Sexual selection within the female genitalia in lepidoptera

Abstract

The genitalia of male and female Lepidoptera are complex organs, composed of several structures that exhibit great diversity of shapes, sizes, and positions, suggesting that they have evolved in a relatively rapid and divergent way. In this chapter, we explore the selective pressures responsible for the evolution of genital morphology in the Lepidoptera, emphasizing the possible role of post-copulatory intersexual selection (PCIS) mechanisms (cryptic female choice and sexual conflict). Our exploration is in great extent speculative because knowledge on the functional morphology of genitalia in this group is limited. We start by describing the complexity and diversity of genitalia in Lepidoptera, discussing the available information about the role of the different structures in copulation. Then, we discuss possible ways in which PCIS and other types of selective pressures could have influenced the evolution of genitalia by developing illustrative hypothesis for several structures whose function is not well understood. Finally, we describe in detail recent experimental and comparative studies aimed at understanding the function and selective pressures responsible for the evolution of a female genital trait known as signum.