Phylogénie Et Evolution Du Comportement Social Chez Les Blattes ...

Ev o l u t i o n d u c o m p o r t e m e n t s o c i a lRESULTSTolerance to crowdingNearest neighbor distances were measured and analyzed for every species (Fig. 2) butdata from Parasphaeria were not included in statistical tests (cf. different protocol). P.n., L.e.and S.l., maintained very low distances to their conspecifics. The medians m of these threedistance distributions are very similar (respectively 0.2 cm, 0.15 cm and 0.1 cm). The lastspecies, T.a., maintained also small but higher distances (m = 0.4 cm). The median test formultiple sample requires the determination of the grand median M of all observations in all 4samples considered together (here M = 0.25). A significant difference was observed betweenthe four samples (χ 2 = 7.815; P < 0.001). The Tukey-type multiple comparison test showedthat the median of T.a. was significantly higher than those of P.n, L.e and S.l. (q T.a.-P.n.= 8.18, P< 0.001; q T.a.-L.e.= 5.92, P < 0.001 and q T.a.-S.l.= 5.08, P < 0.01), and that these three latter werenot statistically different from each other. This difference is mainly explained by the numberof individuals in contact (i.e. NND = 0): six dyads were observed in P.n., five dyads and twotriads in S.l., six dyads, one tetrad and one heptad in L.e., and only three dyads in T.a. Nearestneighbor distances for P.b. are shown as an information in Fig. 2, with a median of 1.2 cm.Interestingly, the modal value of NND for this species is 0 cm, as for other gregarious species.Dyadic interactionsTwenty different acts were identified from the behavioral sequences of the differentspecies (Table I). The size of the repertoire was slightly different among species: 15 acts forP.n. and L.e., 17 acts for T.a., 18 acts for P.b., and 19 acts for S.l. (Table II). No behavioral actwas exclusive to a single species and only three acts were common to only two species: “butt”and “body leaning” which are displayed by P.b. and S.l., and “bite” displayed by S.l. andT.a. Sixty-seven experiments were done and a total amount of 729 sequences was observed.Basically, a behavioral sequence is composed of six or seven acts (Table II). The mean322