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Polygynandry is a mating system in which both males and females have multiple mating partners during a breeding season. In sexually reproducing diploid animals, different mating strategies are employed by males and females, because the cost of gamete production is lower for males than it is for females. The different mating tactics employed by males and females are thought to be the outcome of stochastic Sexual conflict both ecologically and socially.
Reproductive conflicts in animal societies may arise because individuals are not genetically identical and have different optimal strategies for maximizing their fitness; and often it is found that reproductive conflicts generally arise due to dominance hierarchy in which all or a major part of reproduction is monopolized by only one individual. In the wasp Polistes carolina, the dominant queen amongst female wasps is determined by whoever arrives at the nest first rather than the largest foundress, who is expected to be the best at fighting (wasp). In a study of the bird Prunella collaris, the close proximity and sharing of ranges on the mountain tops of the French Pyrenees led to a polygynandrous mating system, where two to four males would mate with a range of two to four females within the same vicinity.
Polygynandry is another way to describe a multi-male and multi-female polygamous mating system. When females have multiple mating partners, it is known as polyandry, and when males have multiple mating partners, it is known as polygyny. Each sex has potential benefits in being promiscuous; females, especially those with genetically 'inferior' social partners, have the chance to increase the genetic quality of their offspring, while males are able to fertilize the eggs of many other mates. Essentially, the ideal mating behavior for males is to be promiscuous rather than monogamous (when they only have one mating partner), because this leads to multiple offspring, and these males monopolize their female partners by physically preventing them from copulating with other males. On the other hand, females benefit through polyandry, as they have more sired offspring.
To a female, multiple mating means an increase number of young that a female can produce, and oftentimes this also means an increase number of young they have to take care of. In order to ensure the safety and wellbeing of her offspring, females may have multiple mating partners in order to gain more resources from males for herself and her offspring. In dark-eyed juncos, , and , mating with multiple males increases the amount of care a female can gain for her offspring. Oftentimes multiple mates allow females to have more sired offspring and the paternity of the offspring typically falls outside of the biological parents—meaning a different male may look after another male's offspring.
Although males are able to increase their reproductive success faster than females by being able to fertilize eggs faster than females can produce them, males also at a disadvantage when it comes to mating because of sexual selection. Females usually choose males that are 'charming' and those who display sexual ornaments. In a study of long-tailed widowbirds, males with longer tails were sexually selected over those with shorter and less impressive tails. In birds such as the red-collared widowbird, males who display their sexual ornament during courtship are generally paired up faster and attract more females than males who display shorter tails during courtship. Males are often sexually selected based on their physical characteristics and what they have to 'offer', for example, male peacocks with flamboyant colored tails are sexually selected over those with dull and less elaborate tails. Sexual selection of males by females also leads to male-male competition. Unlike females who invest a lot prior to mating, males do not invest as much when generating their sperm, however this increases competition amongst males for female investment. High mating competition also means a greater variance in male success—the best competitors will have better success in mating than those who fail to mate. The best competitors will less likely be inclined to care for their offspring upon mating because they have the ability to produce offspring elsewhere. Males with the greatest size, strength, or best developed weapons achieve the greatest mating success. In other cases, males may have a higher reproductive success if they have better access to resources than other competitors. For instance, female hanging flies mate with a male only if he provides a large insect for her to eat during copulation and North American bullfrogs protect ponds and small lakes where females come to lay their eggs.
Multiple mating by female pycnogonids are possible since a recently mated female often retains unused mature eggs in one or more femora, which allows her to mate with additional partners. In species with external fertilization and male parental care, females are able to distribute her clutch amongst different males and by doing so the female increases the likelihood that at least some of her offspring will receive indirect genetic benefits and/or extensive parental care from a quality provider.
A honey bee queen bee ideally mates with about a dozen drones (males) in her nuptial flight. The sperm of matings are stored in a special reservoir, called the spermatheca, for the life of the queen—which can be several years.
On the other hand, studies have shown that males have had a higher reproductive success than females when they were polygynandrous. When compared to female chimpanzees, male chimpanzees had a better ratio of number of matings and number of offspring produced. Not only did studies show a higher reproductive success, but Columbian ground squirrels exhibited a significant male-biased sexual size and body mass, suggesting male-male competition. Male-male competition means sexual dimorphism amongst the males and this means females are able to sexually select males based on the sexual ornaments they display.
Overall, studies have shown that polygynandry benefits males more than it benefits females. When polygynandry is observed in different species, males most often have the upper hand—meaning males benefit more from polygynandry than do females. Females generally seek multiple mating partners in order to increase benefits for their offspring, whether it be by gaining physical resources for their offspring or by providing their offspring with healthier genes that are fit for survival. On the other hand, in most cases males generally have multiple mating partners in order to obtain as much offspring as they can during their lifespan and they are able to achieve this easier than females because in most cases, males are not parentally involved in caring and raising their offspring.
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