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Table 1 Overview of key studies on the relationship between degeneracy, robustness, complexity and evolvability.

From: Degeneracy: a link between evolvability, robustness and complexity in biological systems

  Relationship Summary Context Ref
1) Unknown whether degeneracy is a primary source of robustness in biology Distributed robustness (and not pure redundancy) accounts for a large proportion of robustness in biological systems (Kitami, 2002), (Wagner, 2005). Although many traits are stabilized through degeneracy (Edelman and Gally, 2001) its total contribution is unknown. Large scale gene deletion studies and other biological evidence (e.g. cryptic genetic variation) [43, 61, 2]
2) Degeneracy has a strong positive correlation with system complexity Degeneracy is positively correlated and conceptually similar to complexity. For instance degenerate components are both functionally redundant and functionally independent while complexity describes systems that are functionally integrated and functionally segregated. Simulation models of artificial neural networks are evaluated based on information theoretic measures of redundancy, degeneracy, and complexity [33]
3) Degeneracy is a precondition for evolvability and a more effective source of robustness Accessibility of distinct phenotypes requires robustness through degeneracy Abstract simulation models of evolution [3]
4) Evolvability is a prerequisite for complexity All complex life forms have evolved through a succession of incremental changes and are not irreducibly complex (according to Darwin's theory of natural selection). The capacity to generate heritable phenotypic variation (evolvability) is a precondition for the evolution of increasingly complex forms. Theory of natural selection [62]
5) Complexity increases to improve robustness According to the theory of highly optimized tolerance, complex adaptive systems are optimized for robustness to common observed variations in conditions. Moreover, robustness is improved through the addition of new components/processes that are integrated with the rest of the system and add to the complexity of the organizational form. Based on theoretical arguments that have been applied to biological evolution and engineering design (e.g. aircraft, internet) [29, 35, 30]
6) Evolvability emerges from robustness Genetic robustness reflects the presence of a neutral network. Over the long-term this neutral network provides access to a broad range of distinct phenotypes and helps ensure the long-term evolvability of a system. Simulation models of gene regulatory networks and RNA secondary structure. [6, 4]
  1. The information is mostly taken (with permission) from [3]