Polydomy enhances foraging performance in ant colonies

Abstract

Collective foraging confers benefits in terms of reduced predation risk and access to social information, but it heightens local competition when resources are limited. In social insects, resource limitation has been suggested as a possible cause for the typical decrease in per capita productivity observed with increasing colony size, a phenomenon known as Michener's paradox. Polydomy (distribution of a colony's brood and workers across multiple nests) is believed to help circumvent this paradox through its positive effect on foraging efficiency, but there is still little supporting evidence for this hypothesis. Here, we show experimentally that polydomy enhances the foraging performance of food-deprived Temnothorax nylanderi ant colonies via several mechanisms. First, polydomy influences task allocation within colonies, resulting in faster retrieval of protein resources. Second, communication between sister nests reduces search times for far away resources. Third, colonies move queens, brood and workers across available nest sites in response to spatial heterogeneities in protein and carbohydrate resources. This suggests that polydomy represents a flexible mechanism for space occupancy, helping ant colonies adjust to the environment.

Symmetry breaking and pivotal individuals during the reunification of ant colonies

“…Indeed, colonies were just as likely to reunify with symmetric as for asymmetric splits. This ability is potentially useful if, like some other Temnothorax species, T. rugatulus is seasonally polydomous, periodically recoalescing from multiple nests (Alloway et al, 1982;Cao, 2013;Partridge et al, 1997;Roberts et al, 1999;Stroeymeyt et al, 2017). Symmetry breaking could also be useful during emigration if colonies transiently split among many similar locations, eventually reuniting at a single one.…”

“…The first goal of this study was to determine whether T. rugatulus colonies can reunify after symmetric divisions; that is, when they are evenly divided between identical nests, neither of which contains a queen. Such splits may occur in nature if T. rugatulus, like other Temnothorax species, fractionates between multiple nests in spring and recoalesces at one site in autumn (Alloway et al, 1982;Cao, 2013;Partridge et al, 1997;Roberts et al, 1999;Stroeymeyt et al, 2017). Temnothorax colonies in the wild may occupy three or more nests at one time (Alloway et al, 1982), and recoalescence therefore plausibly occurs in stages and involves unions between queenless groups inhabiting similar nests.…”

Multiple nest entrances alter foraging and information transfer in ants

“…Furthermore, multiple nest entrances may be advantageous by covering a wider foraging area, spreading out more evenly foragers across their home range and thereby maximizing food encounter rates, particularly for scattered food items [49]. Finally, in the case of polydomy, where each entrance is specifically connected to a subunit of the colony, supplementary entrances will enhance foraging efficiency, as they will favour the division of labour and thus, the efficiency of food exploitation at the colony level [50].…”

Occurrence of Ants (Hymenoptera: Formicidae) in both Leaf Litter and Twigs in Atlantic Forest

“…The polydomous colony is a functional and cooperative unit (Ellis et al, 2017), because it increases the probability of colony survival (Silvestre et al, 2003;Santos & Del-Claro, 2009) by expanding the foraging area (Robinson, 2014) and the space for colony development (Byrne, 1994) in the competitive environment of the leaf litter (Yanoviak & Kaspari, 2000). In addition, it protects the colony against predators (Debout et al, 2007) by facilitating information sharing, such as mass recruitment (Hamidi et al, 2017) and transfer of immatures and the queen (Stroeymeyt et al, 2017). A polydomous colony structure is a strategy to reduce mortality, because this risk increases when there is only one nest (Hölldobler & Wilson, 1990;Debout et al, 2007).…”