Polydomy : the organisation and adaptive function of complex nest systems in ants

Many ant species spread their colonies between multiple spatially separated but socially connected nests, a phenomenon known as polydomy. Polydomous species are ecologically and phylogenetically diverse, and often economically significant as invasive pests. Benefits of polydomy may include risk spreading, efficient resource exploitation and ergonomic factors. Very little is known about the costs of polydomy; facultatively polydomous species are good candidates for identifying costs. Analysing polydomous colony structure provides insights into which costs and benefits are driving the colony organisation; for example, a cross-species analysis of inter-nest trail networks shows structural features related to long-distance transport efficiency. Deeper understanding of polydomy will shed light on key issues in evolutionary and behavioural ecology, and also benefit both conservation and pest control

Internest food sharing within wood ant colonies : resource redistribution behavior in a complex system

Resource sharing is an important cooperative behavior in many animals. Sharing resources is particularly important in social insect societies, as division of labor often results in most individuals including, importantly, the reproductives, relying on other members of the colony to provide resources. Sharing resources between individuals is therefore fundamental to the success of social insects. Resource sharing is complicated if a colony inhabits several spatially separated nests, a nesting strategy common in many ant species. Resources must be shared not only between individuals in a single nest but also between nests. We investigated the behaviors facilitating resource redistribution between nests in a dispersed-nesting population of wood ant Formica lugubris. We marked ants, in the field, as they transported resources along the trails between nests of a colony, to investigate how the behavior of individual workers relates to colony-level resource exchange. We found that workers from a particular nest “forage” to other nests in the colony, treating them as food sources. Workers treating other nests as food sources means that simple, pre-existing foraging behaviors are used to move resources through a distributed system. It may be that this simple behavioral mechanism facilitates the evolution of this complex life-history strategy

Keeping invertebrate research ethical in a landscape of shifting public opinion

(1) Invertebrate study systems are cornerstones of biological and biomedical research, providing key insights into fields from genetics to behavioural ecology. Despite the widespread use of invertebrates in research there are very few ethical guidelines surrounding their use. (2) Focussing on two ethical considerations faced during invertebrate studies – collecting methods and euthanasia - we make recommendations for integrating principles of vertebrate research into invertebrate research practice. (3) We argue, given emerging research on invertebrate cognition and shifting public perception on the use of invertebrates in research, it is vital that the scientific community revisits the ethics of invertebrate use in research. (4) Without careful consideration and development of the ethics surrounding the use of invertebrates by the scientific community, there is a danger of losing public support. It is imperative that the public understand the significance of research that uses invertebrates and that scientists demonstrate their ethical treatment of their experimental subjects

Inferring polydomy : a review of spatial, functional and genetic methods for identifying colony boundaries

Identifying the boundaries of a social insect colony is vital for properly understanding its ecological function and evolution. Many species of ants are polydomous: colonies inhabit multiple, spatially separated, nests. Ascertaining which nests are parts of the same colony is an important consideration when studying polydomous populations. In this paper, we review the methods that are used to identify which nests are parts of the same polydomous colony and to determine the boundaries of colonies. Specifically, we define and discuss three broad categories of approach: identifying nests sharing resources, identifying nests sharing space, and identifying nests sharing genes. For each of these approaches, we review the theoretical basis, the limitations of the approach and the methods that can be used to implement it. We argue that all three broad approaches have merits and weaknesses, and provide a methodological comparison to help researchers select the tool appropriate for the biological question they are investigating

Does cooperation mean kinship between spatially discrete ant nests?

Procter, D., J. Cottrell, K. Watts, S. A'Hara, M. Hofreiter and E. J. H. Robinson (in press). "" Ecology and Evolutio

Do non-native conifer plantations provide benefits for a native forest specialist, the wood ant Formica lugubris?

AbstractRecent increases in plantation forestry are starting to reverse the global decline in forest cover, in some areas of the world. Britain has practiced afforestation, primarily with non-native conifers, for over a century. It is unclear whether these new plantations have the potential to support native forest species.We quantify afforestation across the North York Moors National Park, UK, deriving a chronology of afforestation from historic maps at six time points from 1854 to 2013. We map the location of current wood ant (Formica lugubris) nests and set their distribution in the context of historic forest cover. We use these nest locations and the features of the habitat in which they occur to model the suitability of recently established conifer plantations for wood ants using MaxEnt. We determine whether non-native conifers offer suitable habitat for a forest specialist species, and assess the lag between establishment of conifer plantations and colonisation by wood ants from historic woodland fragments.Forest cover increased by 229% over 160years and is now dominated by non-native conifer plantations. Our survey data show that current wood ant populations extend hundreds of metres from where forest was in the past, demonstrating geographical population expansions into newly formed forest, comprised of non-native conifer plantations. Both our data and model reveal that the recently planted non-native conifer plantations are a suitable habitat for this forest specialist species. Our model reveals that Formica lugubris has not yet spread through all available suitable habitat due to very poor dispersal ability, displaying a severe lag behind the availability of habitat.Managers should not assume that unoccupied habitat is unsuitable nor should they expect to see immediate colonisation of plantations. Future forest creation should be targeted close to existing forests to facilitate colonisation of forest specialists

How collective comparisons emerge without individual comparisons of the options

Collective decisions in animal groups emerge from the actions of individuals who are unlikely to have global information. Comparative assessment of options can be valuable in decision-making. Ant colonies are excellent collective decision-makers, for example when selecting a new nest-site. Here, we test the dependency of this cooperative process on comparisons conducted by individual ants. We presented ant colonies with a choice between new nests: one good and one poor. Using individually radio-tagged ants and an automated system of doors, we manipulated individual-level access to information: ants visiting the good nest were barred from visiting the poor one and vice versa. Thus, no ant could individually compare the available options. Despite this, colonies still emigrated quickly and accurately when comparisons were prevented. Individual-level rules facilitated this behavioural robustness: ants allowed to experience only the poor nest subsequently searched more. Intriguingly, some ants appeared particularly discriminating across emigrations under both treatments, suggesting they had stable, high nest acceptance thresholds. Overall, our results show how a colony of ants, as a cognitive entity, can compare two options that are not both accessible by any individual ant. Our findings illustrate a collective decision process that is robust to differences in individual access to information

The Evolution of Intergroup Cooperation

Sociality is widespread among animals, and involves complex relationships within and between social groups. While intra-group interactions are often cooperative, intergroup interactions typically involve conflict, or at best tolerance. Active cooperation between members of distinct, separate groups occurs very rarely, predominantly in some primate and ant species. Here we ask why intergroup cooperation is so rare, and what conditions favour its evolution. We present a model incorporating intra- and intergroup relationships and local and long-distance dispersal. We show that dispersal modes play a pivotal role in the evolution of intergroup interactions. Both long-distance and local dispersal processes drive population social structure, and the costs and benefits of intergroup conflict, tolerance and cooperation. Overall, the evolution of multi-group interaction patterns including both intergroup aggression and intergroup tolerance, or even altruism, is more likely with mostly localised dispersal. However, the evolution of these intergroup relationships may have significant ecological impacts, and this feedback may alter the ecological conditions that favour its own evolution. These results show that the evolution of intergroup cooperation is favoured by a specific set of conditions, and may not be evolutionarily stable. We discuss how our results relate to empirical evidence of intergroup cooperation in ants and primates