Evolutionary Developmental Biology: Developmental Bias and Constraint


Developmental trajectories can be more readily altered in some ways than others by mutations in the genes that govern them. This is developmental bias. Both positive and negative biases are possible: these can be called, respectively, developmental drive and developmental constraint. These processes may have major effects on the direction of evolutionary change. Here, such effects are considered both in general and through looking at particular examples, including the evolution of centipedes and turtles. It is noted that developmental bias may be especially important in the origins of evolutionary novelties – such as the turtle ‘shell’. Developmental bias relates to the structure of variation in developmental pathways. When such variation is highly structured (high degree of bias) there are limits to the ‘evolvability’ of the creatures concerned. In contrast, cases of low bias mean that evolvability is correspondingly higher.

Key Concepts:

  • Developmental bias refers to situations in which some variant developmental trajectories are more probable than others.

  • It is likely that such bias is ubiquitous in nature but that its extent is highly variable.

  • Developmental bias may interact with natural selection to determine the direction of evolutionary change and/or the array of character states found.

  • Bias is best studied by the investigation of particular examples.

  • The evolution of centipede segment number and the origin of the turtle shell are used as examples herein.

  • Developmental bias is complementary to the concept of evolvability.

  • Although most discussion of bias, evolvability and related concepts has taken place in the era of evolutionary developmental biology (1980 to the present), earlier discussions of similar ideas (but using different terms) can be traced back to Charles Darwin and Alfred Russel Wallace.

Keywords: developmental bias; microevolution; macroevolution; developmental constraint; organismic form; segmentation; novelty; evolvability

Figure 1.

The current view of the pattern of phylogenetic relationship of the six centipede orders, including the four listed in Table plus the extinct Devonobiomorpha (number of leg‐pairs unknown) and the rare Australasian Craterostigmomorpha (only two species; 15 leg‐pairs). This pattern is based on several studies conducted over the last three decades.



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Further Reading

Arthur W (2011) Evolution: A Developmental Approach. Oxford: Wiley‐Blackwell (chapter 13 is especially relevant).

Gould SJ (1983) Hen's Teeth and Horse's Toes: Further Reflections in Natural History. New York: Norton.

Gould SJ and Lewontin RC (1979) The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London B 205: 581–598.

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Schwenk K (1995) A utilitarian approach to evolutionary constraint. Zoology 98: 251–262.

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Arthur, Wallace(Nov 2011) Evolutionary Developmental Biology: Developmental Bias and Constraint. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001066.pub3]