Longterm effects of incubation temperatures on the morphology and locomotor performance of hatchling lizards (Bassiana duperreyi, Scincidae)

Abstract

The phenotypes of hatchling reptiles are known to be affected by the thermal environments they experience during incubation, but the evolutionary and ecological significance of this phenotypic plasticity remains unclear. Crucial issues include: (i) the magnitude of effects elicited by thermal regimes in natural nests (as opposed to constant-temperature incubation); (ii) the persistence of these effects during ontogeny; and (iii) the consistency of these effects across different test conditions (does the thermal regime during embryogenesis simply shift the hatchling's thermal optimum for performance, or actually modify overall performance ability regardless of temperature?). We examined these questions by incubating eggs of scincid lizards (Bassiana duperreyi) from montane southeastern Australia, under two fluctuating-temperature regimes that simulated ‘cold’ and ‘hot’ natural nests. These thermal regimes substantially modified hatchling morphology (mass, body length, tail length, and the relationship between these variables), locomotor performance (running speeds over distances of 25 cm and lm), anti-predator ‘tactics’ and survival rates. The differences in locomotor performance persisted throughout the 20 weeks of our experiment. Lizards that emerged after ‘hot’ incubation were faster runners than their ‘cold’-incubated siblings under all thermal conditions that we tested. Thus, incubation temperatures modified overall locomotor ability, with only a minor effect on the set-point for optimum performance. The magnitude, persistence and consistency of these incubation-induced phenotypic modifications suggest that they may play an important role in evolutionary and ecological processes within lizard populations.