post-translational modifications (PTMs) such as 3-nitrotyrosine (3-NT) [26,27] and carbonylation [28][29][30]. Some evidence exists for cross-talk between protective molecular chaperone activity and oxidative stress markers, where HSPs and HSP-like molecules play a role in protection against oxidative damage [31][32][33] and this evidence extends to natural populations (e.g., HSP70, HSP60, HSP90, HSC70, GRP75) [34].…”
Better understanding how organisms respond to their abiotic environment, especially at the biochemical level, is critical in predicting population trajectories under climate change. In this study, we measured constitutive stress biomarkers and protein post-translational modifications associated with oxidative stress in Gallotia galloti, an insular lizard species inhabiting highly heterogeneous environments on Tenerife. Tenerife is a small volcanic island in a relatively isolated archipelago off the West coast of Africa. We found that expression of GRP94, a molecular chaperone protein, and levels of protein carbonylation, a marker of cellular stress, change across different environments, depending on solar radiation-related variables and topology. Here, we report in a wild animal population, cross-talk between the baseline levels of the heat shock protein-like GRP94 and oxidative damage (protein carbonylation), which are influenced by a range of available temperatures, quantified through modelled operative temperature. This suggests a dynamic trade-off between cellular homeostasis and oxidative damage in lizards adapted to this thermally and topologically heterogeneous environment.
The study of colour, including physical properties and patterns, is an essential step in comprehensively understanding the role, evolution and diversification of this trait involved in functions like survival, performance, reproductive success and communication. While quantitative studies on colour have primarily focused on colour attributes, such as hue or brightness, the quantitative assessment of how colours are distributed across an organism's body (i.e. pattern) has received less attention despite its high functionality irrespective and together with colour. This gap is particularly noticeable in amphibians, especially in highly polymorphic, continuously variable species. In this study, we use the urodele Salamandra salamandra as a study model to apply an analytical approach for extracting and quantifying colour proportions and patterns variation using the recently developed R packages patternize and recolorize to precisely describe and compare colour distribution at both taxonomic and habitat levels. We first assessed the potential application of this workflow in taxonomic studies by examining its accuracy and sensitivity in differentiating morphs, using S. s. bernardezi and S. s. gallaica subspecies. Subsequently, we applied the same analytical approach to compare colour and colour pattern shifts among population of S. s. bernardezi within an urban–forest system. Our results demonstrated that this methodological workflow effectively detects differences in colour patterns at the taxonomic and habitat levels, confirming its utility in different fields, from systematics to eco‐evolutionary studies. Furthermore, our results revealed an increased prevalence of melanistic colouration and a less homogeneous colour pattern within urban settings, contributing to the limited number of studies about amphibian colouration in anthropic habitats. We outline and discuss alternative hypotheses to explain these patterns, although further investigation is necessary to address several new questions that arise from our results.
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