Spatial mosaic formation through frequency-dependent selection in Mullerian mimicry complexes

Authored by TN Sherratt

Date Published: 2006

DOI: 10.1016/j.jtbi.2005.09.017

Sponsors: National Science and Engineering Research Council of Canada (NSERC) Canada Foundation for Innovation (CFI) Ontario Innovation Trust

Platforms: No platforms listed

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

Although contemporary models of Mullerian mimicry have considered the movement of interfacial boundaries between two distinct mimetic forms. and even the possibility of polymorphisms in two patch systems, no model has considered how multiple forms of Mullerian mimics might evolve and be maintained over large geographical areas. A spatially explicit individual-based model for the evolution of Mullerian mimicry is presented, in which two unpalatable species are distributed over discrete cells within a regular lattice. Populations in each cell are capable of genetic drift and experience localized dispersal as well as frequency-dependent selection by predators. When each unpalatable prey species was introduced into a random cell and allowed to spread, then mimicry evolved throughout the system in the form of a spatial mosaic of phenotypes, separated by narrow ``hybrid zones{''}. The primary mechanism generating phenotypic diversity was the occasional establishment of new mutant forms in unoccupied cells and their subsequent maintenance (and spread) through frequency-dependent selection. The mean number of discrete clusters of the same morph that formed in the lattice was higher the higher the intensity of predation, and higher the lower the dispersal rate of unpalatable prey. Under certain conditions the hybrid zones moved, in a direction dependent on the curvature of their interfacial boundaries. However, the mimetic mosaics were highly stable when the intensity of predation was high and the rate of prey dispersal was low. Overall, this model highlights how a stable mosaic of different mimetic forms can evolve from a range of starting conditions through a combination of chance effects and localized frequency-dependent selection. (c) 2005 Elsevier Ltd. All rights reserved.

Tags

Evolution movement Natural-selection Radiation Hypothesis Heliconius butterflies Warning-color Hybrid zones Shifting balance Phylogenetic evidence