1
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Kreider JJ, Kramer BH, Komdeur J, Pen I. The evolution of ageing in cooperative breeders. Evol Lett 2022; 6:450-459. [PMID: 36579168 PMCID: PMC9783459 DOI: 10.1002/evl3.307] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 10/24/2022] [Accepted: 11/06/2022] [Indexed: 12/03/2022] Open
Abstract
Cooperatively breeding animals live longer than their solitary counterparts. This has been suggested for birds, mole rats, and social insects. A common explanation for these long lifespans is that cooperative breeding evolves more readily in long-lived species because lower mortality reduces the rate of territory turnover and thus leads to a limitation of breeding territories. Here, we reverse this argument and show that-rather than being a cause for its evolution-long lifespans are an evolutionary consequence of cooperative breeding. In evolutionary individual-based simulations, we show that natural selection favors a delayed onset of senescence in cooperative breeders, relative to solitary breeders, because cooperative breeders have a delayed age of first reproduction as helpers wait in a reproductive queue to obtain breeder status. Especially long lifespans evolve in cooperative breeders in which queue positions depend on the helpers' age rank among the helpers within the breeding territory. Furthermore, we show that lower genetic relatedness among group members leads to the evolution of longer lifespans. This is because selection against higher mortality is weaker when mortality reduces competition for breeding between relatives. Our results link the evolutionary theory of ageing with kin selection theory, demonstrating that the evolution of ageing in cooperative breeders is driven by the timing of reproduction and kin structure within breeding territories.
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Affiliation(s)
- Jan J. Kreider
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands,Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Boris H. Kramer
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Jan Komdeur
- Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Ido Pen
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
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2
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Jeanne RL, Loope KJ, Bouwma AM, Nordheim EV, Smith ML. Five decades of misunderstanding in the social Hymenoptera: a review and meta-analysis of Michener's paradox. Biol Rev Camb Philos Soc 2022; 97:1559-1611. [PMID: 35338566 PMCID: PMC9546470 DOI: 10.1111/brv.12854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/15/2022] [Accepted: 03/17/2022] [Indexed: 12/22/2022]
Abstract
In a much-cited 1964 paper entitled "Reproductive efficiency in relation to colony size in hymenopterous societies," Charles Michener investigated the correlation between a colony's size and its reproductive efficiency - the ability of its adult females to produce reproductives, measured as per-capita output. Based on his analysis of published data from destructively sampled colonies in 18 species, he reported that in most of these species efficiency decreased with increasing colony size. His conclusion that efficiency is higher in smaller groups has since gained widespread acceptance. But it created a seeming paradox: how can natural selection maintain social behaviour when a female apparently enjoys her highest per-capita output by working alone? Here we treat Michener's pattern as a hypothesis and perform the first large-scale test of its prediction across the eusocial Hymenoptera. Because data on actual output of reproductives were not available for most species, Michener used various proxies, such as nest size, numbers of brood, or amounts of stored food. We show that for each of Michener's data sets the reported decline in per-capita productivity can be explained by factors other than decreasing efficiency, calling into question his conclusion that declining efficiency is the cause of the pattern. The most prominent cause of bias is the failure of the proxy to capture all forms of output in which the colony invests during the course of its ontogeny. Other biasing factors include seasonal effects and a variety of methodological flaws in the data sets he used. We then summarize the results of 215 data sets drawn from post-1964 studies of 80 species in 33 genera that better control for these factors. Of these, 163 data sets are included in two meta-analyses that statistically synthesize the available data on the relationship between colony size and efficiency, accounting for variable sample sizes and non-independence among the data sets. The overall effect, and those for most taxonomic subgroups, indicates no loss of efficiency with increasing colony size. Two exceptional taxa, the halictid bees and independent-founding paper wasps, show negative trends consistent with the Michener hypothesis in some species. We conclude that in most species, particularly those with large colony sizes, the hypothesis of decreasing efficiency with increasing colony size is not supported. Finally, we explore potential mechanisms through which the level of efficiency can decrease, be maintained, or even increase, as colonies increase in size.
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Affiliation(s)
- Robert L Jeanne
- Department of Entomology, University of Wisconsin, 1630 Linden Drive, Madison, WI, 53706, U.S.A
| | - Kevin J Loope
- Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University (Virginia Tech), Cheatham Hall, 310 W. Campus Drive, Blacksburg, VA, 24060, U.S.A
| | - Andrew M Bouwma
- Department of Integrative Biology, Oregon State University, Cordley Hall, 3029, 2701 SW Campus Way, Corvallis, OR, 97331, U.S.A
| | - Erik V Nordheim
- Department of Statistics, University of Wisconsin, 1300 University Avenue, Madison, WI, 53706, U.S.A
| | - Michael L Smith
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, U.S.A
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3
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Honorio R, Jacquier L, Doums C, Molet M. Disentangling the roles of social and individual effects on cadmium tolerance in the ant Temnothorax nylanderi. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Urbanization brings new pressures for individuals. Among them, trace elements, such as cadmium, are important stressors. A recent study highlights a weaker negative effect of cadmium on city colonies relative to their forest counterparts in the ant Temnothorax nylanderi. Here, we aim to test whether the better tolerance of city colonies in this species results from a better ability of workers to rear larvae despite stressful conditions and/or a better ability of larvae to develop properly despite stressful conditions. We performed a cross-fostering experiment of workers and larvae from city and forest colonies, in common garden conditions in the laboratory. Colonies were fed using cadmium-enriched or cadmium-free food for 2 months, and we measured four life-history traits. As expected, cadmium had a negative impact on all traits. Unexpectedly, we did not observe a better tolerance of city colonies to cadmium, contrary to our previous study, which prevented us from disentangling the respective contributions of workers and larvae to cadmium tolerance. Interestingly, forest colonies seemed to be of better quality in our laboratory conditions. Finally, colony size increased adult survival, but only in the absence of cadmium, suggesting that social buffering could collapse with strong external disturbances.
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Affiliation(s)
- Romain Honorio
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
| | - Lauren Jacquier
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
| | - Claudie Doums
- Institut de Systématique Évolution Biodiversité, ISYEB, F-75005 Paris, Sorbonne Université, MNHN, CNRS, EPHE-PSL, Université des Antilles, France
- EPHE, PSL University, F-75014 Paris, France
| | - Mathieu Molet
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
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4
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Sanmartín-Villar I, Jeanson R. Early social context does not influence behavioral variation at adulthood in ants. Curr Zool 2021; 68:335-344. [PMID: 35592349 PMCID: PMC9113369 DOI: 10.1093/cz/zoab063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 07/27/2021] [Indexed: 01/15/2023] Open
Abstract
Early experience can prepare offspring to adapt their behaviors to the environment they are likely to encounter later in life. In several species of ants, colonies show ontogenic changes in the brood-to-worker ratio that are known to have an impact on worker morphology. However, little information is available on the influence of fluctuations in the early social context on the expression of behavior in adulthood. Using the ant Lasius niger, we tested whether the brood-to-worker ratio during larval stages influenced the level of behavioral variability at adult stages. We raised batches of 20 or 180 larvae in the presence of 60 workers until adulthood. We then quantified the activity level and wall-following tendency of callow workers on 10 successive trials to test the prediction that larvae reared under a high brood-to-worker ratio should show greater behavioral variations. We found that manipulation of the brood-to-worker ratio influenced the duration of development and the size of individuals at emergence. We detected no influence of early social context on the level of between- or within-individual variation measured for individual activity level or on wall-following behavior. Our study suggests that behavioral traits may be more canalized than morphological traits.
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Affiliation(s)
- Iago Sanmartín-Villar
- Centre de Recherches Sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
- Universidade de Vigo, ECOEVO Lab, Escola de Enxeñaría Forestal, Campus A Xunqueira, Pontevedra, Spain
| | - Raphaël Jeanson
- Centre de Recherches Sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
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5
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De Gasperin O, Blacher P, Chapuisat M. Social insect colonies are more likely to accept unrelated queens when they come with workers. Behav Ecol 2021. [DOI: 10.1093/beheco/arab047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Abstract
Relatedness underlies the evolution of reproductive altruism, yet eusocial insect colonies occasionally accept unrelated reproductive queens. Why would workers living in colonies with related queens accept unrelated ones, when they do not gain indirect fitness through their reproduction? To understand this seemingly paradox, we investigated whether acceptance of unrelated queens by workers is an incidental phenomenon resulting from failure to recognize non-nestmate queens, or whether it is adaptively favored in contexts where cooperation is preferable to rejection. Our study system is the socially polymorphic Alpine silver ant, Formica selysi. Within populations, some colonies have a single queen, and others have multiple, sometimes unrelated, breeding queens. Social organization is determined by a supergene with two haplotypes. In a first experiment, we investigated whether the number of reproductive queens living in colonies affects the ability of workers at rejecting alien queens, as multiple matrilines within colonies could increase colony odor diversity and reduce workers’ recognition abilities. As workers rejected all alien queens, independently of the number of queens heading their colony, we then investigated whether their acceptance is flexible and favored in specific conditions. We found that workers frequently accepted alien queens when these queens came with a workforce. Our results show that workers flexibly adjust their acceptance of alien queens according to the situation. We discuss how this conditional acceptance of unrelated queens may be adaptive by providing benefits through increased colony size and/or genetic diversity, and by avoiding rejection costs linked to fighting.
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Affiliation(s)
- Ornela De Gasperin
- Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland
| | - Pierre Blacher
- Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland
| | - Michel Chapuisat
- Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland
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6
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Scharf I, Stoldt M, Libbrecht R, Höpfner AL, Jongepier E, Kever M, Foitzik S. Social isolation causes downregulation of immune and stress response genes and behavioural changes in a social insect. Mol Ecol 2021; 30:2378-2389. [PMID: 33772940 DOI: 10.1111/mec.15902] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 03/16/2021] [Accepted: 03/22/2021] [Indexed: 12/27/2022]
Abstract
Humans and other social mammals experience isolation from their group as stressful, triggering behavioural and physiological anomalies that reduce fitness. While social isolation has been intensely studied in social mammals, it is less clear how social insects, which evolved sociality independently, respond to isolation. Here we examined whether the typical mammalian responses to social isolation, e.g., an impaired ability to interact socially and immune suppression are also found in social insects. We studied the consequences of social isolation on behaviour and brain gene expression in the ant Temnothorax nylanderi. Following isolation, workers interacted moderately less with adult nestmates, increased the duration of brood contact, and reduced the time spent self-grooming, an important sanitary behaviour. Our brain transcriptome analysis revealed that only a few behaviour-related genes had altered their expression with isolation time. Rather, many genes linked to immune system functioning and stress response had been downregulated. This probably sensitizes isolated individuals to various stressors, in particular because isolated workers exhibit reduced sanitary behaviour. We provide evidence of the diverse consequences of social isolation in social insects, some of which resemble those found in social mammals, suggesting a general link between social well-being, stress tolerance, and immune competence in social animals.
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Affiliation(s)
- Inon Scharf
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Marah Stoldt
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Romain Libbrecht
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Anna Lena Höpfner
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Evelien Jongepier
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Marion Kever
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Susanne Foitzik
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
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7
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Kennedy P, Sumner S, Botha P, Welton NJ, Higginson AD, Radford AN. Diminishing returns drive altruists to help extended family. Nat Ecol Evol 2021; 5:468-479. [PMID: 33589803 PMCID: PMC7610556 DOI: 10.1038/s41559-020-01382-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 12/10/2020] [Indexed: 11/09/2022]
Abstract
Altruism between close relatives can be easily explained. However, paradoxes arise when organisms divert altruism towards more distantly related recipients. In some social insects, workers drift extensively between colonies and help raise less related foreign brood, seemingly reducing inclusive fitness. Since being highlighted by W. D. Hamilton, three hypotheses (bet hedging, indirect reciprocity and diminishing returns to cooperation) have been proposed for this surprising behaviour. Here, using inclusive fitness theory, we show that bet hedging and indirect reciprocity could only drive cooperative drifting under improbable conditions. However, diminishing returns to cooperation create a simple context in which sharing workers is adaptive. Using a longitudinal dataset comprising over a quarter of a million nest cell observations, we quantify cooperative payoffs in the Neotropical wasp Polistes canadensis, for which drifting occurs at high levels. As the worker-to-brood ratio rises in a worker's home colony, the predicted marginal benefit of a worker for expected colony productivity diminishes. Helping related colonies can allow effort to be focused on related brood that are more in need of care. Finally, we use simulations to show that cooperative drifting evolves under diminishing returns when dispersal is local, allowing altruists to focus their efforts on related recipients. Our results indicate the power of nonlinear fitness effects to shape social organization, and suggest that models of eusocial evolution should be extended to include neglected social interactions within colony networks.
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Affiliation(s)
- P. Kennedy
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK,Correspondence:
| | - S. Sumner
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - P. Botha
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - N. J. Welton
- Population Health Sciences, Bristol Medical School, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK
| | - A. D. Higginson
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, EX4 4QG, UK
| | - A. N. Radford
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
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8
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Mitrus S. No effect of lack of wood for acorn ant colonies development. THE EUROPEAN ZOOLOGICAL JOURNAL 2021. [DOI: 10.1080/24750263.2020.1856950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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9
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Liu 劉彥廷 M, Chan 詹仕凡 SF, Rubenstein DR, Sun 孫烜駿 SJ, Chen 陳伯飛 BF, Shen 沈聖峰 SF. Ecological Transitions in Grouping Benefits Explain the Paradox of Environmental Quality and Sociality. Am Nat 2020; 195:818-832. [PMID: 32364780 DOI: 10.1086/708185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Both benign and harsh environments promote the evolution of sociality. This paradox-societies occur in environments of such contrasting quality-may be explained by the different types of benefits that individuals receive from grouping: resource defense benefits that derive from group-defended critical resources versus collective action benefits that result from social cooperation among group members. Here, we investigate cooperative behavior in the burying beetle Nicrophorus nepalensis along an elevational gradient where environmental quality (climate and competition) varies with altitude. We show that climate (temperature) and competition (both intra- and interspecific) independently and synergistically influence sociality via different grouping benefits that vary along the gradient. At low elevations where interspecific competition for resources is intense, groups gain from the collective action benefit of increased interspecific competitive ability. In contrast, pairs have higher fitness at intermediate elevations where intraspecific competition for resources is greatest because resource defense is the key grouping benefit. However, groups and pairs have similar fitness at high elevations, suggesting that there is no grouping benefit in such physiologically challenging environments. Our results demonstrate that sociality is favored for different reasons under a range of environmental conditions, perhaps explaining why animal societies occur in environments of such contrasting quality.
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10
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Field J, Toyoizumi H. The evolution of eusociality: no risk-return tradeoff but the ecology matters. Ecol Lett 2019; 23:518-526. [PMID: 31884729 PMCID: PMC7027560 DOI: 10.1111/ele.13452] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/02/2019] [Indexed: 11/27/2022]
Abstract
The origin of eusociality in the Hymenoptera is a question of major interest. Theory has tended to focus on genetic relatedness, but ecology can be just as important a determinant of whether eusociality evolves. Using the model of Fu et al. (2015), we show how ecological assumptions critically affect the conclusions drawn. Fu et al. inferred that eusociality rarely evolves because it faces a fundamental ‘risk‐return tradeoff’. The intuitive logic was that worker production represents an opportunity cost because it delays realising a reproductive payoff. However, making empirically justified assumptions that (1) workers take over egg‐laying following queen death and (2) productivity increases gradually with each additional worker, we find that the risk‐return tradeoff disappears. We then survey Hymenoptera with more specialised morphological castes, and show how the interaction between two common features of eusociality – saturating birth rates and group size‐dependent helping decisions – can determine whether eusociality outperforms other strategies.
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Affiliation(s)
- Jeremy Field
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall, TR10 9EZ, UK
| | - Hiroshi Toyoizumi
- Graduate School of Accounting and Department of Applied Mathematics, Waseda University, Nishi-waseda 1-6-1, Shinjuku, Tokyo, 169-8050, Japan
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11
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Doering GN, Sheehy KA, Barnett JB, Pruitt JN. Colony size and initial conditions combine to shape colony reunification dynamics. Behav Processes 2019; 170:103994. [PMID: 31689459 DOI: 10.1016/j.beproc.2019.103994] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/24/2019] [Accepted: 10/28/2019] [Indexed: 11/20/2022]
Abstract
Group cohesion and collective decision-making are important for many social animals, like social insects, whose societies depend on the coordinated action of individuals to complete collective tasks. A useful model for understanding collective, consensus-driven decision-making is the fluid nest selection dynamics of ant colonies. Certain ant species oscillate between occupying multiple nests simultaneously (polydomy) and reuniting at a single location (monodomy), but little is known about how colonies achieve a consensus around these dynamics. To investigate the factors underpinning the splitting-reunification dynamics of ants, we manipulated the availability and quality of nest sites for the ant Temnothorax rugatulus and measured the likelihood and speed of reunification from contrasting starting conditions. We found that pursuing reunification was more likely for smaller colonies, that rates of initial splitting were lower when colonies could coordinate their activity from a central hub, and that diluting colonies among additional sites did not impair reaching consensus on a single nest. We further found mixed support for a specific threshold of social density that prevents reunification (i.e., prolonged polydomy) and no evidence that nest quality influences reunification behavior. Together our data reveal that consensus driven decisions can be influenced by both external and intrinsic group-level factors and are in no way simple stereotyped processes.
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Affiliation(s)
- Grant Navid Doering
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.
| | - Kirsten A Sheehy
- Department of Ecology, Evolution & Marine Biology, University of California - Santa Barbara, Santa Barbara, CA, 93106, USA
| | - James B Barnett
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - Jonathan N Pruitt
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
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12
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Burns DDR, Pitchford JW, Parr CL, Franks DW, Robinson EJH. The costs and benefits of decentralization and centralization of ant colonies. Behav Ecol 2019; 30:1700-1706. [PMID: 31723318 PMCID: PMC6838651 DOI: 10.1093/beheco/arz138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 05/31/2019] [Accepted: 07/22/2019] [Indexed: 11/16/2022] Open
Abstract
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.
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Affiliation(s)
- Dominic D R Burns
- Department of Biology, Wentworth Way, University of York, York, UK
- York Cross-disciplinary Centre for Systems Analysis, University of York, York, UK
| | - Jon W Pitchford
- Department of Biology, Wentworth Way, University of York, York, UK
- Department of Mathematics, University of York, York, UK
| | - Catherine L Parr
- Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Jane Herdman Building, Liverpool, UK
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Wits, South Africa
- Department of Zoology and Entomology, University of Pretoria, Hatfield, Pretoria
| | - Daniel W Franks
- Department of Biology, Wentworth Way, University of York, York, UK
- York Cross-disciplinary Centre for Systems Analysis, University of York, York, UK
- Department of Computer Science, Deramore Lane, University of York, York, UK
| | - Elva J H Robinson
- Department of Biology, Wentworth Way, University of York, York, UK
- York Cross-disciplinary Centre for Systems Analysis, University of York, York, UK
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13
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Jeanson R. Within-individual behavioural variability and division of labour in social insects. ACTA ACUST UNITED AC 2019; 222:222/10/jeb190868. [PMID: 31127006 DOI: 10.1242/jeb.190868] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Division of labour, whereby individuals divide the workload in a group, is a recurrent property of social living. The current conceptual framework for division of labour in social insects is provided by the response-threshold model. This model posits that the differences between individuals (i.e. between-individual variability) in responsiveness to task-associated stimuli is a key feature for task specialisation. The consistency of individual behaviours (i.e. within-individual variability) in task performance represents an additional but little-considered component driving robust patterns of division of labour. On the one hand, the presence of workers with a high level of within-individual variability presumably allows colonies to rapidly adapt to external fluctuations. On the other hand, a reduced degree of within-individual variability promotes a stricter specialisation in task performance, thereby limiting the costs of task switching. The ideal balance between flexibility and canalisation probably varies depending on the developmental stage of the colony to satisfy its changing needs. Here, I introduce the main sources of within-individual variability in behaviours in social insects and I review neural correlates accompanying the changes in behavioural flexibility. I propose the hypothesis that the positive scaling between group size and the intensity of task specialisation, a relationship consistently reported both within and between taxa, may rely on reduced within-individual variability via self-organised processes linked to the quality of brood care. Overall, I emphasise the need for a more comprehensive characterisation of the response dynamics of individuals to better understand the mechanisms shaping division of labour in social insects.
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Affiliation(s)
- Raphaël Jeanson
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 31062 Toulouse Cedex 9, France
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14
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Varoudis T, Swenson AG, Kirkton SD, Waters JS. Exploring nest structures of acorn dwelling ants with X-ray microtomography and surface-based three-dimensional visibility graph analysis. Philos Trans R Soc Lond B Biol Sci 2018; 373:20170237. [PMID: 29967301 PMCID: PMC6030587 DOI: 10.1098/rstb.2017.0237] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/04/2018] [Indexed: 12/16/2022] Open
Abstract
The physical spaces within which organisms live affect their biology and in many cases can be considered part of their extended phenotype. The nests of social insect societies have a fundamental impact on their ability to function as complex superorganisms. Ants in many species excavate elaborate subterranean nests, but others inhabit relatively small pre-formed cavities within rock crevices and hollow seeds. Temnothorax ants, which often nest within acorns, have become a model system for studying collective decision making. While these ants have demonstrated remarkable degrees of rationality and consistent precision with regard to their nest choices, never before has the fine scale internal architecture and spatial organization of their nests been investigated. We used X-ray microtomography to record high-resolution three-dimensional (3D) scans of Temnothorax colonies within their acorns. These data were then quantified using image segmentation and surface-based 3D visibility graph analysis, a new computational methodology for analysing spatial structures. The visibility graph analysis method integrates knowledge from the field of architecture with the empirical study of animal-built structures, thus providing the first methodological cross-disciplinary synergy of these two research areas. We found a surprisingly high surface area and degree of spatial heterogeneity within the acorn nests. Specific regions, such as those associated with the locations of queens and brood, were significantly more conducive to connectivity than others. From an architect's point of view, spatial analysis research has never focused on all-surface 3D movement, as we describe within ant nests. Therefore, we believe our approach will provide new methods for understanding both human design and the comparative biology of habitat spaces.This article is part of the theme issue 'Interdisciplinary approaches for uncovering the impacts of architecture on collective behaviour'.
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Affiliation(s)
- Tasos Varoudis
- Bartlett School of Architecture, University College London (UCL), 22 Gordon Street, London, WC1H 0QB, UK
| | - Abigail G Swenson
- Department of Biology, Providence College Providence, 1 Cunningham Square, Providence, RI 02918, USA
| | - Scott D Kirkton
- Department of Biological Sciences, Union College, 807 Union St, Schenectady, NY 12308, USA
| | - James S Waters
- Department of Biology, Providence College Providence, 1 Cunningham Square, Providence, RI 02918, USA
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15
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Ferral N, Holloway K, Li M, Yin Z, Hou C. Heterogeneous activity causes a nonlinear increase in the group energy use of ant workers isolated from queen and brood. INSECT SCIENCE 2018; 25:487-498. [PMID: 28019084 DOI: 10.1111/1744-7917.12433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 06/06/2023]
Abstract
Increasing evidence has shown that the energy use of ant colonies increases sublinearly with colony size so that large colonies consume less per capita energy than small colonies. It has been postulated that social environment (e.g., in the presence of queen and brood) is critical for the sublinear group energetics, and a few studies of ant workers isolated from queens and brood observed linear relationships between group energetics and size. In this paper, we hypothesize that the sublinear energetics arise from the heterogeneity of activity in ant groups, that is, large groups have relatively more inactive members than small groups. We further hypothesize that the energy use of ant worker groups that are allowed to move freely increases more slowly than the group size even if they are isolated from queen and brood. Previous studies only provided indirect evidence for these hypotheses due to technical difficulties. In this study, we applied the automated behavioral monitoring and respirometry simultaneously on isolated worker groups for long time periods, and analyzed the image with the state-of-the-art algorithms. Our results show that when activity was not confined, large groups had lower per capita energy use, a lower percentage of active members, and lower average walking speed than small groups; while locomotion was confined, however, the per capita energy use was a constant regardless of the group size. The quantitative analysis shows a direct link between variation in group energy use and the activity level of ant workers when isolated from queen and brood.
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Affiliation(s)
- Nolan Ferral
- Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
| | - Kyara Holloway
- Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
| | - Mingzhong Li
- Department of Computer Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
| | - Zhaozheng Yin
- Department of Computer Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
| | - Chen Hou
- Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
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16
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Saar M, Gilad T, Kilon-Kallner T, Rosenfeld A, Subach A, Scharf I. The interplay between maze complexity, colony size, learning and memory in ants while solving a maze: A test at the colony level. PLoS One 2017; 12:e0183753. [PMID: 28837675 PMCID: PMC5570381 DOI: 10.1371/journal.pone.0183753] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/10/2017] [Indexed: 11/18/2022] Open
Abstract
Central-place foragers need to explore their immediate habitat in order to reach food. We let colonies of the individually foraging desert ant Cataglyphis niger search for a food reward in a maze. We did so for three tests per day over two successive days and an additional test after a time interval of 4-20 days (seven tests in total). We examined whether the colonies reached the food reward faster, consumed more food and changed the number of workers searching over time, within and between days. Colonies' food-discovery time shortened within and between days, indicating that some workers learnt and became more efficient in moving through the maze. Such workers, however, also forgot and deteriorated in their food-discovery time, leveling off back to initial performance after about two weeks. We used mazes of increasing complexity levels, differing in the potential number of wrong turns. The number of workers searching increased with colony size. Food-discovery time also increased with colony size in complex mazes but not in simple ones, perhaps due to the more frequent interactions among workers in large colonies having to move through narrow routes. Finally, the motivation to solve the maze was probably not only the food reward, because food consumption did not change over time.
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Affiliation(s)
- Maya Saar
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tomer Gilad
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tal Kilon-Kallner
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Adar Rosenfeld
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Aziz Subach
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Inon Scharf
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
- * E-mail:
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17
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Stroeymeyt N, Joye P, Keller L. Polydomy enhances foraging performance in ant colonies. Proc Biol Sci 2017; 284:20170269. [PMID: 28446699 PMCID: PMC5413928 DOI: 10.1098/rspb.2017.0269] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 03/21/2017] [Indexed: 11/12/2022] Open
Abstract
Collective foraging confers benefits in terms of reduced predation risk and access to social information, but it heightens local competition when resources are limited. In social insects, resource limitation has been suggested as a possible cause for the typical decrease in per capita productivity observed with increasing colony size, a phenomenon known as Michener's paradox. Polydomy (distribution of a colony's brood and workers across multiple nests) is believed to help circumvent this paradox through its positive effect on foraging efficiency, but there is still little supporting evidence for this hypothesis. Here, we show experimentally that polydomy enhances the foraging performance of food-deprived Temnothorax nylanderi ant colonies via several mechanisms. First, polydomy influences task allocation within colonies, resulting in faster retrieval of protein resources. Second, communication between sister nests reduces search times for far away resources. Third, colonies move queens, brood and workers across available nest sites in response to spatial heterogeneities in protein and carbohydrate resources. This suggests that polydomy represents a flexible mechanism for space occupancy, helping ant colonies adjust to the environment.
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Affiliation(s)
- N Stroeymeyt
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015 Lausanne, Switzerland
| | - P Joye
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015 Lausanne, Switzerland
| | - L Keller
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015 Lausanne, Switzerland
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18
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Kohlmeier P, Negroni MA, Kever M, Emmling S, Stypa H, Feldmeyer B, Foitzik S. Intrinsic worker mortality depends on behavioral caste and the queens' presence in a social insect. Naturwissenschaften 2017; 104:34. [PMID: 28353195 DOI: 10.1007/s00114-017-1452-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/20/2017] [Accepted: 02/22/2017] [Indexed: 12/30/2022]
Abstract
According to the classic life history theory, selection for longevity depends on age-dependant extrinsic mortality and fecundity. In social insects, the common life history trade-off between fecundity and longevity appears to be reversed, as the most fecund individual, the queen, often exceeds workers in lifespan several fold. But does fecundity directly affect intrinsic mortality also in social insect workers? And what is the effect of task on worker mortality? Here, we studied how social environment and behavioral caste affect intrinsic mortality of ant workers. We compared worker survival between queenless and queenright Temnothorax longispinosus nests and demonstrate that workers survive longer under the queens' absence. Temnothorax ant workers fight over reproduction when the queen is absent and dominant workers lay eggs. Worker fertility might therefore increase lifespan, possibly due to a positive physiological link between fecundity and longevity, or better care for fertile workers. In social insects, division of labor among workers is age-dependant with young workers caring for the brood and old ones going out to forage. We therefore expected nurses to survive longer than foragers, which is what we found. Surprisingly, inactive inside workers showed a lower survival than nurses but comparable to that of foragers. The reduced longevity of inactive workers could be due to them being older than the nurses, or due to a positive effect of activity on lifespan. Overall, our study points to behavioral caste-dependent intrinsic mortality rates and a positive association between fertility and longevity not only in queens but also in ant workers.
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Affiliation(s)
- Philip Kohlmeier
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
| | - Matteo Antoine Negroni
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany
| | - Marion Kever
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany
| | - Stefanie Emmling
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany
| | - Heike Stypa
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany
| | - Barbara Feldmeyer
- Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, D-60325, Frankfurt am Main, Germany
| | - Susanne Foitzik
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany
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19
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Procter DS, Cottrell JE, Watts K, A'Hara SW, Hofreiter M, Robinson EJH. Does cooperation mean kinship between spatially discrete ant nests? Ecol Evol 2016; 6:8846-8856. [PMID: 28035273 PMCID: PMC5192893 DOI: 10.1002/ece3.2590] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Revised: 10/04/2016] [Accepted: 10/06/2016] [Indexed: 11/26/2022] Open
Abstract
Eusociality is one of the most complex forms of social organization, characterized by cooperative and reproductive units termed colonies. Altruistic behavior of workers within colonies is explained by inclusive fitness, with indirect fitness benefits accrued by helping kin. Members of a social insect colony are expected to be more closely related to one another than they are to other conspecifics. In many social insects, the colony can extend to multiple socially connected but spatially separate nests (polydomy). Social connections, such as trails between nests, promote cooperation and resource exchange, and we predict that workers from socially connected nests will have higher internest relatedness than those from socially unconnected, and noncooperating, nests. We measure social connections, resource exchange, and internest genetic relatedness in the polydomous wood ant Formica lugubris to test whether (1) socially connected but spatially separate nests cooperate, and (2) high internest relatedness is the underlying driver of this cooperation. Our results show that socially connected nests exhibit movement of workers and resources, which suggests they do cooperate, whereas unconnected nests do not. However, we find no difference in internest genetic relatedness between socially connected and unconnected nest pairs, both show high kinship. Our results suggest that neighboring pairs of connected nests show a social and cooperative distinction, but no genetic distinction. We hypothesize that the loss of a social connection may initiate ecological divergence within colonies. Genetic divergence between neighboring nests may build up only later, as a consequence rather than a cause of colony separation.
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Affiliation(s)
- Duncan S. Procter
- York Centre for Complex Systems Analysis & Department of BiologyUniversity of YorkYorkUK
- Centre for Exercise, Nutrition and Health SciencesSchool for Policy StudiesUniversity of BristolBristolUK
| | | | | | | | - Michael Hofreiter
- Institut für Biochemie und BiologieUniversität PotsdamPotsdamGermany
| | - Elva J. H. Robinson
- York Centre for Complex Systems Analysis & Department of BiologyUniversity of YorkYorkUK
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20
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Negroni MA, Jongepier E, Feldmeyer B, Kramer BH, Foitzik S. Life history evolution in social insects: a female perspective. CURRENT OPINION IN INSECT SCIENCE 2016; 16:51-57. [PMID: 27720050 DOI: 10.1016/j.cois.2016.05.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 05/11/2016] [Accepted: 05/11/2016] [Indexed: 06/06/2023]
Abstract
Social insects are known for their unusual life histories with fecund, long-lived queens and sterile, short-lived workers. We review ultimate factors underlying variation in life history strategies in female social insects, whose social life reshapes common trade-offs, such as the one between fecundity and longevity. Interspecific life history variation is associated with colony size, mediated by changes in division of labour and extrinsic mortality. In addition to the ratio of juvenile to adult mortality, social factors such as queen number influence life history trajectories. We discuss two hypotheses explaining why queen fecundity and lifespan is higher in single-queen societies and suggest further research directions on the evolution of life history variation in social insects.
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Affiliation(s)
- Matteo Antoine Negroni
- Institute of Zoology, Johannes Gutenberg University Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany
| | - Evelien Jongepier
- Institute of Zoology, Johannes Gutenberg University Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany
| | - Barbara Feldmeyer
- Senckenberg Biodiversity and Climate Research Centre (BiK-F), Molecular Ecology, Senckenberganlage 25, Frankfurt am Main 60325, Germany
| | - Boris H Kramer
- Theoretical Research in Evolutionary Life Sciences (TRES), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Susanne Foitzik
- Institute of Zoology, Johannes Gutenberg University Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
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21
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Mitrus S. Emigration speed and the production of sexuals in colonies of the ant Temnothorax crassispinus under high and low levels of disturbance. INSECTES SOCIAUX 2015; 63:127-134. [PMID: 26798159 PMCID: PMC4712248 DOI: 10.1007/s00040-015-0447-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 10/21/2015] [Accepted: 10/28/2015] [Indexed: 06/05/2023]
Abstract
A nest relocation is costly for social insects, and involves hazards. Emigrations were studied in Temnothorax crassispinus ant colonies, which inhabit ephemeral nest sites, and which frequently change their nests. In a laboratory experiment, ant colonies from one group were forced to change their nest sites 10 times over a ca. 3-month period, whilst colonies from the second group were forced to adopt this practice twice (on the beginning of May, and in the second half of July). Colonies of the ant from both the groups reduced their total emigration duration. However, the duration of the transport phase remained unchanged. In the case of colonies with higher level of disturbance, there was no relation between colony growth rate and energy allocation in sexual individuals, whilst a negative correlation between these parameters was present in group with lower level of disturbance. In colonies with lower level of disturbance, the investment in sexuals was not correlated with the number of workers at the end of the experiment, whereas such a correlation was demonstrated for colonies with higher level of disturbance. The disturbance, and thus necessity of frequent nest relocations, may be perceived by ants as a signal that nest sites are of a lower quality and may contribute to a change in energy allocation.
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Affiliation(s)
- S. Mitrus
- Laboratory of Evolution and Animal Ecology, Department of Biosystematics, Opole University, Oleska 22, 45-052 Opole, Poland
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22
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Kramer BH, Schrempf A, Scheuerlein A, Heinze J. Ant Colonies Do Not Trade-Off Reproduction against Maintenance. PLoS One 2015; 10:e0137969. [PMID: 26383861 PMCID: PMC4575186 DOI: 10.1371/journal.pone.0137969] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 08/24/2015] [Indexed: 11/22/2022] Open
Abstract
The question on how individuals allocate resources into maintenance and reproduction is one of the central questions in life history theory. Yet, resource allocation into maintenance on the organismic level can only be measured indirectly. This is different in a social insect colony, a "superorganism" where workers represent the soma and the queen the germ line of the colony. Here, we investigate whether trade-offs exist between maintenance and reproduction on two levels of biological organization, queens and colonies, by following single-queen colonies of the ant Cardiocondyla obscurior throughout the entire lifespan of the queen. Our results show that maintenance and reproduction are positively correlated on the colony level, and we confirm results of an earlier study that found no trade-off on the individual (queen) level. We attribute this unexpected outcome to the existence of a positive feedback loop where investment into maintenance (workers) increases the rate of resource acquisition under laboratory conditions. Even though food was provided ad libitum, variation in productivity among the colonies suggests that resources can only be utilized and invested into additional maintenance and reproduction by the colony if enough workers are available. The resulting relationship between per-capita and colony productivity in our study fits well with other studies conducted in the field, where decreasing per-capita productivity and the leveling off of colony productivity have been linked to density dependent effects due to competition among colonies. This suggests that the absence of trade-offs in our laboratory study might also be prevalent under natural conditions, leading to a positive association of maintenance, (= growth) and reproduction. In this respect, insect colonies resemble indeterminate growing organisms.
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Affiliation(s)
- Boris H. Kramer
- Max-Planck-Institute for Demographic Research, Konrad-Zuse-Str. 1, D-18055, Rostock, Germany
| | - Alexandra Schrempf
- Zoology / Evolutionary Biology lab, University of Regensburg, Universitätsstraße 31, D-93040, Regensburg, Germany
| | - Alexander Scheuerlein
- Max-Planck-Institute for Demographic Research, Konrad-Zuse-Str. 1, D-18055, Rostock, Germany
| | - Jürgen Heinze
- Zoology / Evolutionary Biology lab, University of Regensburg, Universitätsstraße 31, D-93040, Regensburg, Germany
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23
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Abstract
Senescence, the decline in physiological and behavioral function with increasing age, has been the focus of significant theoretical and empirical research in a broad array of animal taxa. Preeminent among invertebrate social models of aging are ants, a diverse and ecologically dominant clade of eusocial insects characterized by reproductive and sterile phenotypes. In this review, we critically examine selection for worker lifespan in ants and discuss the relationship between functional senescence, longevity, task performance, and colony fitness. We did not find strong or consistent support for the hypothesis that demographic senescence in ants is programmed, or its corollary prediction that workers that do not experience extrinsic mortality die at an age approximating their lifespan in nature. We present seven hypotheses concerning how selection could favor extended worker lifespan through its positive relationship to colony size and predict that large colony size, under some conditions, should confer multiple and significant fitness advantages. Fitness benefits derived from long worker lifespan could be mediated by increased resource acquisition, efficient division of labor, accuracy of collective decision-making, enhanced allomaternal care and colony defense, lower infection risk, and decreased energetic costs of workforce maintenance. We suggest future avenues of research to examine the evolution of worker lifespan and its relationship to colony fitness, and conclude that an innovative fusion of sociobiology, senescence theory, and mechanistic studies of aging can improve our understanding of the adaptive nature of worker lifespan in ants.
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Affiliation(s)
| | - James F A Traniello
- Department of Biology, Boston University, 5 Cummington Mall, Boston MA, 02215
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24
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Robinson EJ. Polydomy: the organisation and adaptive function of complex nest systems in ants. CURRENT OPINION IN INSECT SCIENCE 2014; 5:37-43. [PMID: 32846740 DOI: 10.1016/j.cois.2014.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 06/11/2023]
Abstract
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.
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Affiliation(s)
- Elva Jh Robinson
- Department of Biology, University of York, Heslington, York YO10 5DD, UK.
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25
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Mitrus S. The cavity-nest ant Temnothorax crassispinus prefers larger nests. INSECTES SOCIAUX 2014; 62:43-49. [PMID: 25598548 PMCID: PMC4291514 DOI: 10.1007/s00040-014-0372-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/22/2014] [Accepted: 09/23/2014] [Indexed: 06/04/2023]
Abstract
Colonies of the ant Temnothorax crassispinus inhabit mostly cavities in wood and hollow acorns. Typically in the field, nest sites that can be used by the ant are a limited resource. In a field experiment, it was investigated whether the ants prefer a specific size of nest, when different ones are available. In July 2011, a total of 160 artificial nests were placed in a beech-pine forest. Four artificial nests (pieces of wood with volume cavities, ca 415, 605, 730, and 980 mm3, respectively) were located on each square meter of the experimental plot. One year later, shortly before the emergence of new sexuals, the nests were collected. In July 2012, colonies inhabited more frequently bigger nests. Among queenright colonies, the ones which inhabited bigger nests had more workers. However, there was no relationship between volume of nest and number of workers for queenless colonies. Queenright colonies from bigger nests produced more sexual individuals, but there was no correlation between number of workers and sex allocation ratio, or between volume of nest and sex allocation ratio. In a laboratory experiment where ant colonies were kept in 470 and 860 mm3 nests, larger colonies allocated more energy to produce sexual individuals. The results of this study show the selectivity of T. crassispinus ants regarding the size of nest cavity, and that the nest volume has an impact on life history parameters.
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Affiliation(s)
- S. Mitrus
- Laboratory of Evolution and Animal Ecology, Department of Biosystematics, Opole University, Oleska 22, 45-052 Opole, Poland
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26
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Pamminger T, Foitzik S, Metzler D, Pennings PS. Oh sister, where art thou? Spatial population structure and the evolution of an altruistic defence trait. J Evol Biol 2014; 27:2443-56. [PMID: 25262856 DOI: 10.1111/jeb.12496] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 08/28/2014] [Accepted: 08/29/2014] [Indexed: 11/29/2022]
Abstract
The evolution of parasite virulence and host defences is affected by population structure. This effect has been confirmed in studies focusing on large spatial scales, whereas the importance of local structure is not well understood. Slavemaking ants are social parasites that exploit workers of another species to rear their offspring. Enslaved workers of the host species Temnothorax longispinosus have been found to exhibit an effective post-enslavement defence behaviour: enslaved workers were observed killing a large proportion of the parasites' offspring. As enslaved workers do not reproduce, they gain no direct fitness benefit from this 'rebellion' behaviour. However, there may be an indirect benefit: neighbouring host nests that are related to 'rebel' nests can benefit from a reduced raiding pressure, as a result of the reduction in parasite nest size due to the enslaved workers' killing behaviour. We use a simple mathematical model to examine whether the small-scale population structure of the host species could explain the evolution of this potentially altruistic defence trait against slavemaking ants. We find that this is the case if enslaved host workers are related to nearby host nests. In a population genetic study, we confirm that enslaved workers are, indeed, more closely related to host nests within the raiding range of their resident slavemaker nest, than to host nests outside the raiding range. This small-scale population structure seems to be a result of polydomy (e.g. the occupation of several nests in close proximity by a single colony) and could have enabled the evolution of 'rebellion' by kin selection.
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Affiliation(s)
- T Pamminger
- Institute of Zoology, Johannes Gutenberg University of Mainz, Mainz, Germany; School of Life Sciences, University of Sussex, Brighton, UK
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