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Archaux F.,IRSTEA | Henry P.-Y.,CNRS Mechanical Adaptation and Evolution | Gimenez O.,CNRS Center of Evolutionary and Functional Ecology
Methods in Ecology and Evolution | Year: 2012

Numbers of individuals or species are often recorded to test for variations in abundance or richness between treatments, habitat types, ecosystem management types, experimental treatments, time periods, etc. However, a difference in mean detectability among treatments is likely to lead to the erroneous conclusion that mean abundance differs among treatments. No guidelines exist to determine the maximum acceptable difference in detectability. In this study, we simulated count data with imperfect detectability for two treatments with identical mean abundance (N) and number of plots (nplots) but different mean detectability (p). We then estimated the risk of erroneously concluding that N differed between treatments because the difference in p was ignored. The magnitude of the risk depended on p, N and nplots. Our simulations showed that even small differences in p can dramatically increase this risk. A detectability difference as small as 4-8% can lead to a 50-90% risk of erroneously concluding that a significant difference in N exists among treatments with identical N=50 and nplots=50. Yet, differences in p of this magnitude among treatments or along gradients are commonplace in ecological studies. Fortunately, simple methods of accounting for imperfect detectability prove effective at removing detectability difference between treatments. Considering the high sensitivity of statistical tests to detectability differences among treatments, we conclude that accounting for detectability by setting up a replicated design, applied to at least part of the design scheme and analysing data with appropriate statistical tools, is always worthwhile when comparing count data (abundance, richness). © 2011 The Authors. Methods in Ecology and Evolution © 2011 British Ecological Society.


Coulon A.,Cornell University | Coulon A.,CNRS Mechanical Adaptation and Evolution
Molecular Ecology Resources | Year: 2010

Genhet is an R function which calculates the five most used estimates of individual heterozygosity. The advantage of this program is that it can be applied to any diploid genotype dataset, without any limitation in the number of individuals, loci or alleles. Its detailed manual should allow people who have never used R before to make the function work quite easily. The program is freely available at http://www.aureliecoulon.net/research/ac-computer-programs. html. © 2009 Blackwell Publishing Ltd.


Herrel A.,CNRS Mechanical Adaptation and Evolution | Bonneaud C.,French National Center for Scientific Research
Journal of Experimental Biology | Year: 2012

Amphibians are ideal taxa with which to investigate the effects of climate change on physiology, dispersal capacity and distributional ranges as their physiological performance and fitness is highly dependent on temperature. Moreover, amphibians are among the most endangered vertebrate taxa. Here we use the tropical clawed frog, Xenopus tropicalis, as a model system to explore effects of temperature on locomotor performance. Our analyses show that locomotion is thermally sensitive, as illustrated by significant effects of temperature on terrestrial exertion capacity (time until exhaustion) and aquatic burst speed (maximal burst swimming velocity and maximal burst swimming acceleration capacity). Exertion performance measures had relatively lower temperature optima and narrower performance breadth ranges than measures of burst speed. The narrow 80% performance breadths confirm predictions that animals from stable environments should display high thermal sensitivity and, combined with the divergent temperature optima for exertion capacity and burst speed, underscore the vulnerability of tropical species such as X. tropicalis to even relatively small temperature changes. The temperature sensitivity of locomotor performance traits in X. tropicalis suggests that tropical ectotherms may be impacted by predicted changes in climate. © 2012. Published by The Company of Biologists Ltd.


Stevens V.M.,CNRS Mechanical Adaptation and Evolution | Stevens V.M.,University of Liège | Turlure C.,CNRS Mechanical Adaptation and Evolution | Baguette M.,CNRS Mechanical Adaptation and Evolution
Biological Reviews | Year: 2010

Dispersal has recently gained much attention because of its crucial role in the conservation and evolution of species facing major environmental changes such as habitat loss and fragmentation, climate change, and their interactions. Butterflies have long been recognized as ideal model systems for the study of dispersal and a huge amount of data on their ability to disperse has been collected under various conditions. However, no single 'best' method seems to exist leading to the co-occurrence of various approaches to study butterfly mobility, and therefore a high heterogeneity among data on dispersal across this group. Accordingly, we here reviewed the knowledge accumulated on dispersal and mobility in butterflies, to detect general patterns. This meta-analysis specifically addressed two questions. Firstly, do the various methods provide a congruent picture of how dispersal ability is distributed across species? Secondly, is dispersal species-specific? Five sources of data were analysed: multisite mark-recapture experiments, genetic studies, experimental assessments, expert opinions, and transect surveys. We accounted for potential biases due to variation in genetic markers, sample sizes, spatial scales or the level of habitat fragmentation. We showed that the various dispersal estimates generally converged, and that the relative dispersal ability of species could reliably be predicted from their relative vagrancy (records of butterflies outside their normal habitat). Expert opinions gave much less reliable estimates of realized dispersal but instead reflected migration propensity of butterflies. Within-species comparisons showed that genetic estimates were relatively invariable, while other dispersal estimates were highly variable. This latter point questions dispersal as a species-specific, invariant trait. © 2010 Cambridge Philosophical Society.


Vuarin P.,CNRS Mechanical Adaptation and Evolution | Dammhahn M.,Leibniz Institute for Primate Research | Henry P.-Y.,CNRS Mechanical Adaptation and Evolution
Functional Ecology | Year: 2013

Phenotypic flexibility is a major mechanism in compensating climate-driven changes in resource availability. Heterotherms can use daily torpor to overcome resource shortages and adverse environmental conditions. The expression of this adaptive energy-saving strategy varies among individuals, but the factors constraining individual flexibility remain largely unknown. As energy availability depends on individual stores and/or on the ability to acquire food, the propensity and flexibility in torpor use are expected to be constrained by body condition and/or size, respectively. The aim of this study was to test whether the dependency of torpor depth on air temperature was constrained by body condition and/or body size in a small heterothermic primate, the grey mouse lemur (Microcebus murinus). During the onset of the dry season, we monitored air temperature as well as skin temperatures of 14 free-ranging individuals (12 females, two males) of known body mass and size. Unexpectedly, torpor depth depended as much on air temperature as on body condition and size. Fatter, or larger, mouse lemurs underwent deeper torpor than smaller, or leaner, ones. Individual reaction norms of torpor depth to air temperature also revealed that the propensity to undergo deep torpor and the flexibility in torpor depth were enhanced by large body size and high body condition, whereas small, lean individuals remained normothermic. Our study illustrates that alternative physiological strategies to overcome temperature constraints co-occur in a population, with body size and condition being key determinants of the energy conservation strategy that an individual can launch. © 2013 The Authors. Functional Ecology © 2013 British Ecological Society.


Canale C.I.,CNRS Mechanical Adaptation and Evolution | Henry P.-Y.,CNRS Mechanical Adaptation and Evolution
Functional Ecology | Year: 2011

Resource-limiting conditions impose a change in the energetic distribution between competing physiological processes. Over the past decade there has been increasing interest in trade-offs between the immune system and competing energy-consuming life-history traits. However, the trade-offs with energy saving mechanisms, such as heterothermy, have received limited attention. The goal of this study is to determine how daily heterothermy expression could be adjusted to counterbalance the energetic requirements for the activation of the immune system depending on food availability (ad libitum vs. 40% calorie restriction) in a heterothermic primate, the Grey Mouse Lemur (Microcebus murinus). On the day of the immune challenge, torpor was removed through the onset of fever, inducing a thermogenic cost. On the days following, food-restricted individuals returned to deep torpor (i.e. energy saving) whereas those fed ad libitum continued to skip torpor for at least three additional days. The rapid return to an energy saving state in food restricted individuals raises new questions on the relationship between body temperature and immunocompetence. We suggest that (i) hyperthermia provides the first line of defence against pathogens, which is a trait common to all organisms, (ii) but that hypothermia may also protect the host by inhibiting pathogen proliferation. © 2010 The Authors. Functional Ecology © 2010 British Ecological Society.


Canale C.I.,CNRS Mechanical Adaptation and Evolution | Henry P.-Y.,CNRS Mechanical Adaptation and Evolution
Climate Research | Year: 2010

As ecosystems undergo global changes, there is increasing interest in understanding how organisms respond to changing environments. Recent evidence drawn from available vertebrate studies suggests that most of the phenotypic responses to climate change would be due to plasticity. We hypothesize that organisms that have evolved in unpredictable environments inform us about the mechanisms of phenotypic plasticity which provide an adaptive response to climate instability. As climate changes increase climatic hazards, these resilience mechanisms are expected to spread within species, populations and communities. We review studies that have demonstrated the importance of phenotypic plasticity in different life-history traits in overcoming climate uncertainty. We focus on organisms from unstable, recurrently energetically restrictive environments which possess a variety of morphological, physiological and/or behavioural adaptations to climate-driven selective pressures. First, we treat plastic morphological changes in response to fluctuating food availability. Adjustment of morphometric traits and/or organ size to energy supply would be essential in harsh environments. Second, we review the role of flexible energy-saving mechanisms, such as daily torpor, hibernation and energy storage, in overcoming climate-driven energetic shortages. Lastly, we address the role of plastic modulation of reproduction in fine-tuning the energy allocation to offspring production according to environmental conditions, with an emphasis on opportunistic breeding. Overall, we predict that species (or genotypes) possessing these efficient physiological mechanisms of resilience to unpredictable water and food fluctuations will be selectively advantaged in the face of increasing climatic instability. © Inter-Research 2010.


Ponge J.-F.,CNRS Mechanical Adaptation and Evolution
Ecology and Evolution | Year: 2013

The present text exposes a theory of the role of disturbances in the assemblage and evolution of species within ecosystems, based principally, but not exclusively, on terrestrial ecosystems. Two groups of organisms, doted of contrasted strategies when faced with environmental disturbances, are presented, based on the classical r-K dichotomy, but enriched with more modern concepts from community and evolutionary ecology. Both groups participate in the assembly of known animal, plant, and microbial communities, but with different requirements about environmental fluctuations. The so-called "civilized" organisms are doted with efficient anticipatory mechanisms, allowing them to optimize from an energetic point of view their performances in a predictable environment (stable or fluctuating cyclically at the scale of life expectancy), and they developed advanced specializations in the course of evolutionary time. On the opposite side, the so-called "barbarians" are weakly efficient in a stable environment because they waste energy for foraging, growth, and reproduction, but they are well adapted to unpredictably changing conditions, in particular during major ecological crises. Both groups of organisms succeed or alternate each other in the course of spontaneous or geared successional processes, as well as in the course of evolution. The balance of "barbarians" against "civilized" strategies within communities is predicted to shift in favor of the first type under present-day anthropic pressure, exemplified among others by climate warming, land use change, pollution, and biological invasions. © 2013 The Authors. Ecology and Evolution.


Ponge J.-F.,CNRS Mechanical Adaptation and Evolution
Soil Biology and Biochemistry | Year: 2013

The present review was undertaken to add more information on the place taken by humus forms in plant-soil interactions. Three questions were asked: (i) are humus forms under the control of plant-soil relationships, (ii) are humus forms the main seat of these relationships, and (iii) can humus forms explain interactions between aboveground and belowground biodiversity. Some conflicting views about humped-back models of species richness may be resolved by considering a limited number of stable humus forms (here considered as ecosystem strategies) which should be treated separately rather than in a single model. Mull, moder and mor pathways are each characterized by a fine tuning between aboveground and belowground communities, the humus form (including litter) being the place where resonance between these communities takes place, both in functional and evolutionary sense. © 2012 Elsevier Ltd.


Marchal J.,CNRS Mechanical Adaptation and Evolution | Pifferi F.,CNRS Mechanical Adaptation and Evolution | Aujard F.,CNRS Mechanical Adaptation and Evolution
Annals of the New York Academy of Sciences | Year: 2013

Through its antioxidant, anticarcinogenic, and anti-inflammatory properties, resveratrol has become a candidate for drug development in the context of aging studies. Scientific evidence has highlighted its potential as a therapeutic agent for cardiovascular diseases and some cancers but also as an antiaging molecule. Resveratrol is thought to mimic the beneficial effects of chronic and moderate calorie restriction. Nevertheless, no study has demonstrated the prolongation of life span in healthy nonobese mammal models. This review summarizes recent findings on the effects of resveratrol on aging and life span in mammals. In our opinion, more studies should be performed to assess the effects of a chronic dietary intake of resveratrol in long-lived species close to humans, such as nonhuman primates. This will certainly generate more evidence about the ability of resveratrol to achieve the physiological benefits that have been observed in small mammal laboratory models and feature the eventual unwanted secondary effects that may occur under high levels of resveratrol. © 2013 New York Academy of Sciences.

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