Male intrasexual competition
In
Influencing factors
Sex ratio
There are multiple types of male-male competition that may occur in a population at different times depending on the conditions. Competition variation occurs based on the frequency of various mating behaviours present in the population.[1] One factor that can influence the type of competition observed is the population density of males.[1] When there is a high density of males present in the population, competition tends to be less aggressive and therefore sneak tactics and disruptions techniques are more often employed.[1] These techniques often indicate a type of competition referred to as scramble competition.[1] In Japanese medaka, Oryzias latipes, sneaking behaviours refer to when a male interrupts a mating pair during copulation by grasping on to either the male or the female and releasing their own sperm in the hopes of being the one to fertilize the female.[1] Disruption is a technique which involves one male bumping the male that is copulating with the female away just before his sperm is released and the eggs are fertilized.[1]
However, all techniques are not equally successful when in competition for reproductive success. Disruption results in a shorter copulation period and can therefore disrupt the fertilization of the eggs by the sperm, which frequently results in lower rates of fertilization and smaller clutch size.[1]
Resource value and social ranking
Another factor that can influence male-male competition is the value of the resource to competitors. Male-male competition can pose many risks to a male's fitness, such as high energy expenditure, physical injury, lower sperm quality and lost paternity.
Winner–loser effects
A third factor that can impact the success of a male in competition is winner-loser effects.[6] Burrowing crickets, Velarifictorus aspersus, compete for burrows to attract females using their large mandibles for fighting.[6] Female burrowing crickets are more likely to choose winner of a competition in the 2 hours after the fight.[6] The presence of a winning male suppresses mating behaviours of the losing males because the winning male tends to produce more frequent and enhanced mating calls in this period of time.[6]
Effect on female fitness
Male-male competition can both positively and negatively affect female fitness. When there is a high density of males in a population and a large number of males attempting to mate with the female, she is more likely to resist mating attempts, resulting in lower fertilization rates.[1] High levels of male-male competition can also result in a reduction in female investment in mating.[4] Many forms of competition can also cause significant distress for the female negatively impacting her ability to reproduce.[1] An increase in male-male competition can affect a female's ability to select the best mates, and therefore decrease the likelihood of successful reproduction.[7]
However, group mating in Japanese medaka increases the fitness of females due to an increase in genetic variation, a higher likelihood of paternal care, and a higher likelihood of successful fertilization.[1] Exposure to environmental estrogens, such as some herbicides, can confuse female choice of males.[8]
See also
References
- ^ S2CID 15410498.
- ^ S2CID 594384.
- S2CID 53188298.
- ^ S2CID 15032582.
- S2CID 13912038.
- ^ PMID 29946077.
- .
- ^ McCallum, M.L., M. Matlock, J. Treas, B. Safi, W. Sanson, J.L. McCallum. (2013). Endocrine disruption of sexual selection by an estrogenic herbicide in Tenebrio molitor. Ecotoxicology 22:1461-1466.