Is modularity necessary for evolvability? Remarks on the relationship between pleiotropy and evolvability

Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
Biosystems (Impact Factor: 1.55). 06/2003; 69(2-3):83-94.
Source: PubMed


Evolvability is the ability to respond to a selective challenge. This requires the capacity to produce the right kind of variation for selection to act upon. To understand evolvability we therefore need to understand the variational properties of biological organisms. Modularity is a variational property, which has been linked to evolvability. If different characters are able to vary independently, selection will be able to optimize each character separately without interference. But although modularity seems like a good design principle for an evolvable organism, it does not therefore follow that it is the only design that can achieve evolvability. In this essay I analyze the effects of modularity and, more generally, pleiotropy on evolvability. Although, pleiotropy causes interference between the adaptation of different characters, it also increases the variational potential of those characters. The most evolvable genetic architectures may often be those with an intermediate level of integration among characters, and in particular those where pleiotropic effects are variable and able to compensate for each other's constraints.

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    • "A property of living systems that is well suited to explain the origin of morphological disparity is their modular organization (Wagner 1996; Hansen 2003; Wagner et al. 2007; Pavlicev and Hansen 2011). Organisms are hypothesized to be constructed from distinct sub-units termed modules that are highly integrated internally and behave quasi-independently during ontogeny and evolution (Wagner 1996; von Dassow and Munro 1999; Hansen et al. 2003; Klingenberg et al. 2003; Wagner et al. 2007; Kuratani 2009). Modularity is tightly linked to the concept of morphological integration, which postulates that functionally or developmentally related traits should form highly cohesive morphological units (Olson and Miller 1958; Cheverud 1982; Zelditch 1987; Cheverud 1996; Chernoff and Magwene 1999). "
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