Female mating decisions: maximizing fitness?

Abstract

Sexual selection theory assumes that maximizing fitness is the ultimate goal in every mating decision. Fitness can be maximized directly by increasing the number of offspring (direct benefits) or indirectly by maximizing offspring's lifetime reproductive success (indirect benefits). Whereas there is considerable evidence in the literature for the influence of mating decisions on direct benefits, indirect benefits have been more elusive. Here, we review the variables that influence mating decisions made by females of freshwater fish and how these affect their fitness directly, as well as indirectly. Females enhance their fitness by matching their mating decisions to current environmental conditions, using a wide range of pre‐ and post‐copulation mechanisms that enable them to maximize benefits from mating. Male sexual traits and courtship displays are signals used by females as a way of assessing male quality in terms of both direct and indirect benefits. Polyandry is very common among freshwater fish species, and indirect benefits have been hypothesized as drivers of its predominance. Despite intensive theoretical work, and multiple suggestions of the effects of indirect benefits, to date no study has been able to demonstrate experimentally the existence of indirect benefits in freshwater fish species. Additionally, most studies of direct benefits measure short‐term benefits of mating decisions. In both cases, lifetime reproductive success is not assessed. Therefore, we are led to conclude that evidence as to whether female mating decisions result in direct and/or indirect benefits in freshwater fish species is still lacking. These results should be considered in light of the ongoing debate about the significance of indirect benefits in female mating decisions.

Extreme sequential polyandry insures against nest failure in a frog

“…A question that now needs to be addressed is whether similar direct benefits could favour polyandry in other animals. Sequential polyandry has been discovered in a diversity of frogs (Backwell & Passmore 1990), fish (Avise et al 2002;Barbosa & Magurran 2006) and birds (Andersson 2005), where males construct nests in unpredictable environments. Whenever possible, females should respond to cues that permit them to optimize their choice of nest site and mating partner, but reliable risk assessment will decrease as environments become increasingly stochastic.…”

A Sea Lamprey (Petromyzon marinus) Sex Pheromone Mixture Increases Trap Catch Relative to a Single Synthesized Component in Specific Environments

“…Because spawning was not observed and our traps were located at migration barriers (no pheromones upstream), our traps were likely the major source of sex pheromones in these streams. Given only two primary sources of sex pheromones at barrier-integrated traps, one complete (SMW) and one incomplete (3kPZS), and a scarcity of potential spawning sites, lampreys may have been more selective concerning pheromone sources (Barbosa and Magurran 2006). The evolution of mate search strategies suggests that, along with mating cues, animals must take into account the costs of time, competition, and use of energy when searching for mates (Real 1990).…”

Phenotype Matching and Early Social Conditions Affect Shoaling and Exploration Decisions

“…Males moving faster into a novel area than females are likely to be a consequence of the differences in the potential reproductive rewards of being bolder in males and females (Wolf et al 2007;King et al 2013). As male guppies have greater variance in reproductive success than females (Houde 1997;Barbosa & Magurran 2006), it is expected that males adopt riskier but potentially high-return behaviours.…”