evolvability
Milton CC, Ulane CM & Rutherford S 2006 Control of canalization and evolvability by Hsp90. PLoS ONE 1:e75.
- the extent to which the Hsp90 chaperone also controls smaller and more likely adaptive changes in natural quantitative traits has been unclear
- Hsp90 buffering was remarkably specific to certain normally invariant and highly discrete quantitative traits
- like the qualitative trait phenotypes controlled by Hsp90, highly discrete quantitative traits such as scutellor and thoracic bristle number are threshold traits
- the sensitivity of these traits to many types of variation was coordinately controlled
- while continuously variable bristle types and wing size, and critically invariant left-right wing asymmetry, remained relatively unaffected
- in replicate populations in which Hsp90 was specifically impaired, heritability and 'extrinsic evolvability', the expected response to selection, were also markedly increased
- for any particular individual or genotype in which Hsp90 was impaired, the size and direction of its effects were unpredictable
- the trait and genetic-background dependence of Hsp90 effects and its remarkable bias toward invariant or canalized traits support the idea that traits evolve independent and trait-specific mechanisms of canalization and evolvability through their evolution of non-linearity and thresholds
