TABLE 2.
Glossary of repeatedly used notation
| Symbol | Usage (relevant equation in the text) |
|---|---|
| A | Measure of postmating asymmetry, measured as a difference between the more successful minus the less successful direction of hybridization (11) |
| C | Threshold value of the hybrid breakdown score that leads to complete postmating isolation; the value is scaled as a multiple of the average effect of the most deleterious DMI (44) |
| CV | Coefficient of variation of effects of both B and U DMIs (13) and (24) |
| gB | 1 − gU, fraction of substitutions that can contribute to B DMIs (23) |
| gU | Fraction of substitutions relevant to U DMIs that occur at “female-acting” loci (17) |
| h0 | Average contribution of B DMIs to the hybrid breakdown score, assuming that the U DMIs have been scaled to have an average effect of 1 (21) |
 |
No. of bidirectional (B) DMIs accumulated after divergence time t (1) |
 |
No. of unidirectional (U) DMIs experienced in a cross with a taxon 1 maternal parent |
| p | Probability that an allelic difference at two B loci produces a B DMI (22) |
| pU | Probability that allelic differences at one “male-acting” locus and one “female-acting” locus produce a U DMI (5) |
 |
Contribution to the hybrid breakdown scores (both  and  ) from B DMIs (1) and (3) |
| Sij | Hybrid breakdown score produced with a taxon i maternal parent (1) |
 |
Contribution to the hybrid breakdown score  from U DMIs |
| TC | Geometric mean of  and  (9) |
 |
Divergence time at which E(Sij) = C, (9), i.e., the time at which the expected breakdown score corresponds to complete postmating isolation |
| v(S) | Function describing how fitness declines as the hybrid breakdown score, S, increases (10) |
| α | Exponent in the function describing how fitness declines as DMIs accumulate (10) |
| β | p(1 − gU)/(pUgU), ratio of the expected no. of B DMIs to the expected no. of U DMIs (26) |
| δ1 | υ1 −  , difference in the relative taxon-specific rates of evolution of female-acting vs. male-acting loci that contribute to U DMIs (4b) |
| η | h0β, ratio of the expected contribution to the hybrid breakdown scores caused by B DMIs (which have average effect h0) to the expected contribution from U DMIs (which are assumed to have average effect 1) (28) |
| τ | t/TC, scaled divergence time between the taxa hybridized (19) and (25) |