The New World lizard genus, Sceloporus, is the most speciose with the exception of Anolis. Nearly 70 species of Sceloporus lizards occur throughout most of the United States, Mexico, and Central America as far as Panama. The greatest species diversity occurs in Mexico. Most species of Sceloporus are small to medium-sized, and exhibit a variety of ecological positions and life-history strategies. Most species exhibit an oviparous reproductive mode, but viviparity has evolved, independently, at least three times within the genus. The ecological and physiological diversity exhibited by Sceloporus lends this species to be tractable as an organism for studies in comparative biology. This genus has been investigated in studies examining life-history ecology, territoriality, mate selection, thermoregulation, feeding and growth, population genetics, performance physiology, activity metabolism, reproductive anatomy, and endocrine physiology. Sceloporus show a diversity of physiological responses to environmental cues. For instance, different species exhibit different patterns of spermatogenesis associated with female reproductive mode. Oviparous species may initiate spermatocytogenesis in late-summer (e.g., S. undulatus and S. woodi) or in spring (e.g., S. virgatus).

                              
Katie and Alana take measurements on the study site.         Alana and Tim collect data from a lizard in the field.

I am currently conducting field studies on a population of Sceloporus undulatus hyacinthinus at the Raystown Field Station in central Pennsylvania (Huntingdon Co.). At present, four Juniata College students assist me with these studies. During the summer of 1998, Amanda Jane "A.J." Maurer served as my research assistant. A.J. did a wonderful job in leading many aspects of this study and will be presenting data from this work at several meetings this spring and summer. My students and I are evaluating the population size, age structure, longevity, territoriality, and thermoregulatory biology of these lizards. Our study site is 26,000 square metres, and consists predominately of an exposed shale barren and adjacent ridge. Nearly 1,000 animals are individually marked (as of Fall 2001) and we are collecting movement and growth data based on recapture of these lizards. Alana Malar and Tim Lonesky served as summer assistants for 1999. Alana returned for another field season before her senior year. She was joined by Dina Leslie for activities during the summer of 2000. An active spring saw many recaptures of young lizards marked during the fall of 1999. During the summer of 2001, Suzanne Krance served as

In addition to field studies on life-history ecology, I am conducting laboratory-based investigations on the effects of environmental contaminants on reproductive development in Sceloporus embryos. These studies are designed to ellucidate the effects of pesticide exposure on the developing gonads, reproductive tract, and endocrine system.

Below is an animated montage representing several Sceloporus species with which I have conducted research, including S. jarrovi (a viviparous, montane species from Arizona), S. undulatus, S. virgatus, and S. woodi (a species endemic to Florida long-leaf pine/turkey oak scrub habitat).