Table 1.

Summary of potential conflicts mediated by SFPs

Trait over which there is potential conflict	Nature of the potential conflict	Types of SFPs that are potentially responsible for the conflict
Remating	Conflict over remating may occur between a female and her previous mates and between a mated female and courting males. Remating may benefit the female but at a cost to her previous mates because there are potential benefits for females of topping up or receiving better- quality, fresh sperm. These benefits may be at odds with the interests of males whose sperm are already in storage. There are also potential conflicts arising from the deleterious effects of male–male sperm competition. Yet, extensive remating could be costly to a female but beneficial to the males attempting to mate with her.	Those that modulate female receptivity, attractiveness, activity levels, pheromone production, and emission
Sperm transfer, storage, retention, usage	Conflict may arise over how many sperm are transferred during mating, stored by the female, and released for fertilization. The interests of the sexes over the efficiency of individual sperm usage should be aligned. However, sperm usage may become inefficient as a result of elevated rates of egg production, over which there is separate potential conflict, see below.	Those that mediate sperm transfer, sperm storage, sperm competition, the musculature of the female reproductive tract, including the sperm storage organs
Egg production, ovulation, egg provisioning, oviposition	Males may often gain from elevating current egg-production or egg-provisioning rates more than is the case for females. Females may trade off current versus future investment and gain from a longer-term strategy. Males, on the other hand, may gain from increased current investment by the female, despite any future costs. Any divergence over the rate of ovulation may negatively impact the efficiency of fertilization, as noted above.	Those that mediate ovulation, release of reproductive hormones, egg production, and provisioning
Food intake	Females may need to increase or change their nutrient intake to support increased reproductive rate. This will be favored in an open-ended way by males, who may have little interest in any future costs that the female might incur. However, increased nutrient trafficking decreases female life span, thus representing potential sexual conflict in terms of a female’s future reproductive capacity.	Those that mediate feeding behavior and nutrient balancing
Activity	The female’s sleep/wake cycles can be altered by SFPs and could impact energy usage. Increased activity and reduced siesta sleep in females (e.g., in Drosophila) could incur long-term costs for females but not males, reflecting a potential conflict.	Those that mediate activity patterns and circadian rhythms
Immune activation	Striking changes to the immune system occur during reproduction, the significance of which is not yet globally clear. However, there is potential for conflict if there is a suboptimal under- or overexpression of immunity in the female, with immune activity traded off against future reproductive capacity.	SFPs that have antimicrobial activity or that cause the expression of immune genes in females
Life span	SFPs that reduce female life span can be selected because any cost is incurred in the future. Therefore, the effect of such costs is felt unequally by males and females.	SFPs that either directly or indirectly exert costs leading to reduced female life span