ABSTRACT
312In most sexually reproducing species, males and females follow different strategies to maximize their reproductive success. Sex-specific strategies evolved because males can increase their reproductive success by mating frequently and promiscuously, whereas females benefit from being selective. Simultaneously hermaphroditic animals produce both eggs and sperm at the same time but the reproductive investment in the two sexual functions might be asymmetric. This may lead to a conflict of interests in hermaphrodites because the male and female functions retain their separate interests even though they are united in the same individual. Consequently, in simultaneous hermaphrodites selection on male reproductive traits also influences female traits and vice-versa. This chapter reviews reproductive strategies in stylommatophoran gastropods, a highly diverse group of molluscs exceeding 30,000 species, all of them being hermaphrodites. Stylommatophoran species show diverse and very complex reproductive organs, bizarre mating behaviors and variable breeding systems including cross-fertilization, self-fertilization, and a mixture of both. Stylommatophoran gastropods also developed a variety of morphological structures and behaviors such as egg cannibalism, egg retention and ovoviviparity to increase offspring survival in quite different environments. In stylommatophoran gastropods, almost all reproductive characters appear to be shaped by both natural and sexual selection, and there is increasing evidence that intersexual counter-adaptations may drive correlated reproductive character evolution in this group. Behaviors and traits to enhance survival of both eggs and hatchlings—the other important component of reproductive strategies—are shaped by natural selection.
