Influence of queen phenotype, investment and maternity apportionment on the outcome of fights in cooperative foundations of the ant Lasius niger

Abstract

Keywords: aggression black garden ant colony founding competition Lasius niger microsatellite pleometrosis reproductive conflict Cooperative colony founding (pleometrosis) in social insects is an ideal model for investigating how cooperation and competition shape social behaviour among unrelated individuals. In many ant species, foundress associations are more competitive and the colonies survive better compared with singlequeen colonies. However, cooperation among queens breaks down at the time of emergence of the first workers, and all but one queen are eliminated. Because no sexuals are produced in incipient colonies, the surviving queen will monopolize the future reproductive success of the colony, while defeated queens will have zero fitness. We examined factors affecting queens' survival prospects during reversion to single-queen colonies in cooperative foundations of the ant Lasius niger. By combining phenotypic and genotypic analyses, we determined how queen's size, individual investment and maternity apportionment influence the outcome of fights. Larger queens were more likely to survive fights. However, smaller queens survived up to one-third of the fighting. By contrast, neither weight loss at the time of a fight outbreak, a measure of queens' relative investment in brood production, nor maternity apportionment influenced the outcome of fights. Moreover, investment of cofoundresses and partitioning of reproduction were not adjusted to queen's size, suggesting that reproductive competition among queens does not occur before the emergence of the first workers. These results lead us to consider pleometrotic associations in L. niger as a 'best of a bad job', whereby the benefits of joint founding and the probability of surviving the conflict might be sufficient for smaller queens to embark on cooperative foundations. Ó

The development of collective personality: the ontogenetic drivers of behavioral variation across groups

“…In eusocial insects, for example, fitness could be measured as the production of new queens and males, but a more accurate measure of fitness would consider the number of new colonies initiated by those new queens (Wilson, 1985). However, the success rate of new queens founding colonies can be low (Aron et al, 2009;Pull et al, 2013), and dependent upon many variables (e.g., climate conditions, predator/parasite density, availability of nesting sites, etc.,) (Voss and Blum, 1987;Tschinkel, 1993;Bernasconi and Keller, 1999). Still, group-level fitness can be measured in multiple ways.…”

Onset of fights and mutual assessment in ant founding queens

“…Upon the emergence of the first workers, queens in most pleometrotic associations engage in fatal fights and all but one queen perishes. In Lasius niger, aggression between reproductives is believed to be decisive for determining which queen survives, and the involvement of workers in fights may only have a marginal influence on the outcome of queen selection (Sommer and Hölldobler, 1995;Aron et al, 2009). Across species, earlier work showed that several factors including queen initial mass, mass loss during foundation, body size, productivity and proximity to the brood influence survival (Aron et al, 2009;Balas and Adams, 1996;Keller, 1996, 1998;Sommer and Hölldobler, 1995).…”

“…In Lasius niger, aggression between reproductives is believed to be decisive for determining which queen survives, and the involvement of workers in fights may only have a marginal influence on the outcome of queen selection (Sommer and Hölldobler, 1995;Aron et al, 2009). Across species, earlier work showed that several factors including queen initial mass, mass loss during foundation, body size, productivity and proximity to the brood influence survival (Aron et al, 2009;Balas and Adams, 1996;Keller, 1996, 1998;Sommer and Hölldobler, 1995). Although these studies provided insights into the mechanisms driving the loss of cooperation in pleometrotic associations, they did not inform on the behavioural rules and information used by queens to start fighting.…”

Selfish strategies and honest signalling: reproductive conflicts in ant queen associations

“…Several studies have attempted to discover the factors that determine which queen survives, with emphasis on testing whether workers assist their mother (e.g. Sommer & Hö lldobler 1995;Bernasconi & Keller 1996;Adams & Balas 1999;Aron et al 2009), although to date such nepotism has not been clearly identified. If workers are incapable of recognizing their mother, they are predicted to favour the most productive queen because she is statistically the most likely to be their mother (Balas 2005).…”

“…Queen ants may lose 20 to 40 per cent of their body weight rearing the first workers (Cahan 2001;Aron et al 2009), so there are likely to be trade-offs between early reproduction and the ability to fight or resist worker aggression. Cofounding queens that anticipate queen elimination may therefore invest less in reproduction than singly founding conspecifics, a prediction that has found empirical support (Bernasconi & Strassmann 1999;Cahan 2001).…”