Competitive PCR reveals the complexity of postcopulatory sexual selection inTeleogryllus commodus

Abstract

The outcome of mate choice depends on complex interactions between males and females both before and after copulation. Although the competition between males for access to mates and premating choice by females are relatively well understood, the nature of interactions between cryptic female choice and male sperm competition within the female reproductive tract is less clear. Understanding the complexity of postcopulatory sexual selection requires an understanding of how anatomy, physiology and behaviour mediate sperm transfer and storage within multiply mated females. Here we use a newly developed molecular technique to directly quantify mixed sperm stores in multiple mating females of the black field cricket, Teleogryllus commodus. In this species, female postcopulatory choice is easily observed and manipulated as females delay the removal of the spermatophore in favour of preferred males. Using twice-mated females, we find that the proportion of sperm in the spermatheca attributed to the second male to mate with a female (S2) increases linearly with the time of spermatophore attachment. Moreover, we show that the insemination success of a male increases with its attractiveness and decreases with the size of the female. The effect of male attractiveness in this context suggests a previously unknown episode of mate choice in this species that reinforces the sexual selection imposed by premating choice and conflicts with the outcome of postmating male harassment. Our results provide some of the clearest evidence yet for how sperm transfer and displacement in multiply mated females can lead directly to cryptic female choice, and that three distinct periods of sexual selection operate in black field crickets.

An Analytical Framework for Estimating Fertilization Bias and the Fertilization Set from Multiple Sperm-Storage Organs

“…Indeed, the closer we get to fertilization, the less we understand about the mechanisms of cryptic female choice. Thus, we know more about female-mediated processes influencing intromission (e.g., Brennan et al 2007), sperm transfer (e.g., Sakaluk and Eggert 1996;Pilastro et al 2004;Bussière et al 2006;Hall et al 2010), and retention of sperm (e.g., Bishop et al 1996;Pizzari and Birkhead 2000;Dean et al 2011;Lüpold et al 2012) than we do about sperm storage and use for fertilization (e.g., Ward 1993;Otronen et al 1997;Có rdoba-Aguilar 1999;Fedina and Lewis 2004;Pattarini et al 2006).…”

Cryptic Female Choice in Crickets and Relatives (Orthoptera: Ensifera)

“…Using "competitive PCR" (based on amplifying microsatellite markers) to quantify the relative contribution of sperm from two different males to the spermatheca in non-virgin females, however, Hall et al (2010) found that the proportion of sperm in storage for the second male to mate increased linearly with the duration of spermatophore attachment for that male in T. commodus. There is strong evidence that in G. bimaculatus ( Fig.…”

“…11.2). Hall et al (2010) similarly quantified the relative amount of sperm in the spermatheca contributed by two males differing in the level of "attractiveness" (latency to copulation in precopulatory trials) in T. commodus. For a given duration of spermatophore attachment, Hall et al (2010) found that "attractive" males contributed more sperm to the spermatheca than "unattractive" males.…”

“…Hall et al (2010) similarly quantified the relative amount of sperm in the spermatheca contributed by two males differing in the level of "attractiveness" (latency to copulation in precopulatory trials) in T. commodus. For a given duration of spermatophore attachment, Hall et al (2010) found that "attractive" males contributed more sperm to the spermatheca than "unattractive" males. This result appears to contrast with Bussière et al (2006), who found that there was no difference between attractive and unattractive males in the rate of sperm transfer to the spermatheca in the same species (Fig.…”

Determinants of reproductive success across sequential episodes of sexual selection in a firefly

“…In T. dalmanni, Corley et al [74] suggest that differences in male fertility, patterns of sperm usage and ejaculate expenditure as a function of female reproductive value could explain extreme variations in paternity share. A recent study on Teleogryllus commodus field crickets [76] suggests a role for both sperm competition and cryptic female choice in determining reproductive success, highlighting the complexity of these post-copulatory interactions.…”