Does cooperation mean kinship between spatially discrete ant nests?

Abstract

Eusociality is one of the most complex forms of social organization, characterized by cooperative and reproductive units termed colonies. Altruistic behavior of workers within colonies is explained by inclusive fitness, with indirect fitness benefits accrued by helping kin. Members of a social insect colony are expected to be more closely related to one another than they are to other conspecifics. In many social insects, the colony can extend to multiple socially connected but spatially separate nests (polydomy). Social connections, such as trails between nests, promote cooperation and resource exchange, and we predict that workers from socially connected nests will have higher internest relatedness than those from socially unconnected, and noncooperating, nests. We measure social connections, resource exchange, and internest genetic relatedness in the polydomous wood ant Formica lugubris to test whether (1) socially connected but spatially separate nests cooperate, and (2) high internest relatedness is the underlying driver of this cooperation. Our results show that socially connected nests exhibit movement of workers and resources, which suggests they do cooperate, whereas unconnected nests do not. However, we find no difference in internest genetic relatedness between socially connected and unconnected nest pairs, both show high kinship. Our results suggest that neighboring pairs of connected nests show a social and cooperative distinction, but no genetic distinction. We hypothesize that the loss of a social connection may initiate ecological divergence within colonies. Genetic divergence between neighboring nests may build up only later, as a consequence rather than a cause of colony separation.

Ecological consequences of colony structure in dynamic ant nest networks

“…Wood ants construct nest mounds from pine needles and other material available in the leaf litter. In England, Formica lugubris are polygynous and each nest of the colony is likely to contain multiple queens (Ellis & Robinson, ; Procter et al., ). Scots pine ( Pinus sylvestris ), oak ( Quercus sp .…”

“…An underlying assumption of our measures of both network position properties and colony‐level properties is that the level of traffic on a foraging or internest trail is representative of the quantity of resources (specifically honeydew) being transported along this trail. This assumption is based on data showing that (i) the strength of an internest trail is positively related to the level of foraging being performed at each end of the trail (Ellis et al., ), (ii) 70% of internest journeys involve transport of honeydew (Ellis & Robinson, ), and (iii) the presence of internest trails predicts transport of resources between nests (Procter et al., ).…”

Inter-group cooperation in humans and other animals

“…people can move between groups, but this generally happens less frequently than the time taken to cooperatively produce the resource and exchange it for one from another group worker ants can move between nests, but most show high fidelity to one 'home nest' (e.g. [10]) making groups stable with respect to the timescale of cooperation what resources are shared between groups? many, e.g.…”

Determining social and population structures requires multiple approaches: A case study of the desert antCataglyphis israelensis

“…However, when there is limited dispersal or variation in the basic colony form, such as multiply mated queens (polyandry) or multiple queens (polygyny), these assumptions do not always hold true. In such cases, within‐colony relatedness is very low (Keller, ), and workers from two distinct but neighboring colonies can be more related to each other than to their respective nestmates (Heinze, ; Procter et al, ; Wright, ). It is thus insufficient to assess colony boundaries using genetic methods alone.…”

“…In such cases, within-colony relatedness is very low (Keller, 1993), and workers from two distinct but neighboring colonies can be more related to each other than to their respective nestmates (Heinze, 2008;Procter et al, 2016;Wright, 1943). It is thus insufficient to assess colony boundaries using genetic methods alone.…”