Document: MIC-3-49-4

Endurance capacity and acclimation in high elevation lizards.

ROBSON, M.A.*

University of Pennsylvania, Philadelphia, PA 19104, USA ¹

Abstract:
The physiological response to changes in pO₂ in reptiles has been ambiguous. Very little is known about the physiological consequences of oxygen concentrations on free-ranging animals. Ambient levels of pO₂ may in part, explain variation in locomotor performance. Further, acclimation to pO₂ levels between populations of a species whose distribution spans a large elevational gradient may be exhibited in whole body physiological responses, i.e., endurance. Previously, I detected significant variation in endurance capacity in Sceloporus graciosus from 2460-m when evaluated across a 2200-m range. In addition, there was no response in S. occidentalis from 1460-m across this same range. Further, when acclimated to lower elevations, S. graciosus demonstrated significantly longer endurance capacities with concurrent significant decreases in hematocrit. The current study was conducted on two populations of S. scalaris in southeastern AZ. High and low elevation populations were sampled from the Chiricahua Mountains (2700-m) and Empire Valley (1375-m), respectively. Initial endurance capacity and hematocrit was determined at the resident elevation. Individuals were reciprocally transplanted at each elevation and maintained for 5 weeks during which endurance capacity was measured weekly. Final hematocrit and resident endurance was again measured at the end of the experiment. Concurrently, samples from each elevation were evaluated for endurance capacity at resident and reciprocal elevations immediately upon capture. Significant differences in endurance capacity existed between populations; however, no differences were detected within a population at reciprocal elevations. Both populations demonstrated significant acclimation to reciprocal elevations after 4 weeks. Interestingly, this response did not persist in high elevation lizards returned to their resident elevation but did in low elevation lizards. Both demonstrated significant decreases in hematocrit.

Keywords: endurance, lizard, acclimation

This abstract is being presented at: 10:30 AM in session:
Oral Session #27: Salamanders, Lizards, and Tortoises.