Website review: Pharyngula: Evolution of a polyphen...
mattbert discovered this in Evolution
•2 reviews since Feb 9, 2006
evolution
•scienceblogs.com/pharyngula/2006/02/evolution...
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mattbert discovered 31 months ago- "Scientists have directly observed the evolution of a complex, polygenic, polyphenic trait by genetic assimilation and accommodation in the laboratory. This is important, because it is simultaneously yet another demonstration of the fact of evolution, and an exploration of mechanisms of evolution."
- Dreadnought rated 17 months ago
- PZ Meyers writes about the evolutionary phenomenons of genetic assimilation and accommodation at both his blog Pharyngula and SEED Magazine. Meyers describes a particularly elegant set of experiments that demonstrate how selection can act upon invisible variation within a population to evolve flexible developmental adaptations for a species. A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. A polyphenism is a biological mechanism that causes a trait to be polyphenic. Naysayers of evolution would argue that a polyphenism would be impossible to evolve because it requires "sophisticated genetic control elements that sense elements of the environment and selectively activate different sets of genes depending on the conditions." Putting it that way does makes it sound unlikely and tricky to evolve. However, as Meyers points out, "all phenotypes are conditionally sensitive and dependent on interactions between genes and between genes and the environment--the control elements aren't novel introductions, they're already there! The evolution of polyphenic traits may be more a matter of shifting conditional responses quantitatively in particular directions." The work described by Meyers here empirically shows how a polyphenism evolved in the large caterpillar of the moth Manduca sexta . This species lacks the polyphenism in nature while a closely related species already had it.
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