Personality in social insects： How does worker personality determine colony personality？

ASocial insect colonies and the workers comprising them, each exhibit consistent individual differences in behavior, also known as ＇personalities＇. Because the behavior of social insect colonies emerges from the actions of their workers, individual variation among workers＇ personality may be important in determining the variation we observe among colonies. The reproduc- tive unit of social insects, on which natural selection acts, is the colony, not individual workers. Therefore, it is important to un- derstand what mechanisms govern the observed variation among colonies. Here I propose three hypotheses that address how con- sistent individual differences in the behavior of workers may lead to consistent individual differences in the behavior of colonies： 1. Colonies differ consistently in their average of worker personality; 2. The distribution but not the average of worker personali- ties varies consistently among colonies; and 3. Colony personality does not emerge from its worker personality composition but from consistent external constraints. I review evidence supporting each of these hypotheses and suggest methods to further inves-tigate them. The study of how colony personality emerges from the personalities of the workers comprising them may shed light on the mechanisms underlying consistent individual differences in the behavior of other animals .

Persistent variation in spatial behavior affects the structure and function of interaction networks

The function of a network is affected by its structure. For example, the presence of highly interactive individuals, or hubs, influences the extent and rate of information spread across a network. In a network of interactions, the duration over which individual variation in interactions persists may affect how the network operates. Individuals may persist in their behavior over time and across situations, often referred to as personality. Colonies of social insects are an example of a biological system in which the structure of the coordinated networks of interacting workers may greatly influence information flow within the colony, and therefore its collective behavior. Here I investigate the effects of persistence in walking patterns on interaction networks us- ing computer simulations that are parameterized using observed behavior of harvester ants. I examine how the duration of persis- tence in spatial behavior influences network structure. Furthermore, I explore how spatial features of the environment affect the relationship between persistent behavior and network structure. I show that as persistence increases, the skewness of the weighted degree distribution of the interaction network increases. However, this relationship holds only when ants are confined in a space with boundaries, but not when physical barriers are absent. These findings suggest that the influence of animal personalities on network structure and function depends on the environment in which the animals reside [Current Zoology 61 （1）： 98-106, 2015].

Higher-Order Interactions： Understanding the knowledge capacity of social groups using simplicial sets

A predominant benefit of social living is the ability to share knowledge that cannot be gained through the information an individual accumulates based on its personal experience alone. Traditional computational models have portrayed sharing knowledge through interactions among members of social groups via dyadic networks. Such models aim at understanding the percolation of information among individuals and groups to identify potential limitations to successful knowledge transfer. How- ever, because many real-world interactions are not solely pairwise, i.e., several group members may obtain information from one another simultaneously, it is necessary to understand more than dyadic communication and learning processes to capture their full complexity. We detail a modeling framework based on the simplicial set, a concept from algebraic topology, which allows elegant encapsulation of multi-agent interactions. Such a model system allows us to analyze how individual information within groups accumulates as the group＇s collective set of knowledge, which may be different than the simple union of individually contained information. Furthermore, the simplicial modeling approach we propose allows us to investigate how information accumulates via sub-group interactions, offering insight into complex aspects of multi-way communication systems. The fundamental change in modeling strategy we offer here allows us to move from portraying knowledge as a ＂token＂, passed from signaler to receiver, to portraying knowledge as a set of accumulating building blocks from which novel ideas can emerge. We provide an explanation of relevant mathematical concepts in a way that promotes accessibility to a general audience [Current Zoology 61 （1）： 114--127, 2015].

Using multilayer network analysis to explore the temporal dynamics of collective behavior

Social organisms often show collective behaviors such as group foraging or movement.Collective behaviors can emerge from interactions between group members and may depend on the behavior of key individuals.When social interactions change over time,collective behaviors may change because these behaviors emerge from interactions among individuals.Despite the importance of,and growing interest in,the temporal dynamics of social interactions,it is not clear how to quantify changes in interactions over time or measure their stability.Furthermore,the temporal scale at which we should observe changes in social networks to detect biologically meaningful changes is not always apparent.Here we use multilayer network analysis to quantify temporal dynamics of social networks of the social spider Stegodyphus dumicola and determine how these dynamics relate to individual and group behaviors.We found that social interactions changed over time at a constant rate.Variation in both network structure and the identity of a keystone individual was not related to the mean or variance of the collective prey attack speed.Individuals that maintained a large and stable number of connections,despite changes in network structure,were the boldest individuals in the group.Therefore,social interactions and boldness are linked across time,but group collective behavior is not influenced by the stability of the social network.Our work demonstrates that dynamic social networks can be modeled in a multilayer framework.This approach may reveal biologically important temporal changes to social structure in other systems.

Colonies of ants allocate exploratory individuals to where they are ecologically needed

Individual differences in behavior have large consequences for the way in which ecology impacts fitness.Individuals differ in how they explore their environment and how exploratory behavior benefits them.In group-living animals,behavioral heterogeneity can be beneficial because different individuals perform different tasks.For example,exploratory individuals may discover new food sources and recruit group members to exploit the food,while less exploratory individuals forgo the risks of exploration.Here we ask how individual variation in exploratory behavior affects the ability of Argentine ant Linepithema humile colonies to(1)locate novel food sources,(2)exploit known food resources,and(3)respond to disruptions while foraging.To address these questions,we conducted field experiments on L.humile foraging trails in which we manipulated food availability near and at the foraging trails and disrupted the foraging trails.We sampled individuals based on their response to the perturbations in the field and tested their exploratory behavior in the lab.We found that exploratory individuals benefit the colony by locating novel foods and increasing resource exploitation,but they do not play an important role in the recovery of a foraging trail after disruption.Thus,the benefits of behavioral heterogeneity to the group,specifically in exploratory behavior,differ across ecological contexts.

Nutritional needs and mortality risk combine to shape foraging decisions in ants

When foraging,internal needs for particular nutrients might affect food choice,and external constraints,such as predation risk,might impact trade-offs between foraging and risk avoidance.Examining both internal and external constraints simultaneously can provide important insights into how animals make decisions.We examined how internal nutritional needs and external cues of mortality risk jointly impact the foraging behavior of ants.Ant colonies require carbohydrates to support workers energetically and proteins to raise brood.Furthermore,colonies adjust their foraging activity in response to the environment,such as food availability and the presence of predators or heterospecifics.Here we exam-ine the foraging decisions of groups of Argentine ants Linepithema humile,which differ in their nutritional needs in high-risk environments.We starved groups of ants for either proteins or carbohydrates and determined the foraging choices that ants made when cues of heterospecifics were present.We found that ants preferentially forage for carbohydrates in high-risk conditions.Furthermore,starvation for carbohydrates increased the ants'preference for carbohydrates,even when cues of heterospecifics were present at both carbohydrates and protein resources.Starvation for protein also resulted in preferential foraging for carbohydrates,but it increased visitation to a protein food source in high-risk envi-ronments compared to when ants were starved for carbohydrates or for both resources.Examining the effect of both nutrition and mortality risk on foraging simultaneously provides insights about state-dependent risk-taking behavior that may have important implications for predicting theinvasionofspecies intonovelhabitats.