Interaction conditions can change the balance of cooperation and conflict in multicellular groups... more Interaction conditions can change the balance of cooperation and conflict in multicellular groups. After aggregating together, cells of the social amoeba Dictyostelium discoideum may migrate as a group (known as a slug) to a new location. We consider this migration stage as an arena for social competition and conflict because the cells in the slug may not be from a genetically homogeneous population. In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition on fitness over the entire lifecycle. We compare slugs composed of either genetically homogenous or heterogeneous cells that have migrated or remained stationary in the social stage of the social amoeba Dictyostelium discoideum. After migration of chimeric slugs, we found that facultative cheating is reduced, where facultative cheating is defined as grea...
One condition for the evolution of altruism is genetic relatedness between altruist and beneficia... more One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here, we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum . We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift owing to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism.
One condition for the evolution of altruism is gen-etic relatedness between altruist and beneficia... more One condition for the evolution of altruism is gen-etic relatedness between altruist and beneficiary,often achieved through active kin recognition.Here, we investigate the power of a passive processresulting from genetic drift during populationgrowth in the social amoeba Dictyostelium discoi-deum. We put labelled and unlabelled cells of thesame clone in the centre of a plate, and allowedthem to proliferate outward. Zones formed by gen-etic drift owing to the small population of activelygrowing cells at the colony edge. We also found thatsingle cells could form zones of high relatedness.Relatedness increased at a significantly higher ratewhen food was in short supply. This study showsthat relatedness can be significantly elevatedbefore the social stage without a small foundingpopulation size or recognition mechanism.Keywords: social evolution; genetic drift;social microbes; Dictyostelium1. INTRODUCTIONThefitnessandsuccessofagroupofcooperatorsisunderconstantthreatofcollapsebytheinfiltratio...
During the course of field work in Scotland between 2006 and 2007 the numbers of elvers within th... more During the course of field work in Scotland between 2006 and 2007 the numbers of elvers within the substrate of a small coastal stream were estimated by sub-sampling using an FBA hand net. The total numbers of elvers caught over a three-day period in 2006 and 2007 were 139 and 396 respectively. These catches were equivalent to population densities of between 266.9 and 740.9 per 100m 2 of stream bed depending on the method employed to calculate density. Average catch rates varied from 0.15 up t o a maximum of 0.5 per sample. Although trivial in size compared to data derived from commercial fisheries there are no data currently available for migratory elvers on the west coast of Scotland. Given the cur rent demise of eels across Europe it is suggested that similar methods could usefully be employed more widely across Scotland to monitor the status of eel stocks.
Interaction conditions can change the balance of cooperation and conflict in multicellular groups... more Interaction conditions can change the balance of cooperation and conflict in multicellular groups. After aggregating together, cells of the social amoeba Dictyostelium discoideum may migrate as a group (known as a slug) to a new location. We consider this migration stage as an arena for social competition and conflict because the cells in the slug may not be from a genetically homogeneous population. In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition on fitness over the entire lifecycle. We compare slugs composed of either genetically homogenous or heterogeneous cells that have migrated or remained stationary in the social stage of the social amoeba Dictyostelium discoideum. After migration of chimeric slugs, we found that facultative cheating is reduced, where facultative cheating is defined as grea...
Dictyostelium has become a model organism for the study of social evolution because of the stage ... more Dictyostelium has become a model organism for the study of social evolution because of the stage in its life cycle where thousands of independent amoebae together form a fruiting body. Some individuals die to form a stalk that holds aloft the remaining cells for dispersal to new environments as spores. Different genotypes can aggregate together, creating opportunities for exploitation by cheaters that contribute a smaller proportion of cells to the stalk. Clustering of genotypes into separate fruiting bodies reduces the opportunities for cheating. Some genotypes achieve this by segregating after aggregation. Here we describe techniques for assaying cheating and segregation in D. discoideum. We cover how to grow and maintain cells, fluorescently label genotypes, design experiments for accuracy and precision, calculate fitness and segregation, and interpret the results.
Understanding the maintenance of cooperation requires an understanding of the nature of cheaters ... more Understanding the maintenance of cooperation requires an understanding of the nature of cheaters and the strategies used to mitigate their effects. However, it is often difficult to determine how cheating or differential social success has arisen. For example, cheaters may employ different strategies (e.g., fixed and facultative), whereas other causes of unequal fitness in social situations can result in winners and losers without cheating. To address these problems, we quantified the social success of naturally occurring genotypes of Dictyostelium discoideum during the formation of chimeric fruiting bodies, consisting of dead stalk cells and viable spores. We demonstrate that an apparent competitive dominance hierarchy of spore formation in chimera is partly due to a fixed strategy where genotypes exhibit dramatically different spore allocations. However, we also find complex, variable facultative strategies, where genotypes change their allocation in chimera. By determining the ma...
When individuals interact, phenotypic variation can be partitioned into direct genetic effects (D... more When individuals interact, phenotypic variation can be partitioned into direct genetic effects (DGEs) of the individuals' own genotypes, indirect genetic effects (IGEs) of their social partners' genotypes and epistatic interactions between the genotypes of interacting individuals ('genotype-by-genotype (GxG) epistasis'). These components can all play important roles in evolutionary processes, but few empirical studies have examined their importance. The social amoeba Dictyostelium discoideum provides an ideal system to measure these effects during social interactions and development. When starved, free-living amoebae aggregate and differentiate into a multicellular fruiting body with a dead stalk that holds aloft viable spores. By measuring interactions among a set of natural strains, we quantify DGEs, IGEs and GxG epistasis affecting spore formation. We find that DGEs explain most of the phenotypic variance (57.6%) whereas IGEs explain a smaller (13.3%) but highly significant component. Interestingly, GxG epistasis explains nearly a quarter of the variance (23.0%), highlighting the complex nature of genotype interactions. These results demonstrate the large impact that social interactions can have on development and suggest that social effects should play an important role in developmental evolution in this system.
The evolution of cooperation is a paradox because natural selection should favor exploitative ind... more The evolution of cooperation is a paradox because natural selection should favor exploitative individuals that avoid paying their fair share of any costs. Such conflict between the self-interests of cooperating individuals often results in the evolution of complex, opponent-specific, social strategies and counterstrategies. However, the genetic and biological mechanisms underlying complex social strategies, and therefore the evolution of cooperative behavior, are largely unknown. To address this dearth of empirical data, we combine mathematical modeling, molecular genetic, and developmental approaches to test whether variation in the production of and response to social signals is sufficient to generate the complex partnerspecific social success seen in the social amoeba Dictyostelium discoideum. Firstly, we find that the simple model of production of and response to social signals can generate the sort of apparent complex changes in social behavior seen in this system, without the ...
Interaction conditions can change the balance of cooperation and conflict in multicellular groups... more Interaction conditions can change the balance of cooperation and conflict in multicellular groups. After aggregating together, cells of the social amoeba Dictyostelium discoideum may migrate as a group (known as a slug) to a new location. We consider this migration stage as an arena for social competition and conflict because the cells in the slug may not be from a genetically homogeneous population. In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition on fitness over the entire lifecycle. We compare slugs composed of either genetically homogenous or heterogeneous cells that have migrated or remained stationary in the social stage of the social amoeba Dictyostelium discoideum. After migration of chimeric slugs, we found that facultative cheating is reduced, where facultative cheating is defined as grea...
One condition for the evolution of altruism is genetic relatedness between altruist and beneficia... more One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here, we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum . We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift owing to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism.
One condition for the evolution of altruism is gen-etic relatedness between altruist and beneficia... more One condition for the evolution of altruism is gen-etic relatedness between altruist and beneficiary,often achieved through active kin recognition.Here, we investigate the power of a passive processresulting from genetic drift during populationgrowth in the social amoeba Dictyostelium discoi-deum. We put labelled and unlabelled cells of thesame clone in the centre of a plate, and allowedthem to proliferate outward. Zones formed by gen-etic drift owing to the small population of activelygrowing cells at the colony edge. We also found thatsingle cells could form zones of high relatedness.Relatedness increased at a significantly higher ratewhen food was in short supply. This study showsthat relatedness can be significantly elevatedbefore the social stage without a small foundingpopulation size or recognition mechanism.Keywords: social evolution; genetic drift;social microbes; Dictyostelium1. INTRODUCTIONThefitnessandsuccessofagroupofcooperatorsisunderconstantthreatofcollapsebytheinfiltratio...
During the course of field work in Scotland between 2006 and 2007 the numbers of elvers within th... more During the course of field work in Scotland between 2006 and 2007 the numbers of elvers within the substrate of a small coastal stream were estimated by sub-sampling using an FBA hand net. The total numbers of elvers caught over a three-day period in 2006 and 2007 were 139 and 396 respectively. These catches were equivalent to population densities of between 266.9 and 740.9 per 100m 2 of stream bed depending on the method employed to calculate density. Average catch rates varied from 0.15 up t o a maximum of 0.5 per sample. Although trivial in size compared to data derived from commercial fisheries there are no data currently available for migratory elvers on the west coast of Scotland. Given the cur rent demise of eels across Europe it is suggested that similar methods could usefully be employed more widely across Scotland to monitor the status of eel stocks.
Interaction conditions can change the balance of cooperation and conflict in multicellular groups... more Interaction conditions can change the balance of cooperation and conflict in multicellular groups. After aggregating together, cells of the social amoeba Dictyostelium discoideum may migrate as a group (known as a slug) to a new location. We consider this migration stage as an arena for social competition and conflict because the cells in the slug may not be from a genetically homogeneous population. In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition on fitness over the entire lifecycle. We compare slugs composed of either genetically homogenous or heterogeneous cells that have migrated or remained stationary in the social stage of the social amoeba Dictyostelium discoideum. After migration of chimeric slugs, we found that facultative cheating is reduced, where facultative cheating is defined as grea...
Dictyostelium has become a model organism for the study of social evolution because of the stage ... more Dictyostelium has become a model organism for the study of social evolution because of the stage in its life cycle where thousands of independent amoebae together form a fruiting body. Some individuals die to form a stalk that holds aloft the remaining cells for dispersal to new environments as spores. Different genotypes can aggregate together, creating opportunities for exploitation by cheaters that contribute a smaller proportion of cells to the stalk. Clustering of genotypes into separate fruiting bodies reduces the opportunities for cheating. Some genotypes achieve this by segregating after aggregation. Here we describe techniques for assaying cheating and segregation in D. discoideum. We cover how to grow and maintain cells, fluorescently label genotypes, design experiments for accuracy and precision, calculate fitness and segregation, and interpret the results.
Understanding the maintenance of cooperation requires an understanding of the nature of cheaters ... more Understanding the maintenance of cooperation requires an understanding of the nature of cheaters and the strategies used to mitigate their effects. However, it is often difficult to determine how cheating or differential social success has arisen. For example, cheaters may employ different strategies (e.g., fixed and facultative), whereas other causes of unequal fitness in social situations can result in winners and losers without cheating. To address these problems, we quantified the social success of naturally occurring genotypes of Dictyostelium discoideum during the formation of chimeric fruiting bodies, consisting of dead stalk cells and viable spores. We demonstrate that an apparent competitive dominance hierarchy of spore formation in chimera is partly due to a fixed strategy where genotypes exhibit dramatically different spore allocations. However, we also find complex, variable facultative strategies, where genotypes change their allocation in chimera. By determining the ma...
When individuals interact, phenotypic variation can be partitioned into direct genetic effects (D... more When individuals interact, phenotypic variation can be partitioned into direct genetic effects (DGEs) of the individuals' own genotypes, indirect genetic effects (IGEs) of their social partners' genotypes and epistatic interactions between the genotypes of interacting individuals ('genotype-by-genotype (GxG) epistasis'). These components can all play important roles in evolutionary processes, but few empirical studies have examined their importance. The social amoeba Dictyostelium discoideum provides an ideal system to measure these effects during social interactions and development. When starved, free-living amoebae aggregate and differentiate into a multicellular fruiting body with a dead stalk that holds aloft viable spores. By measuring interactions among a set of natural strains, we quantify DGEs, IGEs and GxG epistasis affecting spore formation. We find that DGEs explain most of the phenotypic variance (57.6%) whereas IGEs explain a smaller (13.3%) but highly significant component. Interestingly, GxG epistasis explains nearly a quarter of the variance (23.0%), highlighting the complex nature of genotype interactions. These results demonstrate the large impact that social interactions can have on development and suggest that social effects should play an important role in developmental evolution in this system.
The evolution of cooperation is a paradox because natural selection should favor exploitative ind... more The evolution of cooperation is a paradox because natural selection should favor exploitative individuals that avoid paying their fair share of any costs. Such conflict between the self-interests of cooperating individuals often results in the evolution of complex, opponent-specific, social strategies and counterstrategies. However, the genetic and biological mechanisms underlying complex social strategies, and therefore the evolution of cooperative behavior, are largely unknown. To address this dearth of empirical data, we combine mathematical modeling, molecular genetic, and developmental approaches to test whether variation in the production of and response to social signals is sufficient to generate the complex partnerspecific social success seen in the social amoeba Dictyostelium discoideum. Firstly, we find that the simple model of production of and response to social signals can generate the sort of apparent complex changes in social behavior seen in this system, without the ...
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