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Individual preferences and social interactions determine the aggregation of woodlice.

Devigne C, Broly P, Deneubourg JL - PLoS ONE (2011)

Bottom Line: Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals.Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences.

View Article: PubMed Central - PubMed

Affiliation: Université Lille Nord de France, Lille, France. cedric.devigne@icl-lille.fr

ABSTRACT

Background: The aggregation of woodlice in dark and moist places is considered an adaptation to land life and most studies are focused on its functionality or on the behavioural mechanisms related to the individual's response to abiotic factors. Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.

Methodology/main findings: We present the dynamics of aggregation, not previously described in detail in literature, as being independent of the experimental conditions: homogeneous and heterogeneous environments with identical or different shelters. Indeed whatever these conditions, the aggregation is very quick. In less than 10 minutes more than 50% of woodlice were aggregated in several small groups in the homogeneous environment or under shelters in the heterogeneous environment. After this fast aggregation, woodlice progressively moved into a single aggregate or under one shelter.

Conclusions/significance: Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals. Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences. This inter-attraction can lead to situations that could seem sub-optimal.

Show MeSH
Comparison of dynamics of aggregation in homogeneous set ups.Dynamics were observed in arenas under low, medium, or high brightness corresponding to experimental conditions A, B, and C. a: total population of aggregated woodlice; b: woodlice aggregated in the final aggregate. Standard deviations are presented for each 3 minutes. The bottom part of the graphic represents the statistical differences obtained minute per minute using Dunn's test, p<0.05: lines show differences.
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pone-0017389-g003: Comparison of dynamics of aggregation in homogeneous set ups.Dynamics were observed in arenas under low, medium, or high brightness corresponding to experimental conditions A, B, and C. a: total population of aggregated woodlice; b: woodlice aggregated in the final aggregate. Standard deviations are presented for each 3 minutes. The bottom part of the graphic represents the statistical differences obtained minute per minute using Dunn's test, p<0.05: lines show differences.

Mentions: Whatever the experimental conditions, aggregation was very quick; more than 50% of the woodlice were observed in an aggregate in less than 10 minutes (Figure 3a). The main difference in aggregation dynamics occurred between experiments under high and the two others brightness settings. Indeed, in the first 15 minutes, global aggregation was faster in high brightness than in medium or low brightness (Figure 3a; Kruskal-Wallis test, KW values>6.66, p<0.05 followed by Dunn's test: C≠B and C≠A, p < 0.05). After 15 minutes, no differences were found except at the end of experiments where the total population of aggregated woodlice was significantly lower under high brightness than in the two other conditions (Figure 3a; Kruskal-Wallis test, KW values>6.66, p<0.05 followed by Dunn's test, p<0.05 in the final 5 minutes). Hence, in high brightness, after reaching a maximum very quickly, the number of aggregated woodlice progressively decreased during the experiments (Figure 3a; comparison between 10, 30, and 45 minutes; Friedman's test, Fr = 11.68, df = 2, p<0.01). By contrast, in low and medium brightness, after a rapid increase in the first 10 minutes, this number slowly but significantly continued to increase until the end of the experiments (Figure 3a; comparison between 10, 30, and 45 minutes; Friedman's test, Fr = 21.12 and 10.49, df = 2 for low and medium brightness respectively, p<0.01).


Individual preferences and social interactions determine the aggregation of woodlice.

Devigne C, Broly P, Deneubourg JL - PLoS ONE (2011)

Comparison of dynamics of aggregation in homogeneous set ups.Dynamics were observed in arenas under low, medium, or high brightness corresponding to experimental conditions A, B, and C. a: total population of aggregated woodlice; b: woodlice aggregated in the final aggregate. Standard deviations are presented for each 3 minutes. The bottom part of the graphic represents the statistical differences obtained minute per minute using Dunn's test, p<0.05: lines show differences.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3045452&req=5

pone-0017389-g003: Comparison of dynamics of aggregation in homogeneous set ups.Dynamics were observed in arenas under low, medium, or high brightness corresponding to experimental conditions A, B, and C. a: total population of aggregated woodlice; b: woodlice aggregated in the final aggregate. Standard deviations are presented for each 3 minutes. The bottom part of the graphic represents the statistical differences obtained minute per minute using Dunn's test, p<0.05: lines show differences.
Mentions: Whatever the experimental conditions, aggregation was very quick; more than 50% of the woodlice were observed in an aggregate in less than 10 minutes (Figure 3a). The main difference in aggregation dynamics occurred between experiments under high and the two others brightness settings. Indeed, in the first 15 minutes, global aggregation was faster in high brightness than in medium or low brightness (Figure 3a; Kruskal-Wallis test, KW values>6.66, p<0.05 followed by Dunn's test: C≠B and C≠A, p < 0.05). After 15 minutes, no differences were found except at the end of experiments where the total population of aggregated woodlice was significantly lower under high brightness than in the two other conditions (Figure 3a; Kruskal-Wallis test, KW values>6.66, p<0.05 followed by Dunn's test, p<0.05 in the final 5 minutes). Hence, in high brightness, after reaching a maximum very quickly, the number of aggregated woodlice progressively decreased during the experiments (Figure 3a; comparison between 10, 30, and 45 minutes; Friedman's test, Fr = 11.68, df = 2, p<0.01). By contrast, in low and medium brightness, after a rapid increase in the first 10 minutes, this number slowly but significantly continued to increase until the end of the experiments (Figure 3a; comparison between 10, 30, and 45 minutes; Friedman's test, Fr = 21.12 and 10.49, df = 2 for low and medium brightness respectively, p<0.01).

Bottom Line: Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals.Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences.

View Article: PubMed Central - PubMed

Affiliation: Université Lille Nord de France, Lille, France. cedric.devigne@icl-lille.fr

ABSTRACT

Background: The aggregation of woodlice in dark and moist places is considered an adaptation to land life and most studies are focused on its functionality or on the behavioural mechanisms related to the individual's response to abiotic factors. Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.

Methodology/main findings: We present the dynamics of aggregation, not previously described in detail in literature, as being independent of the experimental conditions: homogeneous and heterogeneous environments with identical or different shelters. Indeed whatever these conditions, the aggregation is very quick. In less than 10 minutes more than 50% of woodlice were aggregated in several small groups in the homogeneous environment or under shelters in the heterogeneous environment. After this fast aggregation, woodlice progressively moved into a single aggregate or under one shelter.

Conclusions/significance: Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals. Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences. This inter-attraction can lead to situations that could seem sub-optimal.

Show MeSH