Complex interactions underpin social behaviour in Dictyostelium giganteum

Sathe, Santosh and Nanjundiah, Vidyanand (2018) Complex interactions underpin social behaviour in Dictyostelium giganteum. In: BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY, 72 (10).

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Abstract

In the wild, social groups of the cellular slime mould amoeba Dictyostelium giganteum are genetically heterogeneous more often than not. When studied as 1:1 binary mixes, amoebae of one strain almost always form more spores than the other, an observation that leads one to wonder what might be responsible for the long-term persistence of different strains in nature. We have monitored a number of individual and collective traits bearing on reproductive fitness in chimaeras of Dictyostelium giganteum obtained by mixing pairs of starved amoebae belonging to distinct wild-type strains in proportions ranging from 1:9 to 9:1. The main findings are that intercellular interactions take place at more than one stage of the life cycle and that generalisations drawn after mixing cells only in a 1:1 ratio can be misleading. A strain that does better than another in respect of some component of fitness (for example, spore formation) may do worse in respect of a different component (for example, growth rate). Also, a strain that is a more efficient sporulator than a second strain in one context may be less efficient in another context. In addition to such trade-offs, spore formation in chimaeras can exhibit negative frequency dependence, which too can lead to stable co-existence.Significance statementHumans live in social groups whose members perform different but equally important tasks. When they do so freely, the long-term stability of the group depends on give and take (trade-offs') between individuals who are generally unrelated. In contrast, studies of cooperation in non-human animals have focussed on relatedness through common descent as responsible for the maintenance of group cohesion. But animal groups too contain unrelated individuals. Using the example of a social amoeba, we show that this need not rule out a high level of cooperation including so-called altruism, as long as inter-individual interactions permit it. In both genetically homogeneous and heterogeneous groups, interactions can result in trade-offs between different traits. In genetically heterogeneous groups, they can also lead to a negative correlation between the efficiency with which cells of a genotype reproduce and the proportion of cells belonging to that genotype.

Item Type:	Journal Article
Publication:	BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY
Publisher:	SPRINGER
Additional Information:	Copy right for this article belong to SPRINGER
Keywords:	Altruism; Complex interactions; Dictyostelium; Slime moulds; Social amoebae; Trade-offs
Department/Centre:	Division of Biological Sciences > Centre for Ecological Sciences Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited:	16 Oct 2018 14:23
Last Modified:	16 Oct 2018 14:23
URI:	http://eprints.iisc.ac.in/id/eprint/60887

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