There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation.

Summary1. There is growing evidence that dispersal is highly phenotypically plastic, i.e. that dispersal is condition-dependent. In the common lizard, dispersal has even been shown to be in¯uenced by the maternal environment during pregnancy. Juveniles in good condition or issued from mothers in good condition disperse earlier or in higher numbers. 2. We hypothesized that plasma corticosterone was the proximate mechanism by which condition and dispersal are linked, and tested this by manipulating the level of circulating corticosterone in pregnant females of the common lizard. 3. After parturition, we measured juvenile attractiveness towards the mother and juvenile dispersal of corticosterone (B) and placebo (P) implanted females. 4. Ospring of B females did disperse in lower number than those of P females. B ospring were also more attracted by the mother's odour than P ospring. 5. In quite a few cases, the behavioural response of juveniles was dependent on the interaction between the hormonal treatment and the mother snout±vent length or condition (body weight corrected for snout±vent length). 6. Corticosterone constitutes therefore one of the proximate mechanisms involved in the prenatal control of juvenile dispersal in this species. Along with other results, it is proposed that prenatal control of dispersal has evolved in order to avoid competition between mothers and their ospring.

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Summary 1.Integrative studies on ageing patterns in multiple traits of organisms are challenging and rare in free-living populations. However, developing integrative approaches could prove useful to understanding ageing patterns as causes of age variations are diverse, with conflicting or related actions. Accordingly, we investigated age variation of multiple aspects in the common lizard Lacerta (Zootoca) vivipara. 2. In a wild population of common lizards, we studied five fitness components, three physiological traits (cell-mediated immunity, corticosterone level, resting metabolic rate), and controlled for individual and environmental heterogeneities. To quantify ageing patterns in fitness, we used individual-based data collected over 14 years (18 684 captures, 892 reproductive events). 3. Ageing patterns were found in multiple aspects. They provided evidence for female maturation early in adulthood (access to reproduction, litter size), followed by senescence in female reproduction (litter success) and survival. In parallel to senescence, a pattern of terminal investment enhanced offspring quality (offspring body size, offspring corpulence, litter success). Ageing patterns involved physiology with higher metabolic rate and T cell-mediated immune response in old females. 4. Several ageing patterns were dependent on environmental and individual characteristics (habitat, year, sex, body size). Interestingly, senescence occurred only in females with a high reproductive effort early in life. Rarely showed, this trade-off between early and late-life performances is expected under the antagonistic pleiotropy and disposable soma theories of senescence. 5. Overall, this study emphasizes the interest of integrative studies to investigate the multifaceted process of ageing.

Under chronic stress, carotenoid-based colouration has often been shown to fade. However, the ecological and physiological mechanisms that govern colouration still remain largely unknown. Colour changes may be directly induced by the stressor (for example through reduced carotenoid intake) or due to the activation of the physiological stress response (PSR, e.g. due to increased blood corticosterone concentrations). Here, we tested whether blood corticosterone concentration affected carotenoid-based colouration, and whether a trade-off between colouration and PSR existed. Using the common lizard (Lacerta vivipara), we correlatively and experimentally showed that elevated blood corticosterone levels are associated with increased redness of the lizard's belly. In this study, the effects of corticosterone did not depend on carotenoid ingestion, indicating the absence of a trade-off between colouration and PSR for carotenoids. While carotenoid ingestion increased blood carotenoid concentration, colouration was not modified. This suggests that carotenoid-based colouration of common lizards is not severely limited by dietary carotenoid intake. Together with earlier studies, these findings suggest that the common lizard's carotenoid-based colouration may be a composite trait, consisting of fixed (e.g. genetic) and environmentally elements, the latter reflecting the lizard's PSR.

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A challenge to ecologists and evolutionary biologists is predicting organismal responses to the anticipated changes to global ecosystems through climate change. Most evidence suggests that short-term global change may involve increasing occurrences of extreme events, therefore the immediate response of individuals will be determined by physiological capacities and life-history adaptations to cope with extreme environmental conditions. Here, we consider the role of hormones and maternal effects in determining the persistence of species in altered environments. Hormones, specifically steroids, are critical for patterning the behaviour and morphology of parents and their offspring. Hence, steroids have a pervasive influence on multiple aspects of the offspring phenotype over its lifespan. Stress hormones, e.g. glucocorticoids, modulate and perturb phenotypes both early in development and later into adulthood. Females exposed to abiotic stressors during reproduction may alter the phenotypes by manipulation of hormones to the embryos. Thus, hormone-mediated maternal effects, which generate phenotypic plasticity, may be one avenue for coping with global change. Variation in exposure to hormones during development influences both the propensity to disperse, which alters metapopulation dynamics, and population dynamics, by affecting either recruitment to the population or subsequent life-history characteristics of the offspring. We suggest that hormones may be an informative index to the potential for populations to adapt to changing environments.

Corticosterone is an important hormone of the stress response that regulates physiological processes and modifies animal behavior. While it positively acts on locomotor activity, it may negatively affect reproduction and social activity. This suggests that corticosterone may promote behaviors that increase survival at the cost of reproduction. In this study, we experimentally investigate the link between corticosterone levels and survival in adult common lizards (Lacerta vivipara) by comparing corticosterone-treated with placebo-treated lizards. We experimentally show that corticosterone enhances energy expenditure, daily activity, food intake, and it modifies the behavioral time budget. Enhanced appetite of corticosterone-treated individuals compensated for increased energy expenditure and corticosterone-treated males showed increased survival. This suggests that corticosterone may promote behaviors that reduce stress and it shows that corticosterone per se does not reduce but directly or indirectly increases longer-term survival. This suggests that the production of corticosterone as a response to a stressor may be an adaptive mechanism that even controls survival.