Class Year



ectotherms, thermal sensitivity, Herpetology


It is well known that activity, including sprint speed, is highly temperature dependent in ectothermic organisms. Because temperature changes across elevations, the wide elevational range of the lizard Sceloporus malachiticus in Costa Rica is an enigma. We tested thermal sensitivity of sprint speed in S. malachiticus from high (3500m) and low (2200m) elevation populations near Savegre Lodge in San Gerardo de Dota, Costa Rica. To test the hypothesis that lizards from low elevations have narrower thermal envelopes than lizards at high elevations, we conducted temperature controlled sprint trials on noosed lizards from both elevations. Lizards from both populations performed comparably at ambient temperature; however, high elevation lizards were faster at both extremes suggesting phenotypic differences between populations which may be explained by genetic variation or phenotypic plasticity. Such studies are essential to understanding the fundamental processes underlying speciation and adaptation.


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