Saving Water to Survive: Alternative Water Loss Strategies Could Explain Color Polymorphism Maintenance in a Lacertid...

Area of Science:

• Ecology
• Evolutionary Biology
• Herpetology

Background:

• Color polymorphism is common in lizards, but the underlying physiological trade-offs are not fully understood.
• The common wall lizard (Podarcis muralis) exhibits distinct color morphs, including red, white, and yellow males.

Purpose of the Study:

• To investigate a potential trade-off between hydroregulation and thermoregulation in different color morphs of male Podarcis muralis.
• To test the hypothesis that red males prioritize water balance over precise temperature control, unlike white and yellow morphs.

Main Methods:

• Experimentally measured evaporative water loss (EWL) rates in 36 male lizards (12 per morph).
• Tested lizards at a high temperature (37°C) under both dry and humid air conditions.
• Controlled for behavioral adjustments and body size differences.

Main Results:

• The red morph consistently showed significantly higher EWL rates compared to white and yellow morphs.
• No significant differences in EWL were found between white and yellow morphs.
• Observed EWL differences suggest physiological mechanisms for water conservation in white and yellow lizards.

Conclusions:

• Findings support the hypothesis of a thermo-hydroregulation trade-off in Podarcis muralis color morphs.
• The red morph's higher EWL may be advantageous in cooler, wetter environments, while white/yellow morphs are better adapted for water conservation.
• This trade-off, along with others (aggression vs. survival), likely maintains stable polymorphism in the species.