Elevational patterns of sexual size dimorphism in a Mediterranean lizard

Area of Science:

• * Ecology and Evolutionary Biology
• * Herpetology
• * Sexual Selection and Dimorphism

Background:

• * Sexual size dimorphism (SSD) is a common phenomenon in lizards, with variations attributed to intrasexual and fecundity selection pressures.
• * Lizards serve as a model organism for studying SSD due to their diverse dimorphic patterns (monomorphism, male-biased, or female-biased).
• * Previous research on *Psammodromus algirus* suggests a decrease in sexual selection and an increase in fecundity selection with increasing elevation.

Purpose of the Study:

• * To investigate elevational variations in SSD within the Mediterranean lizard *Psammodromus algirus* along a 2,200 m gradient.
• * To test the hypothesis that male-biased SSD increases at low elevations and female-biased SSD increases at high altitudes.
• * To explore the role of age structure in mediating elevational patterns of SSD.

Main Methods:

• * Field study utilizing an elevational gradient (2,200 m) to collect data on *Psammodromus algirus*.
• * Measurement of body size and age structure for both male and female lizards across different altitudes.
• * Statistical analysis to determine SSD patterns and their correlation with elevation and age structure.

Main Results:

• * Both male and female *Psammodromus algirus* exhibited increased body size with ascending elevation.
• * Female-biased SSD was observed to increase with elevation, with males only being larger at the lowest elevation.
• * Elevational differences in SSD were linked to variations in age structure, with females generally older except at the lowest altitude.

Conclusions:

• * Elevational gradients significantly influence SSD in *Psammodromus algirus*, primarily driven by changes in age structure rather than direct sexual selection pressures.
• * Post-maturational growth in this species, combined with sex-specific age differences, provides a plausible explanation for the observed elevational SSD patterns.
• * Age structure should be considered a critical factor when interpreting SSD variations in species with indeterminate growth.