When field experiments yield unexpected results: lessons learned from measuring selection in White Sands lizards

Area of Science:

• Evolutionary Biology
• Ecology
• Herpetology

Background:

• Understanding the adaptive significance of phenotypic traits is crucial for evolutionary biology.
• The White Sands ecosystem offers a unique setting to study trait adaptation and natural selection.
• Blanched coloration in White Sands lizards is a recent trait, likely evolved for predator avoidance.

Purpose of the Study:

• To investigate the relationship between coloration and predation susceptibility in White Sands lizards.
• To quantify the effect of substrate-matching phenotypes on survivorship in *Holbrookia maculate*.
• To explore variations in natural selection pressures across spatial and temporal scales.

Main Methods:

• Enclosure experiments were conducted with *Holbrookia maculate* lizards.
• Survivorship was quantified for lizards with substrate-matched versus substrate-mismatched phenotypes.
• Predation rates were analyzed in relation to lizard color, sex, and environmental factors.

Main Results:

• Lizards experienced high rates of predation, but color did not significantly affect survival.
• Predation intensity varied significantly across small spatial and temporal scales.
• A marginally significant interaction between sex and color suggested stronger selection for substrate matching in males.

Conclusions:

• The study highlights the complexity of natural selection in field settings.
• Unexpected results challenge simple hypotheses about trait-based selection.
• Further research is needed to understand the nuanced interplay of factors influencing survival and adaptation.