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Waddington’s canalization revisited

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Mark L. Siegal and Aviv Bergman Waddington’s canalization revisited: Developmental stability and evolution. PNAS 99(16):10528-10532 PNAS page pdf

Siegal and Bergman build on the earlier work of A.Wagner (reviewed below), who showed that canalisation in (models of) gene networksĀ  may evolve as a by-product of stabilising selection. Recall that in Wagner’s model, a regulatory gene network was represented as a matrix and the phenotype as the stable state of the deterministic, discrete-time dynamical process it encodes.

This setup is retained in the present paper but, crucially, situations where the network does not have (or rather: appears not to have) a stable state are considered as well. This allows the authors to decouple the effect of stabilising selection from that of selection for the existence of the steady state of the network. The result is that, perhaps surprisingly, canalisation can be accounted for by the latter mechanism alone, and therefore is an intrinsic property of stable complex networks regardless of whether their evolution is driven by natural selection.

Siegal’s and Bergman’s model has a number of parameters, most notably the interconnectedness of the network (defined as the number of non-zero entries in the matrix). It turns out that highly connected networks display low initial canalisation, but evolve it rapidly and to a greater extent than relatively sparse ones.

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Written by evopapers

July 29, 2010 at 12:00

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