MICROSATELLITES REVEAL HIGH POPULATION VISCOSITY AND LIMITED DISPERSAL IN THE ANTFORMICA PARALUGUBRIS

Abstract

Abstract.-We used micro satellites to study the fine-scale genetic structure of a highly polygynous and largely unicolonial population of the ant Formica paralugubris. Genetic data indicate that long-distance gene flow between established nests is limited and new queens are primarily recruited from within their natal nest. Most matings occur between nestmates and are random at this level. In the center of the study area, budding and permanent connections between nests result in strong population viscosity, with close nests being more similar genetically than distant nests. In contrast, nests located outside of this supercolony show no isolation by distance, suggesting that they have been initiated by queens that participated in mating flights rather than by budding from nearby nests in our sample population. Recruitment of nestmates as new reproductive individuals and population viscosity in the supercolony increase genetic differentiation between nests. This in turn inflates relatedness estimates among worker nestmates (r = 0.17) above what is due to close pedigree links. Local spatial genetic differentiation may favor the maintenance of altruism when workers raise queens that will disperse on foot and compete with less related queens from neighboring nests or disperse on the wing and compete with unrelated queens.Key words.-Ants, dispersal, Formica, genetic differentiation, microsatellite, population viscosity, queen number, relatedness, social evolution, social insects.Received June 24, 1996. Accepted October 17, 1996.The existence of sterile individuals in social insect colonies poses an evolutionary paradox, namely the difficulty of perpetuating sterility by natural selection when bearers of this trait leave no offspring. An important contribution to the resolution of this puzzle has been provided by Hamilton (1963, I964a,b), who showed that individuals can pass on copies of their genes to the next generation not only by producing offspring, but also by helping nondescendent kin, such as siblings.Colonies of social insects typically consist of related individuals, a necessary condition for kin selection to operate. However, nests of some ant and wasp species contain a high number of queens, which has the effect that nestmates are only distantly related (e.g., Sturtevant 1938; Queller et al.

Population genetics of the socially polymorphic ant Formica podzolica

“…Furthermore, we found no strong evidence for isolation by distance among colonies within sites. Other studies of polygynous Formica (Chapuisat et al, 1997;Pirk et al, 2001) and even some weakly polygynous ants (Fournier et al, 2002) have reported correlations of distance and genetic differentiation that were many times larger than the values we found in this system. Thus, F. podzolica shows substantially weaker within-population subdivision than other polygynous or socially polymorphic Formica species.…”

Allozyme variability and differentiation in Serbian roe deer populationsCapreolus capreolus

“…This estimator is not bounded between 0 and 1. When the population is structured, relatc adequately removes the increase in relatedness due to this structuring (see Chapuisat et al 1997, for an example).…”

Nest site selection and longevity in the ponerine ant Rhytidoponera metallica (Hymenoptera, Formicidae)

“…Colony formation can also occur via budding, (e.g. Chapuisat et al, 1997;Chapuisat and Crozier, 2001) in which workers apparently choose the new nest site. Nest relocations after colony formation are common in some species (Smallwood and Culver, 1979;Smallwood, 1982;Briano et al, 1995;Byrne, 1994;Banschbach and Herbers, 1999), and are thought to be a response to intolerable nest conditions and/or locating a more favorable nest site (Smallwood, 1982;Tinaut et al, 1999).…”