Polygynandry
Polygynandry is a
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
Polygynandry is another way to describe a multi-male and multi-female
Benefits of multiple mating in females
Oftentimes females mate voluntarily with more than one male. Mating with several males reduces the risk of females having unfertilized eggs because one male may not have enough sperm to fertilize all her eggs.[1] In dark-eyed juncos, a female mates with more than one male because oftentimes, her social partner is of lower genetic quality than other potential sperm donors.[3] The females voluntarily mate with other males besides their mate because she sees the potential to improve her offspring viability and sexual attractiveness.[3][1] Females may also mate with several males for genetic benefits such as genetic diversity among her offspring due to the variety of sperm available to her.[1] In song birds, extra-pair matings occur because females are able to sneak away from their home territories to solicit to other males.[1] When female song birds seek extra-male partners, they sexually select males with colorful plumage more elaborate than those of their social partner.[1] Studies show that female song birds that have less plumage partners most actively seek extra-pair matings,[1] furthermore males with the most developed traits—such as longer tails or brighter plumage survive better. Thus, when female song birds have multiple mating partners, they are increasing the genetic quality of their 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.[1] 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.[1] In dark-eyed juncos, dunnocks, and Galapagos hawks, mating with multiple males increases the amount of care a female can gain for her offspring.[3][1] 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.[3]
Benefits of multiple mating in males
Males can potentially fertilize eggs at a much faster rate than females can produce them, meaning a male can best increase his reproductive success by finding and fertilizing as many different females as possible.[1] In Drosophila melanogaster, the reproductive success of males increased with the number of matings, but for females there was no direct relationship with number of mates and number of offspring produced.[1] When males have multiple mating partners, they sometimes have to share parentage of the offspring, reducing the genetic value of the offspring to him and thus reduces the relative benefit of staying to help.[1] When paternity is shared between multiple males, males are expected to be less likely to stay in order to help the female care for the offspring because there is little benefit in staying to help raise the other offspring when there are other males present.[1]
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.[1] In a study of long-tailed widowbirds, males with longer tails were sexually selected over those with shorter and less impressive tails.[1] 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.[1] 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.[1] 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.[1] 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.[1]
Taxonomic references
Amphibia
The various mating tactics are found in a broad number of taxa. In amphibians such as
Pycnogonids (sea spider)
In Ammothea hilgendorfi, a sea spider species, fertilization occurs as a female transfers her eggs to a male who holds them with ovigers, a specialized pair of legs and fertilizes the eggs externally.[5] The males glue the eggs into clusters and carries the eggs on his ovigers until they hatch.[5] The personal cost to males for providing a prolonged care for the young is seen to be a significant parental investment because parental assurance is thought to be substantial for post-zygotic investment.[5] A high level of paternity assurance is Ammothea hilgendorfi, suggests that reduced foraging ability, increased predation risk, and lower mobility exist.[5] An experimental study of Ammothea hilgendorfi showed that although males mate with multiple females, males do not mix egg batches from different dams.[5] The eggs held in clusters by a male hatched in a close time frame, indicating that males mated with different females within a short time span.[5]
Multiple mating by female
Hymenoptera
The reproductive females of social Hymenoptera—wasps, bees, and ants—mate with multiple partners. These females are called queens, to distinguish them from the non-reprodutive females that tend the colony and do not mate.
A honey bee queen 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.
Maintenance
Although promiscuity is said to benefit both males and females, there has not yet been sufficient data to support the fact that promiscuity benefits females. In a study of
On the other hand, studies have shown that males have had a higher reproductive success than females when they were polygynandrous.
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.[3] 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.[2]
References
- ^ a b c d e f g h i j k l m n o p q r s t u Davies, N.B., Krebs, J.R., West, S.A. (2012). An introduction to behavioural ecology, Mating Systems, Chapter 7, 9, 179-222, 254-281.
- ^
- ^ doi:10.1038/479184a
- ^
- ^
- ^ Watson, P.J. (1991). Multiple paternity as genetic bet-hedging in female sierra dome spiders, Linyphia litigiosa (Linyphiidae). Animal Behaviour, 41, 343–360.
- ^ a b c Jones, P. H., Van Zant, J. L., Dobson, F. S. (2012). Variation in reproductive success of male and female Columbian ground squirrels (Urocitellus columbianus), NRC Research Press 90, 736-743.
External links
- The dictionary definition of polygynandry at Wiktionary