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Behavioural Contagion Explains Group Cohesion in a Social Crustacean.

Broly P, Deneubourg JL - PLoS Comput. Biol. (2015)

Bottom Line: In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living.The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment.Our results indicate that the response to the disturbance of groups decreases with increases in these two variables.

View Article: PubMed Central - PubMed

Affiliation: Unité d'Ecologie Sociale, Université Libre de Bruxelles, Campus de la Plaine, Bruxelles, Belgium; Laboratoire Ecologie et Biodiversité, Faculté de Gestion, Economie & Science, UCLILLE, Université Lille Nord de France, Lille, France.

ABSTRACT
In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living. The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment. In this view, social aggregation in terrestrial isopods represents an interesting model due to its recurrence both in the field and in the laboratory. In this study, and under a perturbation context, we experimentally tested the stability of groups of woodlice according to group size and time spent in group. Our results indicate that the response to the disturbance of groups decreases with increases in these two variables. Models neglecting social effects cannot reproduce experimental data, attesting that cohesion of aggregation in terrestrial isopods is partly governed by a social effect. In particular, models involving calmed and excited individuals and a social transition between these two behavioural states more accurately reproduced our experimental data. Therefore, we concluded that group cohesion (and collective response to stimulus) in terrestrial isopods is governed by a transitory resting state under the influence of density of conspecifics and time spent in group. Lastly, we discuss the nature of direct or indirect interactions possibly implicated.

No MeSH data available.


Calculated experimental and theoretical fraction of slow individuals Fs according to number of initially introduced individuals (a) and the retention time of groups (b).
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pcbi.1004290.g004: Calculated experimental and theoretical fraction of slow individuals Fs according to number of initially introduced individuals (a) and the retention time of groups (b).

Mentions: We assumed that α, β and μ are constant and independent of the conditions (total number of individuals or retention time). We performed a numerical resolution of this master equation, and at the end of the retention period, the model predicts the probability Θ (S) of having a population of S individuals in the slow state, and a mean value of <S> or the mean theoretical fraction of slow individual (Fs). For each condition, we searched for parameter values of α, β and μ for which the theoretical mean values of Fs is the closest to experimental mean values of Fs. The results give α = 10–4s-1; β = 2,5.10–4s-1; and μ = 9.10–4s-1. For all conditions, the mean fraction of slow individuals Fs observed is particularly close to the Fs obtained with the model that is described here (Fig 4).


Behavioural Contagion Explains Group Cohesion in a Social Crustacean.

Broly P, Deneubourg JL - PLoS Comput. Biol. (2015)

Calculated experimental and theoretical fraction of slow individuals Fs according to number of initially introduced individuals (a) and the retention time of groups (b).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465910&req=5

pcbi.1004290.g004: Calculated experimental and theoretical fraction of slow individuals Fs according to number of initially introduced individuals (a) and the retention time of groups (b).
Mentions: We assumed that α, β and μ are constant and independent of the conditions (total number of individuals or retention time). We performed a numerical resolution of this master equation, and at the end of the retention period, the model predicts the probability Θ (S) of having a population of S individuals in the slow state, and a mean value of <S> or the mean theoretical fraction of slow individual (Fs). For each condition, we searched for parameter values of α, β and μ for which the theoretical mean values of Fs is the closest to experimental mean values of Fs. The results give α = 10–4s-1; β = 2,5.10–4s-1; and μ = 9.10–4s-1. For all conditions, the mean fraction of slow individuals Fs observed is particularly close to the Fs obtained with the model that is described here (Fig 4).

Bottom Line: In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living.The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment.Our results indicate that the response to the disturbance of groups decreases with increases in these two variables.

View Article: PubMed Central - PubMed

Affiliation: Unité d'Ecologie Sociale, Université Libre de Bruxelles, Campus de la Plaine, Bruxelles, Belgium; Laboratoire Ecologie et Biodiversité, Faculté de Gestion, Economie & Science, UCLILLE, Université Lille Nord de France, Lille, France.

ABSTRACT
In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living. The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment. In this view, social aggregation in terrestrial isopods represents an interesting model due to its recurrence both in the field and in the laboratory. In this study, and under a perturbation context, we experimentally tested the stability of groups of woodlice according to group size and time spent in group. Our results indicate that the response to the disturbance of groups decreases with increases in these two variables. Models neglecting social effects cannot reproduce experimental data, attesting that cohesion of aggregation in terrestrial isopods is partly governed by a social effect. In particular, models involving calmed and excited individuals and a social transition between these two behavioural states more accurately reproduced our experimental data. Therefore, we concluded that group cohesion (and collective response to stimulus) in terrestrial isopods is governed by a transitory resting state under the influence of density of conspecifics and time spent in group. Lastly, we discuss the nature of direct or indirect interactions possibly implicated.

No MeSH data available.