Dataset for experiment 2

Dataset for experiment

Dataset for experiment 1: fly consumption

Dataset for experiment 1: fly consumptio

Dataset for experiment 3

Dataset for experiment

Prior experience and speed-accuracy trade-off (experiment 3), final state.

<p>(<b>A</b>) Number of colonies split (S, hashed bars) or having chosen the good (G, white bars) or mediocre nest (M, black bars) 24 hours after emigration onset. Nest choice patterns were compared between treatments using Fisher-Freeman-Halton's exact test and nest preference was tested within each treatment using exact binomial tests (ns: non-significant; ****: <i>p</i><0.001). (<b>B</b>) Reunification time for informed (light grey, n = 18) and naïve (dark grey, n = 18) colonies. Bars and whiskers represent the means and standard errors, respectively. The effect of treatment on reunification time was tested using GLMM (no data transformation).</p

Experimental design.

<p>Top view of the exploration arena consisting of one large, central dish; two small, intermediate dishes; and two small, peripheral dishes. Adjacent dishes were connected by tunnels for the ants to walk through. Conspicuous landmarks (black shapes) were used to help ants orientate inside the arena. Colonies housed in their old nest (ON) were positioned in the middle of the central dish. One or two available new nest sites (N1 and N2) were positioned in the peripheral dishes either at the onset of exploration (familiar nests) or at the onset of emigration (unfamiliar nests). The position of new nest sites (right or left) was pseudo-randomized between colonies.</p

Prior experience, nest choice and cohesiveness (experiment 2).

<p>Emigration data for informed (light grey, n = 33) and naïve (dark grey, n = 33) colonies emigrating to one familiar (F) and one unfamiliar (U) good nests or to two unfamiliar good nests (U1 and U2), respectively (experiment 2). Bars and whiskers represent the means and standard errors, respectively. (<b>A</b>) Discovery, assessment, transport and emigration times. <i>P-</i>values are given for the effect of nest site (familiar/unfamiliar) on discovery, assessment and transport times, and the effect of treatment (naïve/informed) on emigration time (GLMM; discovery time was log-transformed). Same letters indicate no statistical differences, whereas different letters indicate significant statistical differences (<i>p</i><0.05) in LSD post-hoc comparisons. (<b>B</b>) Number of successful forward tandem runs towards new nest sites. Same letters indicate no statistical differences, whereas different letters indicate significant statistical differences (<i>p</i><0.05) in LSD post-hoc comparisons (GLMM; effect of nest: <i>p</i><0.005; no data transformation). (<b>C</b>) Choosiness and Cohesiveness indexes. Choosiness was calculated as the proportion of items in the familiar nest (informed colonies) or in unfamiliar nest 1 (naïve colonies). <i>P</i>-values are given for the effect of treatment on both variables (GLMM; no data transformation). The broken line over choosiness – set at 0.5 – represents expectations under the hypothesis of random choice between both nests (*****: <i>p</i><0.001 in one-sample Wilcoxon test for non-normal data; ns: non-significant in one-sample t-test for normal data).</p

Prior experience and emigration speed (experiment 1).

<p>(<b>A–D</b>) Emigration data for informed (Inf., light grey, n = 24) and naïve (dark grey, n = 24) colonies emigrating to a single good nest site (experiment 1). Bars and whiskers represent the means and standard errors, respectively (A–B, D); full squares, rectangles, whiskers and open circles represent the median, interquartile range, 1.5 x interquartile range and outliers, respectively (C). (<b>A</b>) Discovery, assessment, transport and emigration times. The effect of treatment on each variable was tested using GLMM (no data transformation). (<b>B</b>) Crossing times of intermediate dishes leading either to the new nest site or to the dead-end. Same letters indicate no statistical differences, whereas different letters indicate significant statistical differences (<i>p</i><0.05) in LSD post-hoc comparisons (GLMM, interaction treatment/direction: <i>p</i> = 0.059; no data transformation). (<b>C</b>) Number of successful forward tandem runs to the new nest site (Wilcoxon matched-pairs test). (<b>D</b>) Quorum thresholds used to switch to transport. The effect of treatment on quorum threshold was tested using GLMM (no data transformation). (<b>E</b>) Relationships between the number of ants in the familiar nest at the onset of emigration and, respectively, the quorum threshold (left) or the assessment time (right) for informed colonies (n = 24). Linear regression shows that these relationships are best described by the following equations: (i) Quorum Threshold  = 2.422+1.059 x No. of ants, <i>r²</i> = 0.82, <i>p</i><0.001; and (ii) Assessment time  = 5.3+0.171 x No. of ants, <i>r²</i> = 0.048, <i>p</i> = 0.301.</p

Experimental protocols.

<p>Total number of colonies used in the experiment (<i>n</i>) and in the final data analysis (<i>n</i>'); quality of the old nest; and number and quality of available nest sites during exploration and emigration for each experiment and each treatment (when applicable). For the emigration phase, it is indicated whether new nest sites are familiar (F) or unfamiliar (U).</p

Effect of exposure to alien colony odor on nestmate recognition.

<p>(<b>A</b>) Experimental design. Workers from colony X were exposed to the odor of either nestmates (X_X) or non-nestmates from colony Y (X_Y), either inside sub-colonies during 24 hours (experiment 1) or directly on their antennae during 18 hours (experiment 2). Aggression tests between treated workers and anaesthetized target workers from colonies X, Y or unrelated alien Z were performed immediately after exposure as indicated by the arrows. (<b>B</b>) Restrained worker in the antennal exposure device. The picture shows CHC-coated glass capillaries positioned around the worker's antennae. (<b>C, D</b>) Aggression level of treated workers towards targets from colonies X (yellow bars), Y (blue bars) and Z (black bars) in experiments 1 (C) and 2 (D). Columns and error bars indicate mean and standard error of aggression indices respectively. Different letters indicate significant differences between categories (mixed-effects model with least square means post-hoc comparisons, <i>P</i><0.05). X_Y workers were significantly less aggressive towards non-nestmates from colony Y than X_X workers (X_Y–Y <i>vs.</i> X_X–Y: <i>P</i><0.0001 in both experiments). However, treatments did not influence aggressiveness towards nestmates (X_X–X <i>vs.</i> X_Y–X, experiment 1: <i>P</i> = 0.808; experiment 2: <i>P</i> = 0.837) or non-nestmates from colony Z (X_X–Z <i>vs.</i> X_Y–Z, experiment 1: <i>P</i> = 0. 322; experiment 2: <i>P</i> = 0. 416).</p

Effect of unilateral antennal exposure to alien colony odor.

<p>(<b>A</b>) Experimental design. Antennae of workers from colony X were inserted into two capillaries (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012377#pone-0012377-g001" target="_blank">Figure 1B</a>), one of which was treated with solvent (sham exposed, −) while the other was coated with CHCs (CHC-exposed, +) from either nestmate workers (control X_X) or non-nestmates from colony Y (test X_Y). After 18-hour exposure, one antenna was selectively excised. Aggression tests between treated workers and anaesthetized target workers from colonies X or Y were performed immediately after excision as indicated by the arrows. (<b>B</b>) Aggression level of treated workers towards targets from colonies X (yellow bars) and Y (blue bars). Columns and error bars indicate mean and standard error of aggression indices respectively. Different letters indicate significant differences between categories (mixed-effects model with least square means post-hoc comparisons, <i>P</i><0.05). When their remaining antenna had been exposed to non-nestmate CHCs (X_Y⁺), workers were significantly less aggressive towards non-nestmates from colony Y than when their remaining antenna had been sham exposed (X_Y⁺–Y <i>vs.</i> X_Y⁻–Y, <i>P</i><0.0001). X_Y⁺ workers were also less aggressive towards Y-individuals than control workers, which had been exposed to nestmate odor (X_Y⁺–Y <i>vs.</i> X_X⁺–Y, <i>P</i><0.0001; X_Y⁺–Y <i>vs.</i> X_X⁻–Y, <i>P</i><0.0001). The aggressiveness of control workers (X_X) towards Y-individuals was always high and did not depend on which antenna was excised (X_X⁺–Y <i>vs.</i> X_X⁻–Y, <i>P</i> = 0.821).</p