Colony Budding and its Effects on Food Allocation in the Highly Polygynous Ant, Monomorium pharaonis

Abstract

To advance our understanding of the causes and the consequences of budding (colony multiplication by fragmentation of main nests), we investigated nest movement in the facultatively polydomous Pharaoh ant, Monomorium pharaonis. Demographic data revealed that Pharaoh ants are highly polygynous and have a relatively low worker to queen ratio of 12.86. Budding experiments demonstrated that the number of available bud nests has a significant effect on colony fragmentation and increasing the number of bud nests resulted in smaller colony fragments. The overall distribution among bud nests was uneven, even though there was no evidence that the different life stages and castes partitioned unevenly among the bud nests and the analysis of individual colonies revealed no evidence of an uneven split in any of the colonies. This demonstrates that Pharaoh ants have the ability to exert social control over colony size and caste proportions during budding, which may contribute to their success as an invasive ant. The intensity of nest disturbance had a significant effect on whether or not the ants migrated into bud nests. Major disturbance resulted in the ants abandoning the source nest and migrating to bud nests and minor disturbance did not stimulate the ants to abandon the source nest. The results of the successive budding experiment which allowed the ants the opportunity to bud into progressively smaller nest fragments demonstrate that Pharaoh ants maintain a preferred minimum group size of 469 ± 28 individuals. Food allocation experiments utilizing protein marking revealed that nest fragmentation in Pharaoh ants has no negative impact on intracolony food distribution. Overall, our results suggest that nest units in the Pharaoh ant behave like cooperative, rather than competitive, entities. Such cooperation is most likely facilitated by the fact that individuals in all bud nests are genetically related, remain in close proximity to each other, and may continue to exchange individuals after budding.

Polydomy enhances foraging performance in ant colonies

“…Similarly, most support for the foraging benefits of dispersed central-place foraging derives from models [25,27,34] and observations that polydomous colonies establish new nests near stable food sources [22][23][24]33,36,[38][39][40]. Few studies have attempted to quantify the foraging efficiency of polydomous ant colonies [5,6,24,26,38,45], and even fewer used experimental manipulations to evaluate the effect of nest number on foraging efficiency [5,45].…”

Suburban sprawl: environmental features affect colony social and spatial structure in the black carpenter ant, Camponotus pennsylvanicus

“…Numerous factors such as physical deterioration of nesting structure, competition with other animals, exhaustion of food supplies, seasonal polydomy, or discovery of more attractive nesting sites may be driving the shift in nesting strategies. In other cases, ants move their nests to avoid predation (Droual, 1984; Yamaguchi, 1992; McGlynn et al , 2004; Dahbi et al , 2008), to escape from unfavourable environmental conditions (Yamaguchi, 1992; Gibb & Hochuli, 2003), to increase access to food (McGlynn et al , 2004), to maximise foraging efficiency (Holway & Case, 2000), or to avoid overcrowding (Gobin et al , 1998; Buczkowski & Bennett, 2009). Camponotus pennsylvanicus nests are generally found in live trees and most likely remain in good physical condition throughout the life of the colony.…”

“…red imported fire ants: Tschinkel et al , 1995), colony reproduction by budding (e.g. Pharaoh ants: Buczkowski & Bennett, 2009), or even intracolony competition for resources (e.g. odorous house ants: Buczkowski & Bennett, 2006).…”

Exotic ants (Hymenoptera, Formicidae) of Ohio

“…In northern temperate regions, this small ant is highly synanthropic and depends on humans for food and shelter (Buczkowski and Bennett 2009). In Ohio, it is known only from people's homes and other heated buildings.…”

“…A major contributing factor to the invasiveness of this ant is the formation of daughter colonies via fragmentation of the main nest. Newly formed nests remain in contact with the natal nest and may continue to exchange individuals after budding (Buczkowski and Bennett 2009). This results in large polydomous colonies that can quickly monopolize available resources.…”