Population Viability of Nonnative Mediterranean House Geckos (Hemidactylus turcicus) at an Urban Site Near the Northern Invasion Front

Biological invasions are one of the most serious threats to biodiversity conservation. Although success and impacts of many invaders, particularly ectotherms, are likely to be limited by a combination of climatic and demographic factors, human modifications to the environment can facilitate distributional expansion into otherwise low-quality landscapes. We assessed factors that might promote or preclude population viability of a nonnative ectotherm, Hemidactylus turcicus (Mediterranean House Gecko), within an urban center at the northern periphery of its known North American range. Mediterranean House Geckos are increasingly apparent in the southeastern United States, but their potential for establishment and spread in more temperate regions is less well known. We gathered data using capture-recapture methods and the unique dorsal patterns of individual geckos. Despite a more temperate climate compared to other areas in their introduced range, and refuge temperatures falling below the critical thermal minimum previously documented for other introduced Mediterranean House Gecko populations, geckos survived the winter and reproduced successfully. Cormack-Jolly-Seber open population models did not provide definitive evidence regarding changes in population size over the study period. The tendency for this introduced species to establish populations primarily within urban centers may suggest that negative impacts associated with this northerly expansion are minor. Nonetheless, a high potential for range expansion suggests a need to assess a potentially growing suite of ecosystem interactions.