Fig. 1.

The relation between genic capture mechanism (Rowe and Houle 1996) and trade-offs hypothesis of the maintenance of genetic variance in sexual traits. Costs associated with expression of sexually selected traits (SST) have two consequences: condition-dependence of SST, and trade-offs between naturally selected traits (NST) and SST. In genic capture, SST take over genetic variance in condition, which is created independently (e.g. by influx of deleterious mutations or host-parasite arms race). We argue (lower path) that trade-offs associated with sexual traits increase the scope for the maintenance of genetic variation in sexual traits themselves, but also in other, naturally selected, traits (NST) involved in those trade-offs (see text). The observed V_A in sexual traits might be a combination of both mechanisms, but note that trade-offs can also contribute to V_A in traits affecting condition