Influence of incubation temperature on morphology, locomotor performance, and early growth of hatchling wall lizards (Podarcis muralis)

Eggs of wall lizards (Podarcis muralis) were incubated at three temperature s approaching the upper limit of viability for embryonic development in thi s species (26, 29, and 32 degrees C) to assess the influence of temperature on various aspects of hatchling phenotype likely affecting fitness. The th ermal environment affected size and several morphometric characteristics of hatchling lizards. Hatchlings from eggs incubated at 32 degrees C were sma ller (snout-vent length, SVL) than those from 26 and 29 degrees C and had s maller mass residuals (from the regression on SVL) as well as shorter tail, head, and femur relative to SVL. Variation in the level of fluctuating asy mmetry in meristic and morphometric traits associated with incubation tempe ratures was quite high but not clearly consistent with the prediction that environmental stress associated with the highest incubation temperatures mi ght produce the highest level of asymmetry. When tested for locomotor capac ity in trials developed at body temperatures of 32 and 35 degrees C, hatchl ings from the 32 degrees C incubation treatment exhibited the worst perform ance in any aspect considered (burst speed, maximal length, and number of s tops in the complete run). Repeated measures ANCOVAs (with initial egg mass as covariate) of snout-vent length and mass of lizards at days 0 and 20 re vealed significant effects of incubation temperature only for mass, being a gain the hatchlings from eggs incubated at 32 degrees C those exhibiting th e smallest final size. All together, our results evidenced a pervasive effe ct of thermal regime during incubation (and hence of nest site selection) o n hatchling phenotypes. However, incubation temperature does not affect hat chling phenotypes in a continuous way; for most of the analysed traits a cr itical threshold seems to exist between 29 and 32 degrees C, so that hatchl ings incubated at 32 degrees C exhibited major detrimental effects. (C) 200 0 Wiley-Liss, Inc.