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Environmental Gradients in Lizard Colouration
Lekshmi B Sreelatha1,2,3, Pedro Tarroso1,2,3, Ossi Nokelainen4,5
1CIBIO-InBIO Associate Laboratory, Research Centre in Biodiversity and Genetic Resources University of Porto Vairão Portugal.
Ecology and Evolution
|March 3, 2025
Summary
Animal colouration adapts to environmental pressures. For Lusitanian wall lizards, humidity influences dorsal brightness, while colder climates correlate with larger, darker animals, supporting Gloger's and Bergmann's hypotheses.
Area of Science:
- Ecology
- Evolutionary Biology
- Herpetology
Background:
- Environmental pressures significantly influence animal colouration, driving adaptation to local conditions.
- The precise impact of climatic gradients on species' colour variation across their distribution is not fully understood.
- Understanding these relationships is crucial for predicting species' responses to environmental change.
Purpose of the Study:
- To investigate spatial variation in the dorsal colouration of Lusitanian wall lizards (Podarcis lusitanicus) in response to environmental gradients.
- To test hypotheses regarding the influence of climate on colouration, including Gloger's, thermal melanism, photoprotection, and Bergmann's hypotheses.
- To elucidate direct and indirect pathways (mediated by body mass) linking environmental variables to lizard colouration.
Main Methods:
- Multispectral photography was used to quantify dorsal colour brightness (lightness) in 463 Lusitanian wall lizards from 21 locations.
- Piecewise structural equation modelling was employed to analyze relationships between environmental variables and lizard lightness, considering body mass.
- Predictions from Gloger's, thermal melanism, photoprotection, and Bergmann's hypotheses were simultaneously tested.
Main Results:
- Lizard lightness significantly correlated with humidity, supporting Gloger's hypothesis, but not with solar radiation intensity (photoprotection hypothesis).
- No direct relationship was found between temperature and lightness (thermal melanism), but an indirect effect was detected via body size.
- Lizards in colder regions exhibited larger body size and darker dorsal colouration, consistent with Bergmann's hypothesis.
Conclusions:
- Climatic factors, particularly humidity and temperature (indirectly through body size), are key drivers of dorsal colour evolution in Lusitanian wall lizards.
- The findings highlight the complex interplay of environmental pressures and evolutionary adaptations in shaping animal colouration.
- Further experimental research is needed to confirm the causal mechanisms behind climate-driven colour variation in diverse environments.
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