epistasis
Kouyos RD, Silander OK & Bonhoeffer S 2007 Epistasis between deleterious mutations and the evolution of recombination. TREE 22:308-315.
- glossary
- physiological epistasis: the distribution of epistatic interactions among randomly introduced mutations independent of their frequency of occurrence in natural populations
- population epistasis: the distribution of epistatic interactions that occur in a natural population weighted by their occurrence
- no epistasis corresponds to multiplicativity of fitness effects and thus a linear relation between log fitness and number of mutations
- negative or positive epistasis between deleterious mutations implies that mutations interact synergistically or antagonistically in reducing fitness
- we review the experimental data, which, in our view, provide no support for the MDH (mutational deterministic hypothesis), because there is currently no convincing evidence for a predominance of negative epistasis across many taxa
- recently, Sanjuan and Elena (2006) collected data from several previously published experiments and proposed that the dominant form of epistasis correlated with genome complexity
- their conclusions should be taken with some caveats
- most studies that have reached statistical significance find that positive epistasis predominates
- for methodological reasons, these studies mainly come from viruses
- most measurements in higher organisms have not shown significant deviations from zero epistasis
- an apparent decrease in epistasis with increasing genomic complexity might be due to methodological reasons
- the most recent and largest scale eukaryotic study did find significant evidence for positive epistasis
- it is early days to decide whether Sanjuan and Elena's hypothesis is borne out by the data
- their extrapolation for epistasis in higher organisms is based only on five data sets, and did not include a more recent study on yeast (Jasnos & Korona 2007)
