Male and female mate choice in harvestmen: General patterns and inferences on the underlying processes

Abstract

Harvestmen belong to the order Opiliones, and, unlike other arachnids, they are highly polygynandrous, with both males and females mating multiply throughout the breeding season. In this chapter, we review the current information on sexual selection in the group, focusing mostly on intersexual interactions. Particularly, we provide an overview of harvestman mating systems, examine different temporal phases of male-female sexual interactions, and explore cases of sex role reversal. Several traits in harvestmen make them unique in the context of most previous studies of sexual selection. First, they have evolved an intromittent organ independently of other well-studied taxa, such as insects, spiders, and mammals. Second, the lack of long-range perception mechanisms reduces the window of opportunity for males and females to exchange information during the very short period between the first contact and intromission. In some cases, however, acceptance or rejection of a mate may be based on information gathered before contact, such as the quality of the male territory or the presence of eggs in his nest. Regardless of the role of pre-copulatory interactions, actual fertilization success is likely to be strongly dependent on the outcome of copulatory and post-copulatory processes. In this sense, the fact that most species are highly promiscuous and have sperm cells that lack flagella, which are stored near to the tip of the ovipositor and used to fertilize eggs immediately before oviposition, renders Opiliones a fertile ground to study the role of cryptic female choice, sperm competition, and sexual conflict.