Elsevier

Animal Behaviour

Volume 123, January 2017, Pages 101-106
Animal Behaviour

Indirect genetic effects on the sociability of several group members

https://doi.org/10.1016/j.anbehav.2016.10.028Get rights and content

Highlights

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    Indirect genetic effects (IGEs) are a major driver of social evolution.

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    We examined how stimulus genotypes influence sociability of several focals.

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    Focals' sociability was significantly affected by the stimulus genotypes.

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    A mechanism mediating this effect was the encounter rate between focal flies.

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    Focals' encounter rates were lower when grouped with more cohesive stimulus flies.

Indirect genetic effects (IGEs) are a major driver of social evolution, but much of the experimental work pertaining to IGEs on social behaviour has focused on the effect of stimulus individuals on single focal individuals. We extended IGE research to examine how stimulus individuals influence social interactions among several focal individuals. Specifically, we relied on recent work on social behaviour in fruit flies to examine whether IGEs cause 12 stimulus flies of distinct genotypes to alter social interactions within groups of six focal flies. The social behaviour of focals was significantly affected by the genotype of the stimulus flies. Focals were closer together when grouped with stimulus flies from genotypes that were close together than when grouped with stimulus flies from genotypes that were farther apart. A mechanism mediating this effect was the encounter rate between focal flies, which was lowest when the focal flies were grouped with stimulus flies of the more cohesive genotypes.

Section snippets

General

We maintained all populations at low density in 40 ml vials each containing 5 ml of standard food (1 litre of which contained 90 g of sucrose, 32 g of yeast, 75 g of cornmeal, 20 g of agar and 2 g of methyl paraben), at 25 °C and 60% relative humidity, on a 12:12 h light cycle with lights on at 1000 hours. These conditions are optimal for fruit fly well-being. Furthermore, we handled flies either by gentle aspiration or with a soft brush following brief anaesthetization with CO2, and applied no harmful

Results

In the preliminary experiment, there was a significant effect of stimulus fly genotype on average nearest-neighbour index (χ22 = 74.4, P < 0.001; Fig. 1b). A post hoc analysis of experiment 1 with stimulus male nearest-neighbour index as a response variable showed commensurate differences between genotypes (χ22 = 141.0, P < 0.001; Fig. 1c). Most importantly, the average nearest-neighbour index of focal flies differed significantly based on the genotype of the stimulus flies they were paired with, with

Discussion

Our major finding was that social behaviour within a group of six focal group members varied as a function of the genotype of 12 other stimulus individuals (Fig. 1). As far as we know, this is the first study that documents IGEs caused by stimulus individuals on the social dynamics among several focal group members. The most relevant previous work involved applied research in a few species of farm animals housed in groups with the goal of reducing overall stress, injury and mortality, and

Acknowledgments

We thank L. Dukas, T. Sherratt and two anonymous referees for comments on the manuscript, A. Nguyen for assistance, and the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation and Ontario Ministry of Research and Innovation for funding.

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    • Cited by (0)

    1

    E-mail address: [email protected] (B. B. Anderson).

    2

    E-mail address: [email protected] (A. Scott).

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