1. As animals move through their environments they encounter a variety of substrates, which have important effects on their locomotor performance. Habitat modification can alter the types of substrates available for locomotion. In particular, many types of artificial substrates have been added to urban areas, but effects of these novel surfaces on animal locomotion are little-known. 2. In this study, we assessed locomotor performance of two Anolis lizard species (A. cristatellus and A. stratulus) on substrates that varied in inclination and surface roughness. Rough substrates represented the tree trunks and branches typically used in natural forest habitats, whereas smooth, vertical substrates captured the qualities of artificial surfaces, such as posts and walls, available in human-modified habitats. We then observed habitat use to test the habitat constraint hypothesis — that lizards should more frequently occupy portions of the habitat in which they perform better. 3. Increased inclination and decreased surface roughness caused lizards to run slower. Both A. cristatellus and A. stratulus ran slowest on the smooth, vertical surface, and A. cristatellus often slipped and fell on this surface. In contrast to predictions, both species frequently used smooth, vertical substrates in the wild. Anolis cristatellus occupied artificial substrates 73% of the time in human-modified habitats despite performing worse than A. stratulus on the smooth, vertical track. We therefore rejected the habitat constraint hypothesis for anoles in these human-modified habitats. 4. Despite overall poor performance on the smooth, vertical track, A. cristatellus had a significant morphology-performance relationship that supports the prediction that selection should favor smaller lizards with relatively longer limbs in human-modified habitats. The smaller-bodied A. stratulus performed better than A. cristatellus on smooth, vertical substrates and therefore may not be exposed to the same selective pressures. 5. We contend that habitat modification by humans may alter morphology-performance-habitat use relationships found in natural habitats. This may lead to changes in selective pressures for some species, which may influence their ability to occupy human-modified habitats such as cities.

Kolbe et al_Function_Ecology_data_dryadThe Excel file has three worksheets, one each for data on locomotor performance, morphology, and habitat use of two species of Anolis lizards from the British Virgin Islands.Kolbe_Function_Ecology_data_dryad.xlsx