My dissertation research has focused on the ecological niche of the brown anole lizard, Anolis sagrei, as it relates to invasion success. I tested whether human affiliation in A. sagrei could be explained by lack of physiological tolerance for forested habitats in part of its introduced range by experimentally maintaining lizards in enclosures in forested and suburban habitats (Chapter 1). I found that lizards could tolerate forest conditions, and therefore currently unoccupied forested habitats in the introduced range may eventually be colonized. In a comparative study (Chapter 2), I measured resource use and resource availability among several native and introduced populations in vegetated and disturbed habitats. Although A. sagrei is a generalist at the species level, I found that populations varied in degree of niche breadth across the native and introduced range. Anolis sagrei had a broader niche in the introduced range when some resources, prey taxa and microclimate, were considered, but was specialized on a third axis, structural habitat. Preference for and specialization upon disturbed habitat structural resources may be more important for invasion success than prey or microclimate resources. To test whether a native population in a vegetated habitat also preferred and specialized upon disturbed habitat resources, I experimentally compared lizard perch use in the presence and absence of artificial perches (Chapter 3). Treatment females became more generalized than controls relative to perch availability, while treatment males became more specialized, with the sex differences due to social structure and sexual dimorphism. Anolis sagrei is a successful invader in part because it has a wide range of ecological tolerance at the species level (Chapter 2), but also because populations retain the ability to use preferred resources and rapidly incorporate them when they become available (Chapters 1, 3). Human-modified habitats provide some of these preferred resources in the form of low, broad perches in open areas (Chapters 2, 3). Thus not only are they ecologically broad and behaviorally flexible, but brown anoles are also in a sense pre-adapted to urban conditions, making them excellent colonists of disturbed areas in both their native range and new geographic areas.