Table 2.
Linkage theories.
| name | valid range | recombination | back mutations | mutations of largest effect |
|---|---|---|---|---|
| background selection (BGS) | removal of deleterious mutations always works | ≥0 | irrelevant | −−−− |
| Muller's ratchet (MR; slow regime) | removal of slightly deleterious mutations fails rarely (‘bad luck’) | 0a, ≥0b | usually neglected | −−− |
| Muller's ratchet (MR; fast regime) | removal of slightly deleterious mutations is expected to fail | 0a, ≥0c | 0a, ≥0c | −− |
| nearly neutral theory (NN) | very slightly deleterious and positive mutations accumulate (selection too weak to discern) | ≥0 | yes | +/0/ − |
| clonal interference (CI) | several advantageous clones interfere with each others' selection | 0 | ++/+++ | |
| interference selection (IS) | several advantageous mutations interfere with each other under partial linkage | >0d | ++/+++ | |
| hitch-hiking (HH) | strongly selected mutations drag less strongly selected (potentially deleterious) mutations to fixation. | ≥0 | ++++ |
+= advantageous, 0 = neutral and −= deleterious mutations, where repeated symbols indicate stronger selection.
aClassical theory of Muller's ratchet (Haigh 1978).
b‘Hill-Robertson Interference’ (Kaiser & Charlesworth 2009).
c‘Weak selection Hill–Robertson effect’ (McVean & Charlesworth 2000).
d‘Hill–Robertson effect’ (Roze & Barton 2006).