Mate choice for offspring performance: major bene®ts or minor costs?

There is considerable disagreement over whether or not gaining viability bene¢ts to o¡spring could be substantial enough to overcome the costs of female choosiness. A recent review suggested that the `lek paradox' might be resolved by large indirect bene¢ts as indicated by highly heritable ornamental traits. We selected males of a wolf spider Hygrolycosa rubrofasciata in relation to their sexual signalling rate (audible drumming). The estimated correlated response in o¡spring viability was rather small (0.12 s.d.). However, it may be large enough if the costs of being choosy are small. In fact, females mate with betterthan-average males just by responding passively to a random drumming signal, and the active choice by females seemed to increase this bene¢t only slightly. In many mating systems, females obtain better-thanaverage males as a consequence of intense male^male competition or because of the extraordinary variance in male signalling. The costs of any additional choice may be so minor that female choice for honestly signalling males may evolve even with minute bene¢ts in o¡spring viability. This may be the general solution to the lek paradox, as most studies report no apparent ¢tness bene¢ts. Publication bias favouring statistically signi¢cant results may have led to an overemphasis on the few studies with large e¡ects.