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Schematic representation of evolutionary change determined by adaptation (a), history (b), and chance (c). The effects of chance are demonstrated for a set of clones of a single ancestral genotype, whereas adaptation and history are illustrated for several independent ancestors. Isoclines (dotted line) represent the score location if no changes take place. Adapted from Travisano et al. (1995) and Waagenar and Adami (2004).
