The sex chromosome system can influence the evolution of sex-biased dispersal.

Sex-biased dispersal is a much-discussed feature in literature on dispersal. Diverse hypotheses have been proposed to explain the evolution of sex-biased dispersal, a difference in dispersal rate or dispersal distance between males and females. An early hypothesis has indicated that it may rely on the difference in sex chromosomes between males and females. However, this proposal was quickly rejected without a real assessment. We propose a new perspective on this hypothesis by investigating the evolution of sex-biased dispersal when dispersal genes are sex-linked, that is when they are located on the sex chromosomes. We show that individuals of the heterogametic sex disperse relatively more than do individuals of the homogametic sex when dispersal genes are sex-linked rather than autosomal. Although such a sex-biased dispersal towards the heterogametic sex is always observed in monogamous species, the mating system and the location of dispersal genes interact to modulate sex-biased dispersal in monandry and polyandry. In the context of the multicausality of dispersal, we suggest that sex-linked dispersal genes can influence the evolution of sex-biased dispersal.

Female choice for heterozygous mates changes along successive matings in a lizard.

Female mate choice and female multiple mating are major focuses of studies on sexual selection. In a multiple mating context, the benefits of mate choice can change along successive matings, and female choice would be expected to change accordingly. We investigated sequential female mate choice in the moderately polyandrous common lizard (Zootoca vivipara, synonym Lacerta vivipara). Along successive mating opportunities, we found that females were relatively unselective for the first mate, but accepted males of higher heterozygosity for subsequent mating, consistent with the trade-up choice hypothesis. We discuss the evidence of trade-up mate choice in squamates and generally trade-up for mate heterozygosity in order to motivate new studies to fill gaps on these questions.

Relationship between female mating strategy, litter success and offspring dispersal.

The relationship between mating systems and dispersal has generally been studied at the population and species levels. It has hardly ever been investigated at the individual level, by studying the variations of mating and dispersal strategies between individuals. We investigated this relationship in a natural population of the common lizard (Lacerta vivipara). Assuming that dispersal has a genetic basis, juvenile dispersal would be expected to be more family-dependent in monoandrous litters than in polyandrous litters. The opposite pattern was observed. Thus, maternal effects and/or litter effects play a greater role than genetic determinism in shaping the dispersal phenotype of juveniles. Moreover, the relationship between female mating strategy and offspring dispersal depended on litter success, in a way consistent with an influence of mother-offspring competition. Such a link between mating and dispersal strategies of individuals may have major repercussions for the way we consider the roles of these processes in population functioning.

Condition dependence of reproductive strategy and the benefits of polyandry in a viviparous lizard.

Species in which males do not contribute to reproduction beyond the provision of sperm offer good opportunities to study the potential genetic benefits that females can obtain from polyandry. Here, we report the results of a study examining the relationships between polyandry and components of female fitness in the common lizard (Lacerta vivipara). We found that polyandrous females produce larger clutches than monandrous females. Polyandrous females also lose fewer offspring during the later stages of gestation and at birth, but we did not find any relationship between polyandry and physical characteristics of viable neonates. Our results were consistent with the predictions of the intrinsic male quality hypothesis, while inbreeding avoidance and genetic incompatibility avoidance might also explain some part of the variation observed in clutch size. Moreover, the benefits of polyandry appeared to depend on female characteristics, as revealed by an interaction between reproductive strategy and female length on reproductive success. Thus, all females did not benefit equally from mating with multiple males, which could explain why polyandry and monandry coexist.

Prior classical olfactory conditioning improves odour-cued flight orientation of honey bees in a wind tunnel.

Odours are key cues used by the honey bee in various situations. They play an important role in sexual attraction, social behaviour and location of profitable food sources. Here, we were interested in the role of odours in orientation at short distance, for instance the approach flight to a floral patch or in close proximity to the hive entrance. Using a newly designed wind tunnel, we investigated the orientation behaviour of the bee towards two different odours: a social odour and a floral component, linalool. We then tested the effect of prior olfactory conditioning (conditioning of the proboscis extension reflex) on subsequent flight orientation. We showed that both stimuli induced orientated behaviour (orientated flights, circling around the odour source) in up to 70% of the worker bees, social odour being slightly more attractive than the linalool. We found thereafter that orientation performance towards the floral compound can be significantly enhanced by prior classical olfactory learning. This type of information transfer, from a Pavlovian associative context to an orientation task, might allow future foragers to acquire, within the hive, relevant information about the odours and food they will encounter during their later foraging bouts.