Do differences in bite force and head morphology between a native and an introduced species of anole influence the outcome of species interactions?

Species invasions may drive native species to extinction. Yet, the role of competition with a closely related native species in the establishment success of an invasive species remains poorly understood. Indeed, opportunities to study native-invasive competition in action are rare, especially at the very first stages of the invasion. We studied the recent invasion of the lizard Anolis cristatellus in Dominica, where the native Anolis oculatus occurs. We examined the species difference in bite force as a proxy for fighting ability and access to food resources, and its effect on the establishment success of the invasive species. We measured head morphology and bite force of 371 and 129 adults of both species, and compared four allopatric and five sympatric populations in banana farms in an area (Calibishie) where the two species have been in contact for only a few years. This study revealed higher absolute bite forces of A. oculatus, ruling out the superior fighting ability hypothesis as a determinant for the establishment of A. cristatellus in Calibishie. The species differences in bite force and head morphology are present in allopatry and sympatry, suggesting that recent interspecific competition has no observable effect on these traits. We discuss other possible mechanisms allowing the establishment success of A. cristatellus in Dominica.