An analysis of the dynamics of resource sharing networks in ant colonies

Cooperation ties animals together into social groups that often demonstrate complex emergent behaviours. One striking example of this are social insect societies that emerge from extreme cooperative behaviour and have an important impact in many ecosystems. Colonies of most social insects construct and inhabit a single nest. However, colonies of some species have been found to spread across many different nests – known as polydomy. This strategy is thought to have evolved in response to several different drivers, such as increased foraging efficiency, avoiding nest-size limitations and territory defence. In this thesis, I present studies that investigated how polydomous colonies function and the reasons that some, but not all, ant species use polydomy as a strategy. I used a mathematical model to demonstrate that decentralization of the nest population can be advantageous under a variety of different conditions, which explains why polydomous species are so behaviourally and phylogenetically diverse. Using a longitudinal study of several years of data on a set of polydomous colonies I found that resource sharing networks become more static over a season and that while nest foundation occurs throughout the season, nest abandonment occurs at a much faster rate in the latter part of the season. Through sampling several polydomous colonies, I found that there is a correlation between relatedness of the inhabitants of different nests and the rate of resource sharing between the nests. The most likely mechanism for this is that nests that share resources become more closely related due to migration and brood transfer. Finally, using a resource manipulation study, I found that resource-sharing networks can adapt in response to change in the availability of food. Together these results demonstrate how ant colonies can use polydomy to their advantage and the various factors that are important in determining the dynamics of these complex societies

The effect of social information on the collective choices of ant colonies

© 2016 The Author. In collective decision making, groups collate social information to inform their decisions. Indeed, societies can gather more information than individuals - so social information can be more reliable than private information. Colonies of Temnothorax albipennis can estimate the average quality of fluctuating nest sites when the sharing of social information through recruitment is rare. However, collective decisions in T. albipennis are often reached with the use of recruitment. We use a new experimental setup to test how colonies react to fluctuating nest sites when they use recruitment to reach a decision. When recruitment is used, colonies consistently choose nest sites that fluctuate between being "good" and "poor" over constantly "mediocre" alternatives. Moreover, they do so even if the fluctuating option is only "good" for 25% of the time. The ants' preference for fluctuating nest sites appears to be due to tandem running. Even if a nest site is only briefly "good," scouts that experience it when it is "good" are likely to perform tandem runs to it. However, a constantly "mediocre" nest site is unlikely to ever provoke tandem runs. Consequently, the fluctuating nest sites attracted more tandem runs, even when they were only "good" for a short time. This led to quorum attainment in fluctuating nest sites rather than in constant "mediocre" nest sites. The results of this experiment demonstrate how sharing of social information through recruitment can change the outcome of collective decisions

Lunisolar Perturbations of High-Eccentricity Orbits Such as the Magnetospheric Multiscale Mission

For highly eccentric orbits such as that of the Magnetospheric Multiscale (MMS)mission, with apogee radius now 29.34 Earth radii, the third-body effects of Sun andMoon are the major perturbations. One key consequence is an oscillation in MMSperigee altitude, on an approximately 6 year cycle. This variation has already requiredperigee-raise maneuvers to avoid an untimely reentry. There is also a long-termevolution in the orientation of the MMS orbit, with period roughly twice as long. Thiseffect may potentially be useful for MMS science studies, as it can bring the spacecraftinto new regions of the magnetosphere

Ant colony nest networks adapt to resource disruption

1. Animal social structure is shaped by environmental conditions, such as food availability. This is important as conditions are likely to change in the future and changes to social structure can have cascading ecological effects. Wood ants are a useful taxon for the study of the relationship between social structure and environmental conditions, as some populations form large nest networks and they are ecologically dominant in many northern hemisphere woodlands. Nest networks are formed when a colony inhabits more than one nest, known as polydomy. Polydomous colonies are composed of distinct sub-colonies that inhabit spatially distinct nests and that share resources with each other. 2. In this study, we performed a controlled experiment on ten polydomous wood ant (Formica lugubris) colonies to test how changing the resource environment affects the social structure of a polydomous colony. We took network maps of all colonies for five years before the experiment to assess how the networks changes under natural conditions. After this period, we prevented ants from accessing an important food source for a year in five colonies and left the other five colonies undisturbed. 4. We found that preventing access to an important food source causes polydomous wood ant colony networks to fragment into smaller components and begin foraging on previously unused food sources. These changes were not associated with a reduction in the growth of populations inhabiting individual nests (sub-colonies), foundation of new nests or survival, when compared with control colonies. 5. Colony splitting likely occurred as the availability of food in each nest changed causing sub-colonies to change their inter-nest connections. Consequently, our results demonstrate that polydomous colonies can adjust to environmental changes by altering their social network

The costs and benefits of decentralization and centralization of ant colonies

A challenge faced by individuals and groups of many species is determining how resources and activities should be spatially distributed: centralized or decentralized. This distribution problem is hard to understand due to the many costs and benefits of each strategy in different settings. Ant colonies are faced by this problem and demonstrate two solutions: 1) centralizing resources in a single nest (monodomy) and 2) decentralizing by spreading resources across many nests (polydomy). Despite the possibilities for using this system to study the centralization/decentralization problem, the trade-offs associated with using either polydomy or monodomy are poorly understood due to a lack of empirical data and cohesive theory. Here, we present a dynamic network model of a population of ant nests which is based on observations of a facultatively polydomous ant species (Formica lugubris). We use the model to test several key hypotheses for costs and benefits of polydomy and monodomy and show that decentralization is advantageous when resource acquisition costs are high, nest size is limited, resources are clustered, and there is a risk of nest destruction, but centralization prevails when resource availability fluctuates and nest size is limited. Our model explains the phylogenetic and ecological diversity of polydomous ants, demonstrates several trade-offs of decentralization and centralization, and provides testable predictions for empirical work on ants and in other systems

Poloxomer 188 Has a Deleterious Effect on Dystrophic Skeletal Muscle Function

Duchenne muscular dystrophy (DMD) is an X-linked, fatal muscle wasting disease for which there is currently no cure and limited palliative treatments. Poloxomer 188 (P188) is a tri-block copolymer that has been proposed as a potential treatment for cardiomyopathy in DMD patients. Despite the reported beneficial effects of P188 on dystrophic cardiac muscle function, the effects of P188 on dystrophic skeletal muscle function are relatively unknown. Mdx mice were injected intraperitoneally with 460 mg/kg or 30 mg/kg P188 dissolved in saline, or saline alone (control). The effect of single-dose and 2-week daily treatment was assessed using a muscle function test on the Tibialis Anterior (TA) muscle in situ in anaesthetised mice. The test comprises a warm up, measurement of the force-frequency relationship and a series of eccentric contractions with a 10% stretch that have previously been shown to cause a drop in maximum force in mdx mice. After 2 weeks of P188 treatment at either 30 or 460 mg/kg/day the drop in maximum force produced following eccentric contractions was significantly greater than that seen in saline treated control mice (P = 0.0001). Two week P188 treatment at either dose did not significantly change the force-frequency relationship or maximum isometric specific force produced by the TA muscle. In conclusion P188 treatment increases susceptibility to contraction-induced injury following eccentric contractions in dystrophic skeletal muscle and hence its suitability as a potential therapeutic for DMD should be reconsidered

Left out and locked down: impacts of COVID-19 for marginalised groups in Scotland

No abstract available