Tactiques de reproduction et sélection sexuelle chez les ongulés<br /> Le cas d'une espèce territoriale avec faible dimorphisme sexuel de taille:<br /> le chevreuil européen (Capreolus Capreolus)
Co-tutelle entre:Laboratoire Comportement et Ecologie de la Faune Sauvage CEFS INRA UPR35Chemin de Borde-Rouge-Auzeville BP 52627 F-31326 Castanet-Tolosan cedexet Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences SLU, S-730 91, Riddarhyttan, SwedenThe aim of this study was to use for the first time molecular techniques (microsatellite genotyping and paternity analyses), in combination with field ecology studies, to provide data on male breeding success and identify the main determinants of variation in male breeding success in two long-term monitored populations of European roe deer Capreolus capreolus (Bogesund in Sweden and Trois Fontaines in France). The results show that males can sire up to 6 fawns per year and 14 fawns during their entire lifetime. As expected from the low level of sexual size dimorphism and the territorial mating system of roe deer, variance in male lifetime breeding success, and so opportunity for sexual selection, are lower than in highly dimorphic species such as red deer Cervus elaphus, suggesting a low polygyny level in roe deer. Males can successfully breed as young as 2 years of age, but breeding success of subadults is lower than that of older males. Successful breeding among sub-adults may be restricted to those high quality males that are able to defend a territory. Breeding success also tends to decline after 8 years of age (senescence), probably in relation to the loss of dominance. Male body mass and antler size positively affect male breeding success. It is known that antlers are used by males as a weapon in combats to defend their territory. However, my results also show that antler size is a honest signal of male phenotypic quality and may be used as a cue for rival males and females to assess male fighting ability, sexual vigor and/or phenotypic quality. In addition, male access to females and male breeding success are positively related to territory size, but not to habitat quality within a male's territory. Hence, the territorial mating system of roe deer differs from the conventional resource defense polygyny system and seems rather to conform to a "low risk low gain" strategy. Finally, using paternity analyses, I also provide evidence that multiple paternity is likely, but infrequent, in roe deer, suggesting that multiple mating among females may have evolved as a means to enhance fertilisation success. This study provides new insights into the evolution of mating systems and sexual selection in ungulates.Le but de cette étude était d'utiliser les techniques moléculaires dans deux populations de chevreuil, pour estimer la variance du succès reproducteur des mâles et identifier les principaux déterminants de cette variance. Comme attendu du fait de son faible dimorphisme sexuel, la variance dans le succès reproducteur à vie des mâles, et donc l'opportunité pour la sélection sexuelle, sont faibles chez le chevreuil, suggérant un faible degré de polygynie. Les mâles peuvent se reproduire dès 2 ans, mais avec un succès reproducteur inférieur à celui des mâles plus âgés. Le succès reproducteur tend aussi à décroître après 8 ans. La masse corporelle, la taille des bois, et la taille du territoire des mâles, affectent positivement leur succès reproducteur, mais pas la qualité de l'habitat dans leur territoire. Cette étude apporte de nouveaux éléments sur l'évolution de la territorialité et la sélection sexuelle chez les ongulés sauvages