Ecological character displacement between a native and an introduced species: the invasion of Anolis cristatellus in Dominica.
Species invasions are a global scourge. Nonetheless, they provide the appropriate evolutionary setting to rigorously test the role that interspecific competition plays in species evolution. The process of ecological character displacement, in which species diverge in sympatry to minimize resource use overlap, is one example. Here, we examine whether ecological character displacement occurs as the result of a species invasion and, if so, whether morphological adaptations subsequently evolve. We studied the invasion of the lizard Anolis cristatellus in Dominica, where the native Anolis oculatus occurs, and compared nine allopatric and 11 sympatric populations at two scales: across the island, where A. cristatellus invaded since 1998, and in the northeastern region (Calibishie), where the species arrived in 2014. Perch height and diameter, as well as body, limb and toepad traits, were measured on 593 adults. In sympatry, habitat divergence occurred rapidly but was associated with morphological divergence at the island scale only: A. oculatus perched higher and possessed shorter limbs, while A. cristatellus moved downward with associated longer limbs and, in females, fewer toepad lamellae. The different results for the two scales suggest that sympatry is too recent at Calibishie for morphological trait evolution to occur.