Bite or flight? Behavioral interactions between bark anoles and brown anoles in their nonnative range

Both intra- and interspecific interactions play crucial roles in defining the structure of ecological communities. However, the specific behavioral processes underlying this structuring are often unclear and must be inferred from contemporary interactions. Rapid spread of nonnative species has resulted in increasingly homogenized communities, and this homogenization provides an excellent opportunity to study the behavioral processes that lead to stable communities of introduced species in novel habitats. Here, we compared the behavior of brown anoles (Anolis sagrei) and bark anoles (A. distichus) when faced with an incursion by an unknown brown anole to examine the intra- and interspecific interactions underlying the structuring of novel communities in South Florida, USA. We found that brown anoles were consistently more aggressive toward intruders than bark anoles, and this pattern was accentuated when they encountered intruders of the same sex. Conversely, bark anoles were likely to flee when they encountered intruder brown anoles. We also found that brown anoles were likely to attack intruders regardless of whether they engaged in aggressive behavioral displays while bark anoles were likely to flee regardless of whether the intruder engaged in behavioral displays. Our findings suggest that behavioral interactions could play a significant role in structuring the novel Anolis communities in South Florida and demonstrate the importance of aggressive interactions both within and between species.