MATING-BEHAVIOR AND SPERMATOPHORE MORPHOLOGY - A COMPARATIVE TEST OF THE FEMALE-CHOICE HYPOTHESIS

Complex, species-specific morphology of genitalia or ''paragenitalia'' such as spermatophores is traditionally considered an adaptation to p revent heterospecific matings. Eberhard argued against this lock-and-k ey hypothesis and suggested that elaborate male genitalia evolve throu gh female preference for increased tactile stimulation. He found suppo rt for this argument in a cross-taxon comparison of spermatophore comp lexity among species with different degrees of contact between the sex es during spermatophore transfer. After expanding Eberhard's list of s pecies, we tested the female-choice hypothesis with appropriate contro ls for phylogeny and using naive human subjects to rank spermatophore complexity. Our results uphold Eberhard's conclusion that the lock-and -key hypothesis does not explain the distribution of spermatophore com plexity among taxa; however, they do not clearly support female choice as an alternative explanation. Other factors that may influence sperm atophore complexity include environmental stress and whether spermatop hores are deposited on a substrate. Because we seldom know what parts of a spermatophore are touched by females, or whether there are sperma tophore-associated pheromones, human visual assessment may not always allow accurate judgement of realized spermatophore complexity.