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In social insects, the evolutionary stability of cooperation depends on the privileged relationships between individuals of the social group, which is facilitated by the recognition of relatives. Nestmate recognition is based on genetically determined cues and/or environmentally derived chemical components present on the cuticle of individuals. Here, we studied nestmate recognition in the ant Pheidole pallidula, a species where both single-queen (monogyne) and multiple-queen (polygyne) colonies co-occur in the same population. We combined geographical, genetic and chemical analyses to disentangle the factors influencing the level of intraspecific aggressiveness. We show that encounters between workers from neighbouring colonies (i.e. nests less than 5 m away) are on average less aggressive than those between workers from more distant colonies. Aggressive behaviour is associated with the level of genetic difference: workers from monogyne colonies are more aggressive than workers from polygyne colonies, and the intensity of aggressiveness is positively associated with the genetic distance between colonies. Since the genetic distance is correlated with the spatial distance between pairs of colonies, the lower level of aggression toward neighbours may result from their higher relatedness. In contrast, the analysis of overall cuticular hydrocarbon profiles shows that aggressive behaviour is associated neither with the chemical diversity of colonies, nor with the chemical distances between them. When considering methyl-branched alkanes only, however, chemical distances differed between monogyne and polygyne colonies and were significantly associated with aggressiveness. Altogether, these results show that the social structure of colonies and the genetic distances between colonies are two major factors influencing the intensity of agonistic behaviours in the ant P. pallidula., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience

Dans le nord-est de la France, 2 descendances maternelles d'epicea commun (Picea abies Karst.) sont cultivees en plantation pure et en melange dans un dispositif experimental original ou densite du peuplement et taux de melange varient de facon clinale (densite 200-10 000/ha, taux de melange 0%-100%). La descendance GANN 7 est nettement plus vigoureuse que MORZ 4. Pour les deux genotypes, la circonference atteinte 14 ans apres la plantation (hauteur moyenne 5 a 8 m) est fortement influencee par le gradient de densite (...)

International audience; After a rapid description of five gynogenetic unisexual species, this paper reviews themethods used for inducing gynogenesis in bisexual species.1) The frequency of male genome extrusion, very low after intraspecific mating, canbe appreciably increased in some particular interspecific combinations ; cold-shocking theeggs at the time of fertilization can also result in gynogenetic development. In the case, ofmammals, the male pronucleus can be microsurgically removed, but in most cases(amphibians, fish), haploid gynogenesis is induced by mutagenic treatment of the sperm(gamma, X, UV irradiation ; chemicals) before fertilization.2) Viable gynogenesis depends on the possibility of diploidizing the female geneticset ; several factors (oocyte aging, genetic factors, induction of ovulation) may beresponsible for the high frequency of « spontaneous » diploidization reported in somestudies. But diploid gynogenesis is generally obtained by induced retention of the secondpolar body or by induced suppression of the first cleavage, achieved by heat or pressuretreatment of eggs (fish and amphibins) or by the use of antimitotic chemicals (mammals).Diploid gynegenesis results in high inbreeding levels and original sex ratios. In thediscussion, we have tried to show that the objectives which stimulated its induction inamphibians have been frequently unattained or reached in other ways. In commercial fishspecies, gynogenesis may in the future contribute to the solution of major problems suchas genetic improvement and control of reproduction.

Intraspecific diffuse polymorphism is demonstrated, starting at Megacalanus princeps Wolfenden var. princeps, through M. princeps var. varius and ending at M. princeps var. inermis. For these different forms, the numbers of the maculae cribrosae are tabulated.