The evolution of polyandry : multiple mating and female fitness in insects

Female Drosophila melanogaster were maintained at five levels of nutrition, with either continuous or intermittent exposure to males. Remating frequency increased with nutrition and was higher with continuous exposure to males. Age-specific and lifetime egg production increased with increasing nutrition, but lifespan peaked at intermediate nutrition. Females on the three highest nutritional levels showed a cost of mating in reduced survival, but only at the highest food level did this reduced lifespan lead to a significant cost of mating for lifetime egg production. The data suggest that remating frequencies in laboratory cultures may evolve to a low enough level for the cost of mating to be only weakly expressed, if at all. Further data are required to assess the importance of the cost of mating in natural populations, where the evolution of low remating frequencies might be expected to be opposed by other costs.

Female fitness in Drosophila melanogaster: an interaction between the effect of nutrition and of encounter rate with males.

In Drosophila simulans a Wolbachia-like microorganism is responsible for reduced egg-hatch when infected males mate with uninfected females. Both incompatibility types have previously been found in North America, Europe and Africa. Some California populations have remained polymorphic for over two years, and the infection is apparently spreading in central California. Egg hatch proportions for wild-caught females from polymorphic populations show that the incompatibility system acts in nature, but egg mortality rates are apparently lower than observed in laboratory populations. Although infected females maintained under various laboratory conditions never produce uninfected offspring, some wild-caught infected females produce both infected and uninfected progeny. This helps explain the persistence of a low frequency of uninfected flies in predominantly infected populations and may also explain the other polymorphisms observed. Fitness comparisons of infected and uninfected stocks, including both larval and adult fitness components, indicate that fecundity may be the component most affected. Infected females suffer a fecundity reduction of 10-20% in the laboratory, but the reduction seems to be smaller in nature. A theoretical analysis provides some insight into the population biology of the infection.

https://www.genetics.org/content/genetics/126/4/933.full.pdf

Factors affecting the distribution of cytoplasmic incompatibility in Drosophila simulans.

Successful reproduction requires contributions from both the male and the female. In Drosophila, contributions from the male include accessory gland proteins (Acps) that are components of the seminal fluid. Upon their transfer to the female, Acps affect the female's physiology and behavior. Although primary sequences of Acp genes exhibit variation among species and genera, the conservation of protein biochemical classes in the seminal fluid suggests a conservation of functions. Bioinformatics coupled with molecular and genetic tools available for Drosophila melanogaster has expanded the functional analysis of Acps in recent years to the genomic/proteomic scale. Molecular interplay between Acps and the female enhances her egg production, reduces her receptivity to remating, alters her immune response and feeding behavior, facilitates storage and utilization of sperm in the female and affects her longevity. Here, we provide an overview of the D. melanogaster Acps and integrate the results from several studies that bring the current number of known D. melanogaster Acps to 112. We then discuss several examples of how the female's physiological processes and behaviors are mediated by interactions between Acps and the female. Understanding how Acps elicit particular female responses will provide insights into reproductive biology and chemical communication, tools for analyzing models of sexual cooperation and/or sexual conflict, and information potentially useful for strategies for managing insect pests.

Seminal influences: Drosophila Acps and the molecular interplay between males and females during reproduction

Multiple mating by females: a perspective from quantitative genetics

As a consequence of copulation, males of Drosophila melanogaster induce a variety of physiological and behavioral effects in the female. Egg production and oviposition are stimulated by products of the male's accessory glands (Kummer, 1960; Garcia-Bellido, 1964; Merle, 1968; Bumet et al., 1973), and female attractiveness and receptivity are both reduced following copulation. Changes in female attractiveness are mediated pheromonally. A change in pheromonal profile from courtship-eliciting to courtship-discouraging pheromones is induced during the first 3 min of copulation (Tompkins et al., 1980; Tompkins and Hall, 1981; Venard and Jallon, 1980). The seminal fluid enzyme esterase-6 metabolizes the seminal fluid component cis-vaccenyl acetate to produce the antiaphrodisiac cis-vaccenyl alcohol (Mane et al., 1983). Behavioral effects of this metabolite on female attractiveness have been demonstrated and have been shown to be short-lived. There is a close correspondence between the time course of these behavioral effects and those first identified by Manning (1967) as the "copulation effect." Manning (1962, 1967) also identified a "sperm effect" on female receptivity which is longer lasting and causes females to remain unreceptive to male courtship. The strength of the sperm effect seems to be proportional to the number of sperm in storage (Gromko and Pyle, 1978; Gromko et al., 1984). The sperm effect is characterized behaviorally by the use of ovipositor extrusion to reject males, a behavior used only in very low frequency by virgin females (Connolly and Cook, 1973; Tompkins and Hall, 1981). The "sperm effect" -or the sperm dependence of the return of female receptivity-is not evident when mated females are confined with second males continuously for 24 h (Newport and Gromko, 1984). In this paper we investigate the details of the sperm dependence of female receptivity within the context of an experimental design which allows females periodic interactions with second males. We also quantify the impact of sperm-dependent female receptivity on the reproductive outcome of double matings. We show that by causing females to delay remating, first males suffer very little reduction in reproductive success due to female remating.

Maria G. Kortier

Papers

Sperm dependence of female receptivity to remating in drosophila melanogaster.