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Mouquet N.,Montpellier University | Gravel D.,University of Quebec at Rimouski | Massol F.,IRSTEA | Massol F.,CNRS Center of Evolutionary and Functional Ecology | Calcagno V.,CNRS Sophia Agrobiotech Institute
Ecology Letters | Year: 2013

Keystone species are defined as having disproportionate importance in their community. This concept has proved useful and is now often used in conservation ecology. Here, we introduce the concept of keystone communities (and ecosystems) within metacommunities (and metaecosystems). We define keystone and burden communities as communities with impacts disproportionately large (positive or negative respectively) relative to their weight in the metacommunity. We show how a simple metric, based on the effects of single-community removals, can characterise communities along a 'keystoneness' axis. We illustrate the usefulness of this approach with examples from two different theoretical models. We further distinguish environmental heterogeneity from species trait heterogeneity as determinants of keystoneness. We suggest that the concept of keystone communities/ecosystems will be highly beneficial, not only as a fundamental step towards understanding species interactions in a spatial context, but also as a tool for the management of disturbed landscapes. © 2012 Blackwell Publishing Ltd/CNRS. Source


Giordanengo P.,University of Picardie Jules Verne | Giordanengo P.,CNRS Sophia Agrobiotech Institute
Arthropod-Plant Interactions | Year: 2014

Electrical penetration graph (EPG) technique is a powerful tool to investigate the hidden feeding behavior of piercing-sucking insects allowing to link recorded EPG waveforms to stylet penetration and complex behaviors related to feeding activities occurring within plant tissue. Calculating the numerous EPG parameters necessary to unravel the complex insect-plant interactions is very time consuming, and few tools have been developed to automate it. EPG-Calc is a rich internet application intended to fill this gap, providing a fast and user-friendly web-based interface that uses analysis files from dedicated software (STYLET+) or database-compatible CSV text files containing waveform codes and cumulative time as input, and produces output files in database-compatible CSV text or Microsoft Excel® XLS format that are directly usable by different statistical analysis softwares. EPG-Calc greatly reduces the time needed for EPG parameters calculation and allows to calculate more than 100 different parameters based on standardized definitions and calculus methods in such a way that avoid confusion between all kinds of definitions and calculations by individual authors. © 2014 Springer Science+Business Media Dordrecht. Source


Feyereisen R.,CNRS Sophia Agrobiotech Institute
Pest Management Science | Year: 2015

P450 enzymes are encoded by a large number of genes in insects, often over a hundred. They play important roles in insecticide metabolism and resistance, and growing numbers of P450 enzymes are now known to catalyse important physiological reactions, such as hormone metabolism or cuticular hydrocarbon synthesis. Ways to inhibit P450 enzymes specifically or less specifically are well understood, as P450 inhibitors are found as drugs, as fungicides, as plant growth regulators and as insecticide synergists. Yet there are no P450 inhibitors as insecticides on the market. As new modes of action are constantly needed to support insecticide resistance management, P450 inhibitors should be considered because of their high potential for insect selectivity, their well-known mechanisms of action and the increasing ease of rational design and testing. © 2014 Society of Chemical Industry. Source


Fauvergue X.,French National Institute for Agricultural Research | Fauvergue X.,University of Nice Sophia Antipolis | Fauvergue X.,CNRS Sophia Agrobiotech Institute
Entomologia Experimentalis et Applicata | Year: 2013

Like other animals and plants, insects may find it difficult to survive and reproduce in small populations, to the extent that their long-term persistence may be jeopardized. The Allee effect is a theoretical framework that formalizes this decrease in survival or reproduction in small populations, and the resulting decrease in population growth and persistence. Mating failure in low-density populations is likely to generate an Allee effect and, therefore, has a major effect on the functioning of small populations. Here, I review mate-finding Allee effects in insect species, and their consequences for individual mating success, population dynamics, and population management. I focus, in particular, on the comparison of theoretical expectations with observational data. Several studies have reported some degree of mating failure at low density. However, almost none of the datasets available allow comparison with the predictions of classical mate-searching models. A few studies at the population level have reported the co-occurrence of mating failure at low density and a demographic Allee effect, but no study has yet clearly demonstrated a causal relationship between mating failure and lower rates of population growth. Thus, although the theoretical development of management tactics based on Allee effects is considered promising, the current lack of evidence supporting this strategy limits its potential relevance. I call here for a more rigorous approach to the study of mate-finding Allee effects and propose new approaches for this purpose. © 2012 The Netherlands Entomological Society. Source


Castagnone-Sereno P.,CNRS Sophia Agrobiotech Institute | Danchin E.G.J.,CNRS Sophia Agrobiotech Institute
Journal of Evolutionary Biology | Year: 2014

Asexual reproduction is usually considered as an evolutionary dead end, and difficulties for asexual lineages to adapt to a fluctuating environment are anticipated due to the lack of sufficient genetic plasticity. Yet, unlike their sexual congeners, mitotic parthenogenetic root-knot nematode species, Meloidogyne spp., are remarkably widespread and polyphagous, with the ability to parasitize most flowering plants. Although this may reflect in part the short-term stability of agricultural environments, the extreme parasitic success of these clonal species points them as an outstanding evolutionary paradox regarding current theories on the benefits of sex. The discovery that most of the genome of the clonal species M. incognita is composed of pairs of homologous but divergent segments that have presumably been evolving independently in the absence of sexual recombination has shed new light on this evolutionary paradox. Together with recent studies on other biological systems, including the closely related sexual species M. hapla and the ancient asexual bdelloid rotifers, this observation suggests that functional innovation could emerge from such a peculiar genome architecture, which may in turn account for the extreme adaptive capacities of these asexual parasites. Additionally, the higher proportion of transposable elements in M. incognita compared to M. hapla and other nematodes may also be responsible in part for genome plasticity in the absence of sexual reproduction. We foresee that ongoing sequencing efforts should lead soon to a genomic framework involving genetically diverse Meloidogyne species with various different reproductive modes. This will undoubtedly promote the entire genus as a unique and valuable model system to help deciphering the evolution of asexual reproduction in eukaryotes. © 2014 European Society For Evolutionary Biology. Source

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