Mechanisms Influencing Countergradient Variation in Prairie Lizards, Sceloporus consobrinus

Countergradient variation (CnGV) in physiological traits exists among populations of broad-ranging ectotherms. Relatively few studies, however, have addressed the underlying biochemical mechanisms that support enhanced growth and development. We aimed to determine whether CnGV in embryonic development occurs in the Prairie Lizard (Sceloporus consobrinus) and to assess possible mechanisms that contribute to differential embryonic development. We investigated differences in embryonic development between two populations of S. consobrinus from different latitudes by tracking metabolic metrics throughout the incubation period. We found metabolic differences between the two populations that were similar to those observed S. undulatus, a previously studied sceloporine lizard that displays CnGV in development, suggesting that embryos from the high latitude population were developing at a faster rate than those from a lower latitude. However, contrary to our original predictions, aerobic metabolic enzyme activity did not differ between populations. Finally, we found some evidence of a trade-off between embryonic developmental rate and mortality as well as between embryonic and hatchling anaerobic enzyme performance. Our results corroborate previously implicated proximate mechanisms of CnGV in developmental rate in a new lineage of sceloporine lizard. In addition, our results show a novel detriment to embryonic survival in the high latitude population, highlighting that we do not yet understand the complexities of the developmental trade-offs experienced across latitudes.