Hc. Proctor et al., MATING-BEHAVIOR AND SPERMATOPHORE MORPHOLOGY - A COMPARATIVE TEST OF THE FEMALE-CHOICE HYPOTHESIS, Canadian journal of zoology, 73(11), 1995, pp. 2010-2020
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.