Cryptic female choice

Abstract. The Eucalyptus weevil, Gonipterus scutellatus, shows a complex copulation behaviour whose duration is extremely variable, from less than one hour to more than two days. We tested different hypotheses that could explain the adaptive significance of prolonged copulations. Male genitalia is unable to reach to the interior of the espermatheca of the female, where the sperm of previous matings are stored, so prolonged copulation does not function to remove rivals' sperm.

Mating plugs have been proposed as a mechanism that has evolved to avoid sperm competition. Their structure and composition vary across taxa and are related to the effectiveness of its function. This effectiveness could be related to different evolutionary interests of the sexes. Urophonius brachycentrus and Urophonius achalensis (Scorpiones, Bothriuridae) are highly suitable species to study mating plugs because both are monandrous species with specific morphological and physiological responses in the female's genitalia. Here, we analyze (a) the morphology and fine structure of the mating plugs of both species, (b) the site of production in males and the formation process of the mating plug, and (c) the changes that it undergoes over time in the female's reproductive tract. In both species, a complex mating plug obliterates the female's genital aperture and fills the genital atrium. We observed considerable interspecific variation in the mating plug morphology. A mating hemi-plug was found surrounding the capsular lobes of the hemispermatophore, which could have a mixed composition (involving portions of the hemispermatophore and glandular products). The glandular portion was transferred in a semi-solid state filling the female's genital atrium and then hardening. Changes that the plug undergoes in the female's genitalia (darkening and increase of the "distal" area of the plug) indicate a participation of the female to the formation of this type of plug. Our study provides new insights into the plugging phenomenon in scorpions, and we discussed the adaptive significance as a post-copulatory mechanism to avoid sperm competition. K E Y W O R D S

Direct costs and benefits to females of multiple mating have been shown to have large effects on female fecundity and longevity in several species. However, with the exception of studies examining genetic benefits of polyandry, little attention has been paid ...

Female mammals may exert choice for mates directly by mating selectively. Alternatively, females can mate promiscuously, allowing sperm competition and/or cryptic female choice to operate. Primate sexual behaviour is probably a compromise between conflicting male and female interests, so it may be important to examine female mating behaviour independently from male influence to better understand female mating strategies. To explore how female behaviour and ovarian cycle phase influence the choice and number of mates in female longtailed macaques, we conducted a pair-choice test where females had complete control over access to males. Subjects were six females and four males. Females were presented with a different pair of males twice a day. Each male was in an adjacent chamber. Females could enter freely and were allowed two entries per male pair. Entry and subsequent copulation with a male was defined as a choice with mating. Females saw each male every day; the males within a pair alternated in a fixed order. We related the females' mating pattern to the females' mating pattern to menstrual cycle stage and timing of ovulation, as determined from faecal progestogen profiles. Females chose and mated with males promiscuously in all periods of their menstrual cycle (prefertile, fertile and postfertile). Overall, females apportioned choices with mating and number of copulations evenly across males. In general, female preferences were not based on male dominance rank. Further investigation is needed to better understand the nature of mating preferences and the adaptive significance of promiscuity in female primates.

Morphological variation of the spermatheca in the garden snail Cantareus aspersus. Spermathecal morphology is known to play an important role in postcopulatory sexual selection of many invertebrates. In helicid land snails, the spermatheca is subdivided into tubules, whose number is sometimes subject to a strong inter-individual variation. Significance of this variation for postcopulatory sexual selection is unknown, but it might

Marine and freshwater environments support numerous species of teleost fish with a wide and diverse range of reproductive strategies. Despite the considerable interest in fish reproduction, our knowledge regarding ejaculate traits and factors affecting them is limited. Using computer-assisted sperm analysis (CASA) I measured ejaculate traits (sperm swimming speed, motility, path trajectory, longevity and concentration) from sexually mature chinook salmon (Oncorhynchus tshawytscha) activated in freshwater and ovarian fluid. I also looked at these ejaculate traits in relation to measures of male quality (body condition) and investment into reproduction (relative testes mass). Furthermore, I determined the chemical composition of seminal and ovarian fluid and looked at the effect these fluids have on sperm behaviour. A considerable amount of intraspecific variation existed in all ejaculate traits measured, and investment into reproduction (relative testes mass) was dependent on male bo...

ABSTRACT In those animals where females mate with multiple partners, selection might favor males with small advantageous features of genital morphology, biochemical makeup of accessory sexual glandular secretions, or patterns of copulatory behavior. Because anatomical and physiological qualities of the female reproductive tract may favor such advantageous masculine features, the term "cryptic female choice" refers to this feminine mechanism of sexual selection at the copulatory and postcopulatory levels. Much evidence pertaining to cryptic female choice derives from research on insects and other groups of invertebrates. The purpose of this brief review is to examine some examples of how cryptic female choice may have influenced genital evolution in primates.

Postmating sexual selection theory predicts that in allopatry reproductive traits diverge rapidly and that the resulting differentiation in these traits may lead to restrictions to gene flow between populations and, eventually, reproductive isolation. In this paper we explore the potential for this premise in a group of damselflies of the family Calopterygidae, in which postmating sexual mechanisms are especially well understood. Particularly, we tested if in allopatric populations the sperm competition mechanisms and genitalic traits ...

It is now clear in many species that male and female genital evolution has been shaped by sexual selection. However, it has historically been difficult to confirm correlations between morphology and fitness, as genital traits are complex and manipulation tends to impair function significantly. In this study, we investigate the functional morphology of the elongate male intromittent organ (or processus) of the seed bug Lygaeus simulans, in two ways. We first use micro-computed tomography (micro-CT) and flash-freezing to reconstruct in high resolution the interaction between the male intromittent organ and the female internal reproductive anatomy during mating. We successfully trace the path of the male processus inside the female reproductive tract. We then confirm that male processus length influences sperm transfer by experimental ablation and show that males with shortened processi have significantly reduced post-copulatory reproductive success. Importantly, male insemination func...

Multiple mating by females is widely thought to encourage post-mating sexual selection and enhance female fitness. We show that whether polyandrous mating has these effects depends on two conditions. Condition 1 is the pattern of sperm utilization by females; specifically, whether, among females, male mating number, m (i.e. the number of times a male mates with one or more females) covaries with male offspring number, o . Polyandrous mating enhances sexual selection only when males who are successful at multiple mating also sire most or all of each of their mates' offspring, i.e. only when Cov ♂ ( m , o ), is positive. Condition 2 is the pattern of female reproductive life-history; specifically, whether female mating number, m , covaries with female offspring number, o . Only semelparity does not erode sexual selection, whereas iteroparity (i.e. when Cov ♀ ( m , o ), is positive) always increases the variance in offspring numbers among females, which always decreases the intensi...

It is now clear in many species that male and female genital evolution has been shaped by sexual selection. However, it has historically been difficult to confirm correlations between morphology and fitness, as genital traits are complex and manipulation tends to impair function significantly. In this study, we investigate the functional morphology of the elongate male intromittent organ (or processus) of the seed bug Lygaeus simulans, in two ways. We first use micro-computed tomography (micro-CT) and flash-freezing to reconstruct in high resolution the interaction between the male intromittent organ and the female internal reproductive anatomy during mating. We successfully trace the path of the male processus inside the female reproductive tract. We then confirm that male processus length influences sperm transfer by experimental ablation and show that males with shortened processi have significantly reduced post-copulatory reproductive success. Importantly, male insemination func...

The complex, species-specific foreleg armature in males of the genus Themira (Diptera: Sepsidae) provides an ideal system for testing competing hypotheses for the evolution of sexually dimorphic character divergence. In sepsid flies, the male holds onto the female by clasping her wing base with his modified forelegs. In the present study, we document the male leg and the female wing morphology using scanning electron microscopy and confocal microscopy. We use a phylogenetic tree for Themira to reconstruct male foreleg and female wing evolution and demonstrate that the male legs have evolved elaborate structures with little or no corresponding changes in wing morphology. This lack of interspecific variation in female wings is not in agreement with the hypothesis of a morphological ‘evolutionary arms race’ between males and females. However, there is also no evidence for sex-specific wing differences in sensory organs on the wing base that may explain how females could assess males according to Eberhard's ‘cryptic female choice’ hypothesis. Finally, our study reveals the function of several novel morphological clasping structures and documents that the male foreleg characters in Themira are highly homoplastic. Male forelegs in two clades evolve considerably faster than in other species or clades. These two clades include Themira superba and Themira leachi, species that have some of the most dramatically modified forelegs known in Diptera. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 227–238.