Latitudinal variation in behaviors linked to risk tolerance is driven by nest-site competition and spatial distribution in the ant Temnothorax rugatulus

Behavioral syndromes in paper wasps: Links between social and non-social personality in Polistes fuscatus

Although much work has focused on non-social personality traits such as activity, exploration, and neophobia, there is a growing appreciation that social personality traits play an important role in group dynamics, disease transmission, and fitness and that social personality traits may be linked to non-social personality traits. These relationships are important because behavioral syndromes, defined here as correlated behavioral phenotypes, can constrain evolutionary responses. However, the strength and direction of relationships between social and non-social personality traits remain unclear. In this project, we examine social and non-social personality traits, and the relationships between them, in the paper wasp Polistes fuscatus. With a novel assay, we identify 5 personality traits, 2 non-social (exploration and activity), and 3 social (aggression, affiliation, and antennation) personality traits. We also find that social and non-social personality traits are phenotypically linked. We find a positive correlation between aggression and activity and a negative correlation between affiliation and activity. We also find a positive correlation between exploration and activity. Our work is an important step in understanding how phenotypic linkage between social and non-social behaviors may influence behavioral evolution. As a burgeoning model system for the study of genetic and neurobiological mechanisms of social behavior, Polistes fuscatus has the potential to add to this work by exploring the causes and consequences of individual behavioral variation.

Foraging valor linked with aggression: selection against completely abandoning aggression in the high-elevation ant Tetramorium alpestre?

Aggression has multiple benefits and is often coupled with other behaviors ("behavioral syndromes"). The level of aggressiveness is influenced by an adaptive benefit-cost ratio suggesting that benefits should outweigh the costs of aggression. Here, we assess if several behaviors are coupled in two behaviorally different populations (aggressive, peaceful) of the high-elevation ant Tetramorium alpestre. For three weeks, we collected colony fragments and analyzed boldness, exploring, foraging, and risk-taking behaviors. We hypothesized that the aggressive population is bolder, more explorative and risk-prone, and forages more food than the peaceful population. To test whether (a) the combination of experiments and parameters used yields a good setup, (b) populations differ behaviorally, and (c) populations display behavioral syndromes, we assessed (a) the frequency of repeatable behaviors of each experiment, (b) the behavioral means among populations, and (c) the behavioral repeatability, respectively. We found that (a) boldness and exploring were most repeatable and represent a good experimental setup, (b) the aggressive population was bolder and more explorative and risk-prone than the peaceful population, (c) boldness and exploring behaviors were highly repeatable in both populations, thus corroborating our hypothesis. The results suggest that boldness, exploring, and risk-taking but not foraging are presumably coupled with aggression and indicate the presence of behavioral syndromes in this ant. Under specific ecological conditions, aggression may be coupled with other behaviors and important for finding food. Aggression is probably adaptive in T. alpestre, possibly indicating that selection favors aggression at least partially, which may counteract the complete loss of intraspecific aggression.

Geographical variation in nest defense among cinereous tit populations in China

Behavioral divergence among populations is common across taxonomic groups, still we know very little about anti-predator behaviors. Animal exposure to predation risk is variable in different ecological contexts. In addition, reproduction value of animals in different geographical regions usually varies. In this study, we tested whether cinereous tits Parus cinereus in different populations exhibited nest defense behaviors similar to those of nest or adult predators and whether their nest defense behaviors showed geographical variation. By using field dummy experiments, we observed tits’ nest defense behavior in nest predator common chipmunk Tamias sibiricus and red squirrel Sciurus vulgaris, adult predator Eurasian sparrowhawk Accipiter nisus and nonthreatening species Oriental turtle dove Streptopelia orientalis in the ZJ (44° N), DLS (18° N) and DZ (31° N) populations, respectively. The response scores varied significantly across the four dummies in ZJ-tits and DLS-tits but did not in DZ-tits. When facing the chipmunk, ZJ-tits showed the highest response score, and DZ-tits showed the lowest response score. When facing the squirrel, ZJ-tits showed a higher response score than tits in the other two populations. However, tits among the three populations responded similarly to a sparrowhawk or dove with slight response behaviors. In addition, response scores to nest predators were positively correlated with brood size across the three populations, but no trend was found for sparrowhawks or doves. Our results indicated that the nest defense behaviors of cinereous tits have evolved in response to large-scale geographical variation in ecological contexts and reproduction value.

Distributed Adaptive Search in T Cells: Lessons From Ants

There are striking similarities between the strategies ant colonies use to forage for food and immune systems use to search for pathogens. Searchers (ants and cells) use the appropriate combination of random and directed motion, direct and indirect agent-agent interactions, and traversal of physical structures to solve search problems in a variety of environments. An effective immune response requires immune cells to search efficiently and effectively for diverse types of pathogens in different tissues and organs, just as different species of ants have evolved diverse search strategies to forage effectively for a variety of resources in a variety of habitats. Successful T cell search is required to initiate the adaptive immune response in lymph nodes and to eradicate pathogens at sites of infection in peripheral tissue. Ant search strategies suggest novel predictions about T cell search. In both systems, the distribution of targets in time and space determines the most effective search strategy. We hypothesize that the ability of searchers to sense and adapt to dynamic targets and environmental conditions enhances search effectiveness through adjustments to movement and communication patterns. We also suggest that random motion is a more important component of search strategies than is generally recognized. The behavior we observe in ants reveals general design principles and constraints that govern distributed adaptive search in a wide variety of complex systems, particularly the immune system.

The Ecology of Collective Behavior in Ants

Nest choice in Temnothorax spp.; task allocation and the regulation of activity in Pheidole dentata, Pogonomyrmex barbatus, and Atta spp.; and trail networks in Monomorium pharaonis and Cephalotes goniodontus all provide examples of correspondences between the dynamics of the environment and the dynamics of collective behavior. Some important aspects of the dynamics of the environment include stability, the threat of rupture or disturbance, the ratio of inflow and outflow of resources or energy, and the distribution of resources. These correspond to the dynamics of collective behavior, including the extent of amplification, how feedback instigates and inhibits activity, and the extent to which the interactions that provide the information to regulate behavior are local or spatially centralized.

Colony personality and plant health in the Azteca-Cecropia mutualism

For interspecific mutualisms, the behavior of one partner can influence the fitness of the other, especially in the case of symbiotic mutualisms where partners live in close physical association for much of their lives. Behavioral effects on fitness may be particularly important if either species in these long-term relationships displays personality. We conducted a field study on collective personality in Azteca constructor colonies that live in Cecropia trees, one of the most successful and prominent mutualisms of the neotropics. These pioneer plants provide hollow internodes for nesting and nutrient-rich food bodies; in return, the ants provide protection from herbivores and encroaching vines. We tested the consistency and correlation of 5 colony-level behavioral traits, censused colonies, and measured the amount of leaf damage for each plant. Four of five traits were both consistent within colonies and correlated among colonies. This reveals a behavioral syndrome along a docile-aggressive axis, with higher-scoring colonies showing greater activity, aggression, and responsiveness. Scores varied substantially between colonies and were independent of colony size and age. Host plants of more active, aggressive colonies had less leaf damage, suggesting a link between a colony’s personality and effective defense of its host, though the directionality of this link remains uncertain. Our field study shows that colony personality is an ecologically relevant phenomenon and sheds light on the importance of behavioral differences within mutualism dynamics.

Who needs 'lazy' workers? Inactive workers act as a 'reserve' labor force replacing active workers, but inactive workers are not replaced when they are removed

Social insect colonies are highly successful, self-organized complex systems. Surprisingly however, most social insect colonies contain large numbers of highly inactive workers. Although this may seem inefficient, it may be that inactive workers actually contribute to colony function. Indeed, the most commonly proposed explanation for inactive workers is that they form a 'reserve' labor force that becomes active when needed, thus helping mitigate the effects of colony workload fluctuations or worker loss. Thus, it may be that inactive workers facilitate colony flexibility and resilience. However, this idea has not been empirically confirmed. Here we test whether colonies of Temnothorax rugatulus ants replace highly active (spending large proportions of time on specific tasks) or highly inactive (spending large proportions of time completely immobile) workers when they are experimentally removed. We show that colonies maintained pre-removal activity levels even after active workers were removed, and that previously inactive workers became active subsequent to the removal of active workers. Conversely, when inactive workers were removed, inactivity levels decreased and remained lower post-removal. Thus, colonies seem to have mechanisms for maintaining a certain number of active workers, but not a set number of inactive workers. The rapid replacement (within 1 week) of active workers suggests that the tasks they perform, mainly foraging and brood care, are necessary for colony function on short timescales. Conversely, the lack of replacement of inactive workers even 2 weeks after their removal suggests that any potential functions they have, including being a 'reserve', are less important, or auxiliary, and do not need immediate recovery. Thus, inactive workers act as a reserve labor force and may still play a role as food stores for the colony, but a role in facilitating colony-wide communication is unlikely. Our results are consistent with the often cited, but never yet empirically supported hypothesis that inactive workers act as a pool of 'reserve' labor that may allow colonies to quickly take advantage of novel resources and to mitigate worker loss.

The behavioral ecology of variation in social insects

Understanding the ecological relevance of variation within and between colonies has been an important and recurring theme in social insect research. Recent research addresses the genomic and physiological factors and fitness effects associated with behavioral variation, within and among colonies, in regulation of activity, cognitive abilities, and aggression. Behavioral variation among colonies has consequences for survival and reproductive success that are the basis for evolutionary change.