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1.  Worker Personality and Its Association with Spatially Structured Division of Labor 
PLoS ONE  2014;9(1):e79616.
Division of labor is a defining characteristic of social insects and fundamental to their ecological success. Many of the numerous tasks essential for the survival of the colony must be performed at a specific location. Consequently, spatial organization is an integral aspect of division of labor. The mechanisms organizing the spatial distribution of workers, separating inside and outside workers without central control, is an essential, but so far neglected aspect of division of labor. In this study, we investigate the behavioral mechanisms governing the spatial distribution of individual workers and its physiological underpinning in the ant Myrmica rubra. By investigating worker personalities we uncover position-associated behavioral syndromes. This context-independent and temporally stable set of correlated behaviors (positive association between movements and attraction towards light) could promote the basic separation between inside (brood tenders) and outside workers (foragers). These position-associated behavior syndromes are coupled with a high probability to perform tasks, located at the defined position, and a characteristic cuticular hydrocarbon profile. We discuss the potentially physiological causes for the observed behavioral syndromes and highlight how the study of animal personalities can provide new insights for the study of division of labor and self-organized processes in general.
PMCID: PMC3907378  PMID: 24497911
2.  Temnothorax pilagens sp. n. – a new slave-making species of the tribe Formicoxenini from North America (Hymenoptera, Formicidae) 
ZooKeys  2014;65-77.
A new species of the ant genus Temnothorax Forel, 1890 – Temnothorax pilagens sp. n. is described from eastern North America. T. pilagens sp. n. is an obligate slave-making ant with two known hosts: T. longispinosus (Roger, 1863) and T. ambiguus (Emery, 1895). A differential diagnosis against Temnothorax duloticus (Wesson, 1937), the other dulotic congener from the Nearctic, is presented and a biological characteristics of the new species is given.
PMCID: PMC3904070  PMID: 24478583
Temnothorax; Nearctic region; dulosis; slave-raiding behavior; morphometrics
3.  Inclusive fitness theory and eusociality 
Abbot, Patrick | Abe, Jun | Alcock, John | Alizon, Samuel | Alpedrinha, Joao A. C. | Andersson, Malte | Andre, Jean-Baptiste | van Baalen, Minus | Balloux, Francois | Balshine, Sigal | Barton, Nick | Beukeboom, Leo W. | Biernaskie, Jay M. | Bilde, Trine | Borgia, Gerald | Breed, Michael | Brown, Sam | Bshary, Redouan | Buckling, Angus | Burley, Nancy T. | Burton-Chellew, Max N. | Cant, Michael A. | Chapuisat, Michel | Charnov, Eric L. | Clutton-Brock, Tim | Cockburn, Andrew | Cole, Blaine J. | Colegrave, Nick | Cosmides, Leda | Couzin, Iain D. | Coyne, Jerry A. | Creel, Scott | Crespi, Bernard | Curry, Robert L. | Dall, Sasha R. X. | Day, Troy | Dickinson, Janis L. | Dugatkin, Lee Alan | El Mouden, Claire | Emlen, Stephen T. | Evans, Jay | Ferriere, Regis | Field, Jeremy | Foitzik, Susanne | Foster, Kevin | Foster, William A. | Fox, Charles W. | Gadau, Juergen | Gandon, Sylvain | Gardner, Andy | Gardner, Michael G. | Getty, Thomas | Goodisman, Michael A. D. | Grafen, Alan | Grosberg, Rick | Grozinger, Christina M. | Gouyon, Pierre-Henri | Gwynne, Darryl | Harvey, Paul H. | Hatchwell, Ben J. | Heinze, Jürgen | Helantera, Heikki | Helms, Ken R. | Hill, Kim | Jiricny, Natalie | Johnstone, Rufus A. | Kacelnik, Alex | Kiers, E. Toby | Kokko, Hanna | Komdeur, Jan | Korb, Judith | Kronauer, Daniel | Kümmerli, Rolf | Lehmann, Laurent | Linksvayer, Timothy A. | Lion, Sébastien | Lyon, Bruce | Marshall, James A. R. | McElreath, Richard | Michalakis, Yannis | Michod, Richard E. | Mock, Douglas | Monnin, Thibaud | Montgomerie, Robert | Moore, Allen J. | Mueller, Ulrich G. | Noë, Ronald | Okasha, Samir | Pamilo, Pekka | Parker, Geoff A. | Pedersen, Jes S. | Pen, Ido | Pfennig, David | Queller, David C. | Rankin, Daniel J. | Reece, Sarah E. | Reeve, Hudson K. | Reuter, Max | Roberts, Gilbert | Robson, Simon K. A. | Roze, Denis | Rousset, Francois | Rueppell, Olav | Sachs, Joel L. | Santorelli, Lorenzo | Schmid-Hempel, Paul | Schwarz, Michael P. | Scott-Phillips, Tom | Shellmann-Sherman, Janet | Sherman, Paul W. | Shuker, David M. | Smith, Jeff | Spagna, Joseph C. | Strassmann, Beverly | Suarez, Andrew V. | Sundström, Liselotte | Taborsky, Michael | Taylor, Peter | Thompson, Graham | Tooby, John | Tsutsui, Neil D. | Tsuji, Kazuki | Turillazzi, Stefano | Úbeda, Francisco | Vargo, Edward L. | Voelkl, Bernard | Wenseleers, Tom | West, Stuart A. | West-Eberhard, Mary Jane | Westneat, David F. | Wiernasz, Diane C. | Wild, Geoff | Wrangham, Richard | Young, Andrew J. | Zeh, David W. | Zeh, Jeanne A. | Zink, Andrew
Nature  2011;471(7339):10.1038/nature09831.
PMCID: PMC3836173  PMID: 21430721
4.  Raiders from the sky: slavemaker founding queens select for aggressive host colonies 
Biology Letters  2012;8(5):748-750.
Reciprocal selection pressures in host–parasite systems drive coevolutionary arms races that lead to advanced adaptations in both opponents. In the interactions between social parasites and their hosts, aggression is one of the major behavioural traits under selection. In a field manipulation, we aimed to disentangle the impact of slavemaking ants and nest density on aggression of Temnothorax longispinosus ants. An early slavemaker mating flight provided us with the unique opportunity to study the influence of host aggression and demography on founding decisions and success. We discovered that parasite queens avoided colony foundation in parasitized areas and were able to capture more brood from less aggressive host colonies. Host colony aggression remained consistent over the two-month experiment, but did not respond to our manipulation. However, as one-fifth of all host colonies were successfully invaded by parasite queens, slavemaker nest foundation acts as a strong selection event selecting for high aggression in host colonies.
PMCID: PMC3441009  PMID: 22809720
parasite; personality; dispersal; aggression; fitness
5.  Diverse societies are more productive: a lesson from ants 
The fitness consequences of animal personalities (also known as behavioural syndromes) have recently been studied in several solitary species. However, the adaptive significance of collective personalities in social insects and especially of behavioural variation among group members remains largely unexplored. Although intracolonial behavioural variation is an important component of division of labour, and as such a key feature for the success of societies, empirical links between behavioural variation and fitness are scarce. We investigated aggression, exploration and brood care behaviour in Temnothorax longispinosus ant colonies. We focused on two distinct aspects: intercolonial variability and its consistency across time and contexts, and intracolonial variability and its influence on productivity. Aggressiveness was consistent over four to five months with a new generation of workers emerging in between trial series. Other behaviours were not consistent over time. Exploration of novel environments responded to the sequence of assays: colonies were faster in discovering when workers previously encountered opponents in aggression experiments. Suites of correlated behaviours (e.g. aggression–exploration syndrome) present in the first series did not persist over time. Finally, colonies with more intracolonial behavioural variation in brood care and exploration of novel objects were more productive under standardized conditions than colonies with less variation.
PMCID: PMC3321703  PMID: 22279166
personality; behavioural syndromes; division of labour; fitness; social insects; aggression
6.  Characterizing the Collective Personality of Ant Societies: Aggressive Colonies Do Not Abandon Their Home 
PLoS ONE  2012;7(3):e33314.
Animal groups can show consistent behaviors or personalities just like solitary animals. We studied the collective behavior of Temnothorax nylanderi ant colonies, including consistency in behavior and correlations between different behavioral traits. We focused on four collective behaviors (aggression against intruders, nest relocation, removal of infected corpses and nest reconstruction) and also tested for links to the immune defense level of a colony and a fitness component (per-capita productivity). Behaviors leading to an increased exposure of ants to micro-parasites were expected to be positively associated with immune defense measures and indeed colonies that often relocated to other nest sites showed increased immune defense levels. Besides, colonies that responded with low aggression to intruders or failed to remove infected corpses, showed a higher likelihood to move to a new nest site. This resembles the trade-off between aggression and relocation often observed in solitary animals. Finally, one of the behaviors, nest reconstruction, was positively linked to per-capita productivity, whereas other colony-level behaviors, such as aggression against intruders, showed no association, albeit all behaviors were expected to be important for fitness under field conditions. In summary, our study shows that ant societies exhibit complex personalities that can be associated to the physiology and fitness of the colony. Some of these behaviors are linked in suites of correlated behaviors, similar to personalities of solitary animals.
PMCID: PMC3310061  PMID: 22457751
7.  Spatial structure and nest demography reveal the influence of competition, parasitism and habitat quality on slavemaking ants and their hosts 
BMC Ecology  2011;11:9.
Natural communities are structured by intra-guild competition, predation or parasitism and the abiotic environment. We studied the relative importance of these factors in two host-social parasite ecosystems in three ant communities in Europe (Bavaria) and North America (New York, West Virginia). We tested how these factors affect colony demography, life-history and the spatial pattern of colonies, using a large sample size of more than 1000 colonies. The strength of competition was measured by the distance to the nearest competitor. Distance to the closest social parasite colony was used as a measure of parasitism risk. Nest sites (i.e., sticks or acorns) are limited in these forest ecosystems and we therefore included nest site quality as an abiotic factor in the analysis. In contrast to previous studies based on local densities, we focus here on the positioning and spatial patterns and we use models to compare our predictions to random expectations.
Colony demography was universally affected by the size of the nest site with larger and more productive colonies residing in larger nest sites of higher quality. Distance to the nearest competitor negatively influenced host demography and brood production in the Bavarian community, pointing to an important role of competition, while social parasitism was less influential in this community. The New York community was characterized by the highest habitat variability, and productive colonies were clustered in sites of higher quality. Colonies were clumped on finer spatial scales, when we considered only the nearest neighbors, but more regularly distributed on coarser scales. The analysis of spatial positioning within plots often produced different results compared to those based on colony densities. For example, while host and slavemaker densities are often positively correlated, slavemakers do not nest closer to potential host colonies than expected by random.
The three communities are differently affected by biotic and abiotic factors. Some of the differences can be attributed to habitat differences and some to differences between the two slavemaking-host ecosystems. The strong effect of competition in the Bavarian community points to the scarcity of resources in this uniform habitat compared to the other more diverse sites. The decrease in colony aggregation with scale indicates fine-scale resource hotspots: colonies are locally aggregated in small groups. Our study demonstrates that species relationships vary across scales and spatial patterns can provide important insights into species interactions. These results could not have been obtained with analyses based on local densities alone. Previous studies focused on social parasitism and its effect on host colonies. The broader approach taken here, considering several possible factors affecting colony demography and not testing each one in isolation, shows that competition and environmental variability can have a similar strong impact on demography and life-history of hosts. We conclude that the effects of parasites or predators should be studied in parallel to other ecological influences.
PMCID: PMC3078833  PMID: 21443778
8.  Increased host aggression as an induced defense against slave-making ants 
Behavioral Ecology  2011;22(2):255-260.
Slave-making ants reduce the fitness of surrounding host colonies through regular raids, causing the loss of brood and frequently queen and worker death. Consequently, hosts developed defenses against slave raids such as specific recognition and aggression toward social parasites, and indeed, we show that host ants react more aggressively toward slavemakers than toward nonparasitic competitors. Permanent behavioral defenses can be costly, and if social parasite impact varies in time and space, inducible defenses, which are only expressed after slavemaker detection, can be adaptive. We demonstrate for the first time an induced defense against slave-making ants: Cues from the slavemaker Protomognathus americanus caused an unspecific but long-lasting behavioral response in Temnothorax host ants. A 5-min within-nest encounter with a dead slavemaker raised the aggression level in T. longispinosus host colonies. Contrarily, encounters with nonparasitic competitors did not elicit aggressive responses toward non-nestmates. Increased aggression can be adaptive if a slavemaker encounter reliably indicates a forthcoming attack and if aggression increases postraid survival. Host aggression was elevated over 3 days, showing the ability of host ants to remember parasite encounters. The response disappeared after 2 weeks, possibly because by then the benefits of increased aggression counterbalance potential costs associated with it.
PMCID: PMC3071747  PMID: 22476194
aggression; behavior; parasites; phenotypic plasticity; social insects
9.  Lifelong commitment to the wrong partner: hybridization in ants 
The extraordinary lifelong partner commitment in social insects is expected to increase choosiness in both sexes and therefore to be associated with particularly low hybridization frequencies. Yet, more and more studies reveal that in many ant taxa hybrids are surprisingly common, with up to half of all female sexuals receiving sperm from allospecific males in extreme cases. In a few ant species, hybridization has led to the evolution of reproductively isolated new lineages with a bizarre system of genetic caste differentiation: colonies produce hybrid workers and pure-lineage female sexuals. This requires that colonies either contain multiple queens or that queens mate multiple times. In most other cases, hybridization appears to be an evolutionary dead end and fertile hybrid queens are rarely found. In such cases, haplodiploid sex determination appears to decrease the costs of mating with an allospecific male. As long as hybrid workers are viable, a cross-mated queen can partially rescue its fitness by producing males from unfertilized eggs. Mating with an allospecific partner may thus be an option for queens when conspecific mates are not available. The morphological similarity of most ant males, perhaps resulting from the lack of sexual conflict, may similarly contribute to the commonness of hybridization.
PMCID: PMC2606732  PMID: 18508757
levels of selection; caste determination; sperm theft; mating biology; evolutionary arms races

Results 1-9 (9)