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Plasticity in breeding phenology is not consistent across populations
Puy Mary population
Recent studies have identified so-called universal ecological consequences of climate warming, especially an advanced breeding and non-breeding phenology in many populations of plants and animals. In seasonal environments, among species variation in the extent of plasticity of phenology can generate temporal mistmatch between trophic level, where for example predators have higher energetic demands when preys are scarce in the environment. Until recently, however, we knew little about intra-specific variation in breeding phenology, which may vary across populations due to differences in selection or constraints. In a recent study, we combined data from more than 10 years of detailed monitoring of the breeding phenology in 11 populations of common lizards across the Massif Central. Our data demonstrate unambiguously that breeding phenology responds more to climate warming in some populations than in others. Contrary to some predictions from evolutionary theory, plasticity was stronger in warmer and less variable climates.
Picture: The Puy Mary population is characterised by cold and less variable climate conditions during gestation. This population is predicted to exhibit flat plasticity of the breeding phenology. Photograph: J.-F. Le Galliard.
Last Updated ( vendredi, 26 février 2016 )
Ecosystem service provision: new perspectives from network theory
Quintessence: ecological network figure
The ecosystem services (EcoS) concept is being used increasingly to attach values to natural systems and the multiple benefits they provide to human societies. Ecosystem processes or functions only become EcoS if they are shown to have social and/or economic value. This should assure an explicit connection between the natural and social sciences, but EcoS approaches have been criticized for retaining little natural science. Preserving the natural, ecological science context within EcoS research is challenging because the multiple disciplines involved have very different traditions and vocabularies (common-language challenge) and span many organizational levels and temporal and spatial scales (scale challenge) that define the relevant interacting entities (interaction challenge). We propose a network-based approach to transcend these discipline challenges and place the natural science context at the heart of EcoS research.
Bohan, D. and the QUINTESSENCE consortium. 2016. Networking our way to better Ecossystem Service provision. Trends in Ecology and Evolution 31(2):105-115.
Last Updated ( vendredi, 26 février 2016 )
What maintains variation in personality traits?
Consistent individual differences in behaviours such as exploration, aggressiveness, social tolerance, risk taking and social learning are seen in numerous animal species. The maintenance of consistent individual differences (also called temperaments) and the evolution of correlation among behavioural traits (also called behavioural syndromes) have therefore become the subjects of intense research. Recent evolutionary models indicate that heterogeneity of natural selection on temperaments, correlational selection on behavioural traits and life history trade-offs are crucial to the evolution of consistent behavioural types and of behavioural syndromes. However, in a recent review on the subject, Dingenmanse and Wolf (Phil Trans Roy Soc 2010) pointed out that " the time has come for empiricists to start testing the assumptions and predictions derived from adaptive models presented in the literature more explicitly". Indeed, after almost a decade of research effort on behavioural syndromes, we still know too little about the micro-evolutionary processes responsible for their maintenance.
In a study published recently in Journal of Evolutionary Biology, we present for the first time data about multivariate selection on distinct behavioural traits (activity, boldness and sociability) in semi-natural populations of lizards ranging from low to high densities. Our study is unique because we investigated the strength and shape of natural selection on behavioural syndromes in a large birth cohort of lizards. In addition, we manipulated population density to draw causal inferences about the effects of environmental conditions on natural selection. We found that natural selection on behavioural temperaments of juvenile common lizards was heterogeneous between density treatments and fitness traits. Yet, observed patterns were also more complex than anticipated by life history theory because consistency of individual differences in behaviours across time was weak and behaviours were not involved in a life history trade-off between production and survival. Correlational selection on behavioural traits was weak in average. A significant negative correlational selection on activity and boldness existed for body growth irrespective of population density, which runs opposite to the emergent behavioural syndrome linking high activity with bolder behaviour. These major findings confirm that heterogeneous selection rather than life history trade-offs plays an important role in the maintenance of individual differences in exploration-activity and sociability because the fitness outcomes of a behavioural strategy depends on variation in population density. Future models for adaptive personality differences should therefore include density-dependent selection in order to gain a better understanding of the ecological conditions most likely to favour the evolution of animal personality variation.
Last Updated ( mardi, 18 août 2015 )
The UV reflective throat of male common lizards plays the role of a badge of status
According to the badge of status hypothesis, adult males of many vertebrate species exhibit, perceive and use ultraviolet (UV) colouration during aggressive interactions to settle territorial conflicts. Previous experimental studies of this question included protocols that cancel UV reflectance well below natural variability and can seldom be used to draw conclusions about inter-individual variability. In addition, they often did not test for important factors known to influence aggressive interactions, and none have controlled for effects of resident-intruder status. In addition, mechanisms ensuring the honesty of UV signals are hotly debated today because strong evidences of condition-dependent UV signals are still too rare. In this study, we investigated for the first time if UV signals interact with prior residency and familiarity to influence conflict resolution among males during the mating season. We used an experimental protocol where we decreased UV reflectance within its natural range in adult male common lizards (Zootoca vivipara). Males of this species display a bright UV colour patch on their throat that they expose to conspecifics during behavioural conflicts. We measured reflectance of wild males and quantified behavioural interactions during repeated resident-intruder encounters where UV reflectance was alternatively reduced or not in both rivals in a full factorial design. We further asked whether UV throat reflectance correlates with morphology, physiology and blood parasite load to distinguish between conventional and condition-dependent signalling. Our results show that UV manipulation predicts contest outcomes and aggressive behaviours when opponents are not familiar. Moreover, we demonstrate for the first time that effects of UV manipulation persist when opponents are familiar. However, we found no evidence supporting the hypothesis of condition-dependence of the expression of UV colours. Altogether, this suggests that UV reflectance acts as an arbitrary or conventional signal, which mediates the outcome of male-male competition in common lizards.
Digital visible (top) and UV (bottom) black-and-white photographs of a common lizard male (left) and female (right) - (c) Mélissa Martin, CNRS
 Digital photograph of lizard
Last Updated ( lundi, 09 novembre 2015 )