Craig Ivanyi’s scientific contributions

Most visitors to the Arizona-Sonora Desert Museum (ASDM) are fascinated by the large spiny-tailed iguanas that inhabit the museum grounds. Basking on the artificial rock outcrops, they are as charismatic as the bighorn sheep and their head-bobbing displays impress even the most herpeto-phobic people. Spiny-tailed iguanas are large, omnivorous lizards in the genus Ctenosaura, which contains 14 species that collectively range from Mexico to Panama, including Baja California and various offshore islands in the eastern Pacific, western Caribbean and Gulf of California (Grismer 2002). Their origin as a "wild" population on the Desert Museum grounds is quite intriguing. In the mid-1970's, ASDM staff released at least one pair of individuals on the grounds. It is unknown if other individuals were released or escaped since then. Without management by ASDM staff, these individuals have propagated freely and maintain a current population of 25-40 animals. The current staff at the Desert Museum, aware of the potential dangers of invasive species, has been researching the introduced population for the last 8 years. Although the lizards maintain a healthy population on the ASDM grounds, there is no evidence that they have spread into the surrounding Tucson Mountains. The Museum grounds may provide habitat and resources (abundant water and food) not available in the surrounding desert to this mostly warm-climate genus of lizards. Perhaps most critical to the lizard's survival on the ASDM grounds are the deep cavities within the artificial rockwork and buildings that the lizards may use to overwinter; these cavities maintain much warmer temperatures throughout the winter than would be available naturally. The spread of introduced Ctenosaura in Florida (Krysko et al. 2003) is probably a result of the more favorable climate there. For this study, we used molecular methods (DNA typing) to investigate further the origins of the ASDM spiny-tailed iguanas. In particular, we see this as a case study for how invasive species might establish and maintain a population from only a few original individuals. Invasive species are of growing interest to conservation biologists because of their potential to extirpate native species. Although many cases have been documented, biological attributes that give a species the potential to become invasive are poorly understood (Marchetti et al. 2004). It is proposed that invasives are commonly generalists that can easily adapt to new environments (Hänfling and Kollmann 2002). From a molecular standpoint, it might be expected that a species with the potential to become invasive would come from a population with very high genetic diversity, thus increasing the chance for an individual to have the genetic make-up to survive in the new area (Hänfling and Kollmann 2002; Lee 2002). However, there are typically only a few founders of a new population. Once established, the genetic diversity in the introduced population would remain extremely low as a result of rapid population growth and inbreeding (Patti and Gambi 2001). How invasives survive over time with such a small pool of genetic diversity is intriguing and warrants study.