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Question: What is the basis for geographic variation in microhabitat use in fence lizards?

Hypothesis: Population differences in microhabitat use reflect behavioural plasticity rather than genetic or experiential differences.

Organisms: Western fence lizards (Sceloporus occidentalis).

Field site: Three sites (desert, valley, and mountain) in southern California, USA.

Methods: We compared habitat use by free-ranging lizards in three field populations. We also collected lizards from these three populations and studied their microhabitat use in experimental enclosures at a single field site.

Results: In the wild, lizards chose higher and shadier perches at the hottest (desert) site, lower and sunnier perches at the coolest (mountain) site, and intermediate perches at the thermally intermediate valley site. However, lizards collected from the three source populations did not differ in microhabitat use in experimental enclosures at a common field site, supporting our hypothesis. Microhabitat choice is an important thermoregulatory mechanism in this species.