French birds lag behind climate warming

Biodiversity responses to climate warming have been documented through the study of changes in distributions, abundances or phenologies of individual species or in more integrated measures such as species community richness and composition. However, whether these observed population and community changes are occurring fast enough to cope with new climatic conditions remain uncertain and hardly quantifiable. Here, using spatial and temporal trends from the French breeding bird survey, we show that although bird assemblages are strongly responding to climate warming, this response is slower than expected for catching up with the current temperature increase. During the last two decades, French birds have only achieved 54% of the response required to follow temperature increase, and have accumulated, in 18 years, a 97 km delay in their northward shift. We thus developed a framework to measure both the observed and predicted response of species assemblage to climate change, an approach which is flexible enough to be applicable to any taxa with large-scale survey data, using either abundance or distribution data. For example, it can be further used to test if different delays are found across groups or if, for a given group, the delay depends on the land-use contexts

Familial versus mass selection in small populations

We used diffusion approximations and a Markov-chain approach to investigate the consequences of familial selection on the viability of small populations both in the short and in the long term. The outcome of familial selection was compared to the case of a random mating population under mass selection. In small populations, the higher effective size, associated with familial selection, resulted in higher fitness for slightly deleterious and/or highly recessive alleles. Conversely, because familial selection leads to a lower rate of directional selection, a lower fitness was observed for more detrimental genes that are not highly recessive, and with high population sizes. However, in the long term, genetic load was almost identical for both mass and familial selection for populations of up to 200 individuals. In terms of mean time to extinction, familial selection did not have any negative effect at least for small populations (N ≤ 50). Overall, familial selection could be proposed for use in management programs of small populations since it increases genetic variability and short-term viability without impairing the overall persistence times

On the expected relationship between inbreeding, fitness, and extinction

We assessed the expected relationship between the level and the cost of inbreeding, measured either in terms of fitness, inbreeding depression or probability of extinction. First, we show that the assumption of frequent, slightly deleterious mutations do agree with observations and experiments, on the contrary to the assumption of few, moderately deleterious mutations. For the same inbreeding coefficient, populations can greatly differ in fitness according to the following: (i) population size; larger populations show higher fitness (ii) the history of population size; in a population that recovers after a bottleneck, higher inbreeding can lead to higher fitness and (iii) population demography; population growth rate and carrying capacity determine the relationship between inbreeding and extinction. With regards to the relationship between inbreeding depression and inbreeding coefficient, the population size that minimizes inbreeding depression depends on the level of inbreeding: inbreeding depression can even decrease when population size increases. It is therefore clear that to infer the costs of inbreeding, one must know both the history of inbreeding (e.g. past bottlenecks) and population demography

Interactions entre biodiversité et sécurité alimentaire

Chapitre de l’ouvrage collectif Penser une démocratie alimentaire Volume II – Proposition Lascaux entre ressources naturelles et besoins fondamentaux, F. Collart Dutilleul et T. Bréger (dir), Inida, San José, 2014, pp. 375-383International audienceLa biodiversité désigne la diversité biologique du vivant (faune, flore, micro-organismes) à différents niveaux d’organisation écologique. Déclinée en diversité spécifique, génétique et écosystémique, elle englobe sa composition, sa structure et ses fonctions. Un enjeu est de maintenir ces propriétés, les capacités évolutives du vivant, d’adaptation face aux changements globaux. L’agriculture dépend de la biodiversité, du bon fonctionnement des écosystèmes, à travers la diversité biologique nécessaire à la domestication, la fertilité des sols ou la pollinisation. En conséquence, le devenir de la biodiversité et de l’agriculture sont liés. Cet article présente les concepts majeurs permettant de formaliser et comprendre leurs interactions, donc leurs dynamiques, présentes et futures

Relationship between biodiversity and agricultural production

International audienceThe intensification of agriculture is one of the main causes of biodiversity loss. We model the interdependent relationship between agriculture and wild biodiversity providing regulating services to agriculture on farmed land. We suppose that while agriculture has a negative impact on wild biodiversity, the latter can increase agricultural production. Farmers act as myopic agents, who maximize their instantaneous profit without considering the negative effects of their practice on the evolution of biodiversity. Two unexpected results arise (a) a tax on inputs can have a positive effect on yield since it can be considered as a social signal helping farmers to avoid myopic behavior concerning the positive effect of biodiversity on yield; (b) increasing biodiversity productivity, a proposal of ecological intensification, affects negatively the level of biodiversity, a counter‐intuitive result; due to the fact that when biodiversity is more productive, farmers can maintain lower biodiversity to get the same yield

The hierarchical island model revisited

Formulae were derived for the genetic differentiation between populations within a metapopulation (FSM), and between metapopulations (FMT) as functions of migration and mutation rates, size and number of populations and metapopulations. We show that FMT = 1/(1 + 4Nem), where Ne is the effective size of a metapopulation, and where the migration rate between metapopulations is m. The formulae for FMT and FSM were more general than previously proposed since we have relaxed some previously made hypotheses and we included the effect of the mutation rate. Using our formula, some unexpected result of estimation of gene flow, previously obtained, can be explained readily