Enzyme function and polymorphism: A test in two Anolis lizard species

Electrophoretic surveys of two lizard species were used to test hypotheses that relate levels of enzyme variability to enzyme function (single-substrate versus multiple-substrate enzymes, regulatory versus nonregulatory enzymes). Anolis roquet behaviorally regulates its body temperature, but its congener A. gundlachi is passive to variations in the thermal environment. As a result, populations of A. gundlachi probably experience the thermal environment as temporally coarse-grained, whereas populations of A. roquet do not. We therefore predicted that A. gundlachi would exhibit greater enzyme heterozygosity than A. roquet and that different enzyme classes would contribute disproportionately to this interspecific difference. The data show (1) that A. gundlachi does have a higher heterozygosity and (2) that this difference appears to result from high levels of heterozygosity at loci coding for multiple-substrate enzymes. The dichotomy between regulatory and nonregulatory enzymes offers no explanation for the variability in heterozygosity among enzyme loci in these species.E.Z. was supported by a grant from the Natural Sciences and Engineering Council of Canada. The study was accomplished while P.E.H. held a postdoctoral fellowship from the Killam Trust of Dalhousie University and a grant from the Research Development Fund of Dalhousie University. The collection of material was made possible by grants (to P.E.H.) from National Science Foundation (DEB 75-16334), the Explorers Club of New York, Sigma Xi, and the Richmond and Anderson Funds of Harvard University. We thank Dr. D. W. Foltz for his help with the calculations.