Dispersal of first “workers” in social wasps: Causes and implications of an alternative reproductive strategy

Abstract

Many ''workers'' in north temperate colonies of the eusocial paper wasp Polistes fuscatus disappear within a few days of eclosion. We provide evidence that these females are pursuing an alternative reproductive strategy, i.e., dispersing to overwinter and become nest foundresses the following spring, instead of helping to rear brood on their natal nests. A female is most likely to stay and help at the natal nest (i.e., least likely to disperse) when it is among the first workers to emerge and when it emerges on a nest with more pupae (even though worker-brood relatedness tends to be lower in such colonies). The latter cause may result from the fact that pupae-laden nests are especially likely to survive, and thus any direct or indirect reproductive payoffs for staying and working are less likely to be lost. Disappearing females are significantly smaller than predicted if dispersal tendency was independent of body size (emergence order-controlled), suggesting that the females likely to be most effective at challenging for reproductive rights within the natal colony (i.e., the largest females) are also most likely to stay. Thus, early dispersal is conditional on a female's emergence order, the maturity of its natal nest, and its body size. Finally, we present evidence that foundresses may actively limit the sizes of first-emerging females, perhaps to decrease the probability that the latter can effectively challenge foundresses for reproductive rights. The degree to which foundresses limit the size of first-emerging females accords well with the predictions of the theory of staying incentives.

Conflict Resolution in Insect Societies

“…Attempts by high-ranking workers (hopeful reproductives) to overthrow the existing breeder have been observed in the queenless ant Dinoponera quadriceps (74, 77). Evidence that females in annual societies leave the colony early to become a queen the next year comes from the sweat bee Halictus rubicundus (146) and the paper wasps Polistes annularis (116) and Polistes fuscatus (104).…”

“…That is, in the face of reproductive competition with sisters, a female benefits if she becomes a breeder and produces offspring (sons and daughters, r = 0.5) rather than a worker rearing the less-related offspring of sisters (nephews and nieces, r = 0.375) (76, 77). Actual conflict can result in an excess of females attempting to mate and breed (67), in females attempting to overthrow the existing queen (76, 77), or, in annual societies, in females leaving the colony early in order to enter diapause to found a colony the next year (104,116,146). …”

“…RATNIEKS FOSTER WENSELEERS it cannot prevent females from breeding by leaving the nest completely to become a queen the next year (104,116,146). Another form of coercion in conflicts among totipotent individuals is social contracts, which are thought to be important in favoring the cofounding of nests when there is inequality among the foundresses (103).…”

Genetic support for the evolutionary theory of reproductive transactions in social wasps

“…A linear dominance hierarchy develops among these foundresses and the most dominant foundress (alpha) produces most but not all of the eggs. In Polistes fuscatus the ¢rst brood develops into early females, some of which become workers (which sometimes reproduce as replacement queens; Klahn 1981) but many or most of which leave the nest to become foundresses the following year (Reeve et al 1998b). Later brood develop into males and late females, the latter also becoming part of next year's pool of foundresses (West-Eberhard 1969;Noonan 1981).…”

A diapause pathway underlies the gyne phenotype inPolisteswasps, revealing an evolutionary route to caste-containing insect societies

“…6), which often coincides with behavioral quiescence (20), has been speculated to underlie characteristics of gyne offspring in the paper wasp genus Polistes (21-24), a social insect that lacks discrete morphological castes (25). However, the occurrence of early gynes (26) and late workers (27) in Polistes (5) argues against the role of conventional ambient variables, such as photoperiod or temperature, as diapause cues in this taxon. Instead, experimental evidence points to nourishment: low vs. high food levels during rearing in a common laboratory environment led to putative worker and gyne phenotypes, respectively, as confirmed by differential survival of a cold test (28,29).…”