Genetic variation optimal

Evolution of chemical defenses according to the optimal defense theory presumes, in addition to costly defenses, that there is genetic variation for the defensive metabolites, that herbivory is the major selective agent for such metabolites, and that the chemical trait in question is efficient in reducing herbivory (Stamp 2003). Research on macroalgal chemical defenses has strongly emphasized the last precondition, which has mainly been studied by testing the deterrence effects of secondary metabolites in bioassays. The defensive role for the trait has been assumed on the basis of deterrence it provides. Veiy little research on the first two... 

Horvitz 1989, Hairston Dillon 1990) are important sources of genetic variation. This sort of variation would be expected to increase genetic correlations, in contrast to the optimal-world case. Some believe that laboratory studies of field-evolved populations are therefore biased toward rejecting the optimal-world scenario and are not relevant to the question (Service Rose 1985). 

If the optimal phenotype varies regionally, genetic variation will tend to be maintained. The controversial idea that differences between human races and ethnic groups in intelligence may be partly genetic depends on the validity of the scenario that there has been geographic variation in optimal intelligence level (e.g. Rushton 1995). 

McLeod HL, Papageorgio C, Watters JW. Using genetic variations to optimize cancer chemotherapy. Clinical Advances in Haematology and Oncology 2003 1 107-11. 

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