standing variation
James JE, Piganeau G & Eyre-Walker A 2016 The rate of adaptive evolution in animal mitochondria. Mol Ecol 25:67-78.
- the level of adaptive evolution in mitochondria is correlated to the effective population size, as measured by the level of synonymous genetic diversity
- this is expected if the rate of adaptation is limited by the supply of mutations because species with a high Ne are more likely to generate the advantageous mutations that allow them to adapt
- we expect a correlation between ωa and Ne but not necessarily between ωa and πs
- πs is expected to be equal to Neu
- ωa is expected to be independent of the mutation rate
- the observed correlation between ωa and πs is not expected under a model in which all adaptation comes from standing genetic variation
- under this model species with high and low diversity must adapt at the same rate
- if not, then the less diverse species must be waiting for advantageous mutations to occur and hence be limited in their adaptation by the supply of mutations
- the correlation between the rate of adaptive evolution and the level of neutral diversity is consistent with the results of Gossmann et al. (2012) who observed a correlation between the rate of adaptive evolution and the effective population size in the nuclear genes of 13 independent pairs of animal, fungal and plant species
- our major result, that mitochondria undergo substantial levels of adaptive evolution, appears to be inconsistent with previous work indicating that nuclear genes in regions of low recombination undergo little or no adaptive evolution, at least in Drosophila
