| Mating may thus be assortative as females mate selectively with males of the same vocal background, discouraging gene migration. |
| In both cases the result is assortative mating or breeding among mates that possess similar genes. |
| Condition-dependent preferences will emerge in both sexes as a result and presumably will combine to make mating even more strongly assortative. |
| In the second part of the paper we consider assortative mating by parental income. |
| But in any case the existence of assortative mating for such traits is significant. |
| Finally, we found no evidence of assortative preference for size. |
