wrights shifting balance theory and the diversification of aposematic signals赖特的转移平衡理论和多元化的警戒色的信号.pdf

Wright’s Shifting Balance Theory and the Diversification of Aposematic Signals Mathieu Chouteau*, Bernard Angers Group for Interuniversity Research in Limnology and Aquatic Environment (GRIL) and Department of Biological Sciences, University of Montreal, Montreal, Canada Abstract Despite accumulating evidence for selection within natural systems, the importance of random genetic drift opposing Wright’s and Fisher’s views of evolution continue to be a subject of controversy. The geographical diversification of aposematic signals appears to be a suitable system to assess the factors involved in the process of adaptation since both theories were independently proposed to explain this phenomenon. In the present study, the effects of drift and selection were assessed from population genetics and predation experiments on poison-dart frogs, Ranitomaya imitator, of Northern Peru. We specifically focus on the transient zone between two distinct aposematic signals. In contrast to regions where high predation maintains a monomorphic aposematic signal, the transient zones are characterized by lowered selection and a high phenotypic diversity. As a result, the diversification of phenotypes may occur via genetic drift without a significant loss of fitness. These new phenotypes may then colonize alternative habitats if successfully recognized and avoided by predators. This study highlights the interplay between drift and selection as determinant processes in the adaptive diversification of aposematic signals. Results are consistent with the expectations of the Wright’s shifting balance theory and represent, to our knowledge, the first empirical demonstration of this highly contested theory in a natural system. Citation: Chouteau M, Angers B (2012) Wright’s Shifting Balance Theory an