Pleometrosis
From Wikipedia, the free encyclopedia
Pleometrosis is a behavior observed in social insects where colony formation is initiated by multiple queens primarily by the same species of insect. This type of behavior has been mainly studied in ants but also occurs in wasps, bees, and termites. This behavior is of significant interest to scientists particularly in ants and termites because nest formation often happens between queens that are unrelated, ruling out the argument of inclusive fitness as the driving force of pleometrosis.[1] In contrast, co-founding queens of wasps and bees are often related.[2] The majority of species that engage in pleometrosis after the initial stages of colony formation will reduce their colonies number of queens down to one dominant queen and either kill or push out the supernumerary queens.[3] However there are some cases where pleometrosis-formed colonies keep multiple queens for longer than the early stages of colony growth.[3] Multiple queens can help to speed a colony through the early stages of colony growth by producing a larger worker ant population faster which helps to out-compete other colonies in colony-dense areas.[3] However forming colonies with multiple queens can also cause intra-colony competition between the queens possibly lowering the likelihood of survival of a queen in a pleometrotic colony.[2]
The driving selection pressure that causes ant species to form colonies through pleometrosis appears to be inter-colony competition in areas with high colony density. When a queen enters an area in which she wants to form a colony, there may be a finite amount of resources to fuel the colony thus necessitating intense competition and territoriality for resources between ant colonies.[2] If the queen forms a colony on her own then she has a low probability of surviving because other colonies may be able to produce workers faster than her or may already be past the early stages of colony formation.[2] Forming the colony on her own could also cause her to have to forage for food to out-compete other colonies through number of offspring. This foraging behavior puts her at risk of predators.[4] However, if she and multiple queens form a colony through pleometrosis they can produce a larger worker force of ants faster and get to a mature reproductive stage of colony growth faster, thus decreasing the chances of death due to inter-colony competition.[2] It has been observed that ants which form pleometrotic colonies engage in less foraging behavior, thus lowering their chance of predation.[4] Having multiple queens cuts down on foraging behavior because each queen uses her own stored energy reserves to feed the brood.[4] By founding the colony pleometrotically ants can form new colonies in high colony density areas and take control of resources in the surrounding area faster. Some genera of ants such as Azteca use the additional worker ants early in the colonies formation to monopolize and take control of resources in close proximity of the colony thus stopping other con-specific colonies from acquiring those resources.[2] This strategy allows the pleometrotic colonies to monopolize the area and starve out competing colonies.[2] The additional worker force in pleometrotic colonies also allows for bigger and more effective brood raids on con-specific colonies which additionally helps to out-compete colonies.[4] A key aspect of founding a colony in a high density colony area is being able to produce a worker force quickly and efficiently so as to not be starved out or robbed of brood from other colonies causing starvation.[2] By engaging in pleometrosis queens increase their chance of survival past the early stages of colony formation due to the increased worker force produced by multiple reproductive individuals. The colony can better control its surrounding resources and effectively compete with other colonies.[2]
