Climate, competition, and the coexistence of island lizards

Summary1 The influence of environmental temperatures and competition combine to determine the distributions of island lizards. Neither a bioenergetic model nor simple models of competition alone can account for the distributions. A mechanistic, bioenergetic model successfully predicts how the abundance of a solitary Anolis lizard species will decline along an island's elevation gradient. However, the abundance trends for sympatric lizards diverge from the predictions of the non‐interactive model. 2 Here we incorporate competition in the bioenergetic model and examine how different forms of competition modify the temperature‐based abundance predictions. 3 Applying the bioenergetic model with competition to an island chain tests whether the model can successfully predict on which islands two lizards species will coexist. 4 Coexistence is restricted to the two largest islands, which the model predicts have substantially greater carrying capacities than the smaller islands. The model successfully predicts that competition prevents species coexistence on the smallest islands. However, the model predicts that the mid‐sized islands are capable of supporting substantial populations of both species. Additional island characteristics, such as habitat diversity, resource availability and temporal disturbance patterns, may prevent coexistence.