Chez les animaux sexués, les stratégies d'appariement et de dispersion sont influencées par de nombreux facteurs de l'environnement. Certains facteurs sont communs, ce qui suggère que ces deux stratégies n'évoluent pas indépendamment. Parmi ces facteurs, la structure génétique des populations pourrait jouer un rôle important dans cette évolution conjointe. Par une approche théorique, j'ai étudié l'évolution de la différence de dispersion entre les sexes en lien avec les stratégies d'appariement (monogamie, monoandrie, polyandrie). En monoandrie et polyandrie, stratégies où les deux sexes ont des nombres de partenaires différents, la compétition entre apparentés et la variation spatiale du succès reproducteur plus importante chez les mâles que les femelles, favorisent l'évolution d'une dispersion biaisée en faveur des mâles. Je me suis aussi intéressé à la place des gènes dans le génome et j'ai montré que la localisation de gènes de dispersion sur les chromosomes sexuels peut, à elle-seule, faire évoluer un différentiel de dispersion entre les sexes. J'ai exploré cette dernière possibilité dans le cadre de conflits génomiques potentiels. Parallèlement à cette approche théorique, j'ai effectué une étude expérimentale chez le lézard vivipare (Zootoca vivipara). J'ai recherché le rôle d'un effet maternel, médié par la corticostérone, sur le lien entre la stratégie d'appariement des femelles et la stratégie de dispersion de leurs jeunes. Je me suis aussi intéressé au coût de l'accouplement via la transmission de pathogènes entre partenaires. Mes résultats suggèrent l'absence d'effet direct des accouplements multiples sur la communauté bactérienne cloacale. / In sexually reproducing animals, dispersal and mating strategies are influenced by many environmental factors, some of these factors being common, which suggests that these two strategies could evolve jointly. Among these factors, population genetic structure could play a great role on this joint evolution. Using a theoretical approach, I studied how mating strategies (monogamy, monoandry, polyandry) can influence the evolution of sex-biased dispersal, with a particular focus on processes linked to relatedness. In monoandry and polyandry, i.e., strategies where both sexes have different numbers of mates, kin competition and a larger spatial variation in male than female reproductive success can lead to a male-biased dispersal. I have also investigated the importance of gene position in the genome and showed a link between dispersal genes and sex chromosomes can produce sex-biased dispersal. I have discussed this evolution of dispersal gene on sex chromosomes under a possible genomic conflict. In parallel to these theoretical studies, I have conducted an experimental study in the common lizard (Zootoca vivipara). I have investigated the role of maternal effect, through the influence of corticosterone, in the relationship between the mating strategy of females and the dispersal strategy of their offspring. I also tested experimentally the transmission of bacteria through mating in relation to the possible cost of transmission of pathogens. While I did not found any direct effect of multiple mating on cloacal bacterial community, my results suggest an effect due to a female response, which opens a new perspective in the study of the consequences of mating strategies.

A critical mechanism underpinning current biological diversity is the extent to which one species mates with, or avoids mating with, another. However, little is known about the factors that mediate hybridisation, especially during the initial and rarely observed stages of secondary contact when interspecific interactions have not responded to selection. In particular, whilst hybridisation is ultimately a behavioural phenomenon, the role of behaviour in mediating hybridisation and how it is influenced by environmental and circumstantial factors is rarely investigated. Recently introduced species provide us with unequalled opportunities to study these factors. In this thesis I examine the role of behavioural mechanisms, in particular male-male competition and mate choice, in mediating mating patterns between two genetically and phenotypically distinct lineages of European wall lizard (Podarcis muralis) that have come into recent secondary contact through human introductions. In Chapter Two, I investigated how sexual selection during allopatry is responsible for creating stark differences in phenotypic traits such as body size and weapon performance evident in the two lineages today, ultimately explaining the strong biases in dominance during territorial disputes between males. However, I also show that even given this asymmetry in male competitive ability, the extent to which it extrapolates into greater access to females in naturalistic, outdoor enclosures depends strongly on the spatial clustering of basking sites, a critically important resource for many ectotherms. In contrast to initial predictions suggested by asymmetries in male competition outlined in the previous chapter, in Chapter Three I show that both paternity and courtship behaviour was strongly assortative in the outdoor enclosures. Further investigation through staged experiments on olfactory mate choice, mating trials and analyses on specific behavioural data obtained in an enclosure experiment, I show that lineage based dominance actually contributes to assortative mating patterns in conjunction with weak conspecific male choice. In contrast, female choice seems to play no role in mediating the mating patterns observed between the two lineages. In Chapter Four I had the rare opportunity to examine the morphological and behavioural factors that predict why animals should hybridise in the first place, using the data obtained in the enclosure experiment above. I found that hybridisation was particularly common between small individuals of the larger lineage and large individuals of the smaller lineage; a result that corroborates the mechanisms determining the assortative patterns uncovered in Chapter Three. Additionally, hybridisation rates were particularly high in less dominant individuals, which I suggest is due to subordinate males having reduced opportunities for courting conspecific females due to male-male competition, requiring them to become less ‘choosy’ and therefore more likely to mate with heterospecifics. Finally, secondary contact cannot occur without at least one lineage coming into a new environment, and yet relatively little attention is paid to how this environmental change can affect the signals involved in intraspecific communication and mate choice. In Chapter Five I show that a change in the amount of time male lizards spend thermoregulating (a likely consequence of arriving in a new environment) significantly changes the chemical composition of their scent marks. However, whilst female lizards were able to detect these effects, they did not seem to base their mating decisions on them. Nevertheless, this result raises interesting questions about the potential function and consequences of this plasticity, and highlights the importance of considering plasticity in chemical communication in heterogeneous environments. Overall, this thesis shows the critically important role of behaviour in mediating intra- and interspecific mating patterns during recent secondary contact. In particular, it highlights how the direction and extent of hybridisation and competition are influenced by the degree to which differing morphological and behavioural phenotypes interact over a heterogeneous environment, particularly during the initial stage of secondary contact when mate choice has not had the chance to respond to the selective pressures of hybridisation.