Behaviour 2019
Frequency dependence shapes the adaptive landscape of imperfect Batesian mimicry
Susan D. Finkbeiner1,6, Patricio A. Salazar2, Sofia Nogales3, Cassidi E. Rush4, Adriana D. Briscoe5, Ryan I. Hill4, Marcus R. Kronforst1, Keith R. Willmott2, Sean P. Mullen6. 1University of Chicago, Chicago, IL, United States; 2University of Florida, Gainesville, FL, United States; 3Pontifica Universidad Catolica del Ecuador, Quito, , Ecuador; 4University of the Pacific, Stockton, CA, United States; 5University of California, Irvine, Irvine, CA, United States; 6Boston University, Boston, MA, United States

Despite more than a century of research on the evolution and maintenance of mimetic signals, the relative frequencies of models and mimics necessary to establish and maintain Batesian mimicry in natural populations remain understudied. Here we investigate the frequency-dependent dynamics of imperfect Batesian mimicry, using predation experiments involving artificial butterfly models. We use two geographically distinct populations of Adelpha butterflies that vary in their relative frequencies of a putatively defended model (A. iphiclus) and Batesian mimic (A. serpa). We found that in Costa Rica, where both species share similar abundances, Batesian mimicry breaks down, and predators readily attack artificial butterfly models of the presumed mimic, A. serpa. By contrast, in Ecuador, where A. iphiclus (model) is significantly more abundant than A. serpa (mimic), both species are equally protected from predation. Our results provide compelling evidence that imperfect Batesian mimicry is frequency-dependent on the relative abundance of models and mimics in natural populations, and contribute to the growing body of evidence that complex dynamics influence the evolution of mimetic traits.