Recent studies on invasive species have led to the development of an apparent paradox when trying to explain how populations succeed after experiencing genetic bottlenecks in their new environments. Many introduced populations retain genetic diversity from multiple introduction events, but others that resulted from a single introduction event are expected to have low genetic diversity and low evolutionary potential. Introduced Black Spiny-Tailed Iguanas (Ctenosaura similis) on a barrier island (Keewaydin Island [KI]) in subtropical Florida are thought to be the result of a single introduction of a small founder group, although this population has expanded significantly since its founding in 1995. We investigated the presence of this genetic paradox by determining the genetic variation of this introduced population. We extracted DNA from muscle tissue samples (N = 21) and sequenced a region of the ND4 gene to allow for comparison with previously described native Ctenosaura populations. We documented a single haplotype from KI, which means this iguana population likely descended from a single introduction event and one geographic source population (Honduras). If this single haplotype represents an overall reduction in genetic diversity, then this population demonstrates that genetic variability is not always necessary for a species to become established in a new ecological range. This interpretation may have strong implications for invasive species management.