Social insects and social amoebae

Gadagkar, Raghavendra; Bonner, John Tyler

doi:10.1007/bf02703057

Cited by 31 publications

(19 citation statements)

References 70 publications

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“…Such patterns and results will probably not be a surprise to researchers working on morphogenesis at the cellular level. Indeed, in this area many experiments show that self-assembly plays a key role in morphogenesis; examples include the restoration of a multicellular organism or tissue from a homogeneous mix of dissociated cells (Steinberg, 1993) and the aggregation and subsequent differentiation of individuals in social amoebae (Bonner, 1967;Gadagkar and Bonner, 1994). Thus, self-assembly is a beautiful example of a similar organisational mechanism operating at very different biological levels.…”

Section: Discussionmentioning

confidence: 99%

Self-assemblages in insect societies

2002

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In insect societies, a number of very striking collective structures are formed by individuals linking themselves to one another. One such example is an army ant bivouac. These structures are termed self-assemblages and are part of a more general and important aspect of insect societies -intermediate-level parts -in which functional grouplevel adaptive structures are formed. These parts are, in a sense, the tissues and organs of complex insect societies. Here we review the natural history of self-assemblages in insect societies. We find that at least 18 different types of structure exist: -assemblages are found in a variety of species of ants, bees, and wasps, but (as far as we are aware) not in termites. The function of these self-assemblages can be grouped under five broad categories which are not mutually exclusive: 1) defence, 2) pulling structures, 3) thermoregulation, 4) colony survival under inclement conditions, and 5) ease of passage when crossing an obstacle. The paucity of our knowledge concerning the factors that favour self-assemblage formation and the likely proximate mechanisms are highlighted.

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Section: Discussionmentioning

confidence: 99%

Self-assemblages in insect societies

2002

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“…Consistent with this prediction, organisms with very large aggregations, such as the treekilling bark beetles or the cliff swallows (table 3), lack reproductive specialization within their groups while organisms with reproductive specialization, such as the pleometrotic ants, form relatively small aggregations (table 3). Apparent exceptions to this trend are the cellular slime molds and the social bacteria that may form associations of dozens, hundreds, or thousands of cells but still exhibit extreme reproductive altruism (Bonner 1982;Rosenberg 1984;Gadagkar and Bonner 1994;Velicer et al 2000). In these cases, however, the relevant unit is not the number of cells but the number and proportional representation of clones forming part of the assemblages.…”

Section: Associations Among Nonrelatives and The Relative Fitness Cosmentioning

confidence: 91%

“…With a viscous population structure, just a few clones may dominate the assemblages. Alternatively, reproductive altruism in these organisms (or in the pleometrotic ants) could involve dissociation between genes and behavior, so that a lottery system decides who becomes a spore (or the sole reproductive) and who does not (Gadagkar and Bonner 1994). "Cheater" genotypes, however, have been identified in both cellular slime molds and social bacteria (Ennis et al 2000;Velicer et al 2000).…”

Section: Associations Among Nonrelatives and The Relative Fitness Cosmentioning

confidence: 96%

Population Ecology, Nonlinear Dynamics, and Social Evolution. I. Associations among Nonrelatives

Avilés

Abbot

Cutter

2002

The American Naturalist

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Using an individual-based and genetically explicit simulation model, we explore the evolution of sociality within a population-ecology and nonlinear-dynamics framework. Assuming that individual fitness is a unimodal function of group size and that cooperation may carry a relative fitness cost, we consider the evolution of one-generation breeding associations among nonrelatives. We explore how parameters such as the intrinsic rate of growth and group and global carrying capacities may influence social evolution and how social evolution may, in turn, influence and be influenced by emerging group-level and population-wide dynamics. We find that group living and cooperation evolve under a wide range of parameter values, even when cooperation is costly and the interactions can be defined as altruistic. Greater levels of cooperation, however, did evolve when cooperation carried a low or no relative fitness cost. Larger group carrying capacities allowed the evolution of larger groups but also resulted in lower cooperative tendencies. When the intrinsic rate of growth was not too small and control of the global population size was density dependent, the evolution of large cooperative tendencies resulted in dynamically unstable groups and populations. These results are consistent with the existence and typical group sizes of organisms ranging from the pleometrotic ants to the colonial birds and the global population outbreaks and crashes characteristic of organisms such as the migratory locusts and the tree-killing bark beetles.

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“…When the normally solitary amoebae are starved of their bacterial food source, they gather into a multicellular aggregate that forms a fruiting body. Here, Ϸ25% of cells altruistically die, forming a stalk that holds up the remaining cells, differentiated as spores, for dispersal (14)(15)(16)(17). Thus, unlike more familiar organisms that develop from one cell, development begins by aggregation of many dispersed cells.…”

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confidence: 99%

High relatedness maintains multicellular cooperation in a social amoeba by controlling cheater mutants

Gilbert

Foster

Mehdiabadi

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

242

302

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The control of cheating is important for understanding major transitions in evolution, from the simplest genes to the most complex societies. Cooperative systems can be ruined if cheaters that lower group productivity are able to spread. Kin-selection theory predicts that high genetic relatedness can limit cheating, because separation of cheaters and cooperators limits opportunities to cheat and promotes selection against low-fitness groups of cheaters. Here, we confirm this prediction for the social amoeba Dictyostelium discoideum; relatedness in natural wild groups is so high that socially destructive cheaters should not spread. We illustrate in the laboratory how high relatedness can control a mutant that would destroy cooperation at low relatedness. Finally, we demonstrate that, as predicted, mutant cheaters do not normally harm cooperation in a natural population. Our findings show how altruism is preserved from the disruptive effects of such mutant cheaters and how exceptionally high relatedness among cells is important in promoting the cooperation that underlies multicellular development.ooperation is a hallmark of major transitions in biological complexity: from molecules to genes, from genes to chromosomes, from primitive cells to complex cells, from cells to multicellular organisms, and from multicellular organisms to societies (1-3). Cooperative groups are vulnerable, however, to exploitation by cheaters, individuals that have access to group benefits without contributing their fair share (1-3). Among cells and individuals, high relatedness is thought to aid in selection against cheaters (4-6). High relatedness means that cheaters and cooperators will tend to be in different groups, which both limits opportunities for cheaters to exploit cooperators and exposes any group-level defects of cheaters to selection. Curiously, although such control is central to selfish-gene theory, tests at the genetic level have been limited by the kinds of information available. In large organisms, relatedness is often estimated, but cheater genes are unknown. In microorganisms, cheater genes can be found (7-13), but little is known about relatedness in natural social groups.The life cycle of social amoebae presents a challenge to the importance of relatedness in promoting selection against cheaters and an opportunity to test it. When the normally solitary amoebae are starved of their bacterial food source, they gather into a multicellular aggregate that forms a fruiting body. Here, Ϸ25% of cells altruistically die, forming a stalk that holds up the remaining cells, differentiated as spores, for dispersal (14-17). Thus, unlike more familiar organisms that develop from one cell, development begins by aggregation of many dispersed cells. Different clones can mix and cheat each other (18,19), for example by avoiding contributing to the sterile stalk (7). Models (20)(21)(22), experiments (7,23,24), and a natural observation (24), suggest that cooperative fruiting body formation can be threatened by the spread of mutant cheat...

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Social insects and social amoebae

Cited by 31 publications

References 70 publications

Self-assemblages in insect societies

Self-assemblages in insect societies

Population Ecology, Nonlinear Dynamics, and Social Evolution. I. Associations among Nonrelatives

High relatedness maintains multicellular cooperation in a social amoeba by controlling cheater mutants

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