Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata

Abstract

Colonies of the primitively eusocial wasp Ropalidia marginata consist of a single egg layer (queen) and a number of non-egg-laying workers. Although the queen is a docile individual, not at the top of the behavioral dominance hierarchy of the colony, she maintains complete reproductive monopoly. If the queen is lost or removed, one and only one of the workers [potential queen (PQ)] becomes hyperaggressive and will become the next queen of the colony. The PQ is almost never challenged because she first becomes hyperaggressive and then gradually loses her aggression, develops her ovaries, and starts laying eggs. Although we are unable to identify the PQ when the queen is present, she appears to be a "cryptic heir designate." Here, we show that there is not just one heir designate but a long reproductive queue and that PQs take over the role of egg-laying, successively, without overt conflict, as the queen or previous PQs are removed. The dominance rank of an individual is not a significant predictor of its position in the succession hierarchy. The age of an individual is a significant predictor, but it is not a perfect predictor because PQs often bypass older individuals to become successors. We suggest that such a predesignated reproductive queue that is implemented without overt conflict is adaptive in the tropics, where conspecific usurpers from outside the colony, which can take advantage of the anarchy prevailing in a queenless colony and invade it, are likely to be present throughout the year.reproductive conflict | reproductive succession | eusociality | cooperative breeding | insect societies R eproductive division of labor is the hallmark of insect societies. This is achieved by the differentiation of colony members into reproductive (queen/king) and nonreproductive (worker) castes (1, 2). In insect societies such as those of ants, honeybees, swarm-founding wasps, and higher termites, which are traditionally referred to as highly eusocial, caste determination is achieved by preimaginal physiological processes that channel individuals into distinct reproductive or worker developmental pathways. Thus, caste of an individual is already determined at the time of eclosion and remains irreversible. If the reproductive dies, the colony has to rear a new one from the egg or early larval stage because the workers cannot change their caste in adulthood. In societies such as those of most social bees and wasps, which are traditionally referred to as primitively eusocial, all adult colony members are nearly totipotent and morphologically similar. The process of caste differentiation into reproductives and nonreproductives takes place largely in the adult stage and is based on social interactions among colony members (3-9). This makes the castes flexible and often reversible, so that workers can become queens upon the loss or death of the original queen. In addition to indirect fitness gained as workers, individuals, thus, also have a finite probability of direct reproduction as future queens. Similarly in wood-dwelli...

The evolution of eusociality: no risk‐return tradeoff but the ecology matters

“…assumed, queen death may sometimes lead to a temporary slow‐down in offspring production while workers compete to become the new queen. In some primitively eusocial taxa, a gerontocratic inheritance system where the new queen is always the oldest surviving female may largely avoid conflict during queen replacement (Bridge & Field ; see also Bang & Gadagkar ). However, Strassmann et al .…”

Multiple Aggressions Among Nestmates Lead to Weak Dominance Hampering Primitively Eusocial Behaviour in an Orchid Bee

“…In the majority of species with totipotent individuals, reproductive dominance (queen-like vs worker-like females) and behavioural dominance (aggressive vs less aggressive individuals) can be predicted as it is usually the older or the bigger individual in the colony (Schwarz, 1994). Nevertheless it is not always easy to assign hierarchies for totipotent females since they can present a cryptic hierarchy (Bang & Gadagkar, 2012). Furthermore in many totipotent social Hymenoptera species, both queen-like and worker-like females are breeders (Andrade-Silva & Nascimento, 2012;Schwarz et al, 2007) and they both mate and produce offspring (sons and daughters) hence as the relatedness in the colony decreases, nestmates face more reproductive competition (Langer et al, 2004).…”

Homing abilities of the tropical primitively eusocial paper wasp Ropalidia marginata

“…No wasps may have returned from outside the maximal homing area either because they were genuinely lost or because even the navigational ability of the individuals may not make it possible for them to return from such a large distance soon enough so as not to face the risk of starvation and/or lose their status on their previous nest; if it thus takes too long, they may find it more profitable to initiate their own nest. Unlike the sterile workers of honeybees and stingless bees, who have no option of starting their own new nests and who have no danger of losing their status on their nests, R. marginata foragers are capable of initiating their own nests (Gadagkar 2001) and are also susceptible to losing their status on their nests (Bang and Gadagkar 2012). This may account for why these wasps do not return from as large distances as many of the bee workers do (Chmurzyński et al 1998;Goulson and Stout 2001;Pahl et al 2011;Roubik and Aluja 1983;Visscher and Seeley 1982).…”