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.
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.
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.
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.
Castagnone-Sereno P.,CNRS Sophia Agrobiotech Institute |
Danchin E.G.J.,CNRS Sophia Agrobiotech Institute |
Perfus-Barbeoch L.,CNRS Sophia Agrobiotech Institute |
Abad P.,CNRS Sophia Agrobiotech Institute
Annual Review of Phytopathology | Year: 2013
Root-knot nematodes (RKNs) (Meloidogyne spp.) are obligate endoparasites of major worldwide economic importance. They exhibit a wide continuum of variation in their reproductive strategies, ranging from amphimixis to obligatory mitotic parthenogenesis. Molecular phylogenetic studies have highlighted divergence between mitotic and meiotic parthenogenetic RKN species and probable interspecific hybridization as critical steps in their speciation and diversification process. The recent completion of the genomes of two RKNs, Meloidogyne hapla and Meloidogyne incognita, that exhibit striking differences in their mode of reproduction (with and without sex, respectively), their geographic distribution, and their host range has opened the way for deciphering the evolutionary significance of (a)sexual reproduction in these parasites. Accumulating evidence suggests that whole-genome duplication (in M. incognita) and horizontal gene transfers (HGTs) represent major forces that have shaped the genome of current RKN species and may account for the extreme adaptive capacities and parasitic success of these nematodes. © Copyright ©2013 by Annual Reviews. All rights reserved.
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.
Puppo A.,CNRS Sophia Agrobiotech Institute |
Pauly N.,CNRS Sophia Agrobiotech Institute |
Boscari A.,CNRS Sophia Agrobiotech Institute |
Mandon K.,CNRS Sophia Agrobiotech Institute |
Brouquisse R.,CNRS Sophia Agrobiotech Institute
Antioxidants and Redox Signaling | Year: 2013
Significance: During the Legume-Rhizobium symbiosis, hydrogen peroxide (H2O2) and nitric oxide (NO) appear to play an important signaling role in the establishment and the functioning of this interaction. Modifications of the levels of these reactive species in both partners impair either the development of the nodules (new root organs formed on the interaction) or their N2-fixing activity. Recent Advances: NADPH oxidases (Noxs) have been recently described as major sources of H 2O2 production, via superoxide anion dismutation, during symbiosis. Nitrate reductases (NR) and electron transfer chains from both partners were found to significantly contribute to NO production in N 2-fixing nodules. Both S-sulfenylated and S-nitrosylated proteins have been detected during early interaction and in functioning nodules, linking reactive oxygen species (ROS)/NO production to redox-based protein regulation. NO was also found to play a metabolic role in nodule energy metabolism. Critical Issues: H2O2 may control the infection process and the subsequent bacterial differentiation into the symbiotic form. NO is required for an optimal establishment of symbiosis and appears to be a key player in nodule senescence. Future Directions: A challenging question is to define more precisely when and where reactive species are generated and to develop adapted tools to detect their production in vivo. To investigate the role of Noxs and NRs in the production of H2O2 and NO, respectively, the use of mutants under the control of organ-specific promoters will be of crucial interest. The balance between ROS and NO production appears to be a key point to understand the redox regulation of symbiosis. © Copyright 2013, Mary Ann Liebert, Inc.
Favery B.,CNRS Sophia Agrobiotech Institute |
Quentin M.,CNRS Sophia Agrobiotech Institute |
Jaubert-Possamai S.,CNRS Sophia Agrobiotech Institute |
Abad P.,CNRS Sophia Agrobiotech Institute
Journal of Insect Physiology | Year: 2016
Among plant-parasitic nematodes, the root-knot nematodes (RKNs) of the Meloidogyne spp. are the most economically important genus. RKN are root parasitic worms able to infect nearly all crop species and have a wide geographic distribution. During infection, RKNs establish and maintain an intimate relationship with the host plant. This includes the creation of a specialized nutritional structure composed of multinucleate and hypertrophied giant cells, which result from the redifferentiation of vascular root cells. Giant cells constitute the sole source of nutrients for the nematode and are essential for growth and reproduction. Hyperplasia of surrounding root cells leads to the formation of the gall or root-knot, an easily recognized symptom of plant infection by RKNs. Secreted effectors produced in nematode salivary glands and injected into plant cells through a specialized feeding structure called the stylet play a critical role in the formation of giant cells. Here, we describe the complex interactions between RKNs and their host plants. We highlight progress in understanding host plant responses, focusing on how RKNs manipulate key plant processes and functions, including cell cycle, defence, hormones, cellular scaffold, metabolism and transport. © 2015 Elsevier Ltd.
Quentin M.,CNRS Sophia Agrobiotech Institute |
Abad P.,CNRS Sophia Agrobiotech Institute |
Favery B.,CNRS Sophia Agrobiotech Institute
Frontiers in Plant Science | Year: 2013
Plant parasitic nematodes are microscopic worms, the most damaging species of which have adopted a sedentary lifestyle within their hosts. These obligate endoparasites have a biotrophic relationship with plants, in which they induce the differentiation of root cells into hypertrophied, multinucleate feeding cells (FCs). Effectors synthesized in the esophageal glands of the nematode are injected into the plant cells via the syringe-like stylet and play a key role in manipulating the host machinery. The establishment of specialized FCs requires these effectors to modulate many aspects of plant cell morphogenesis and physiology, including defense responses. This cell reprogramming requires changes to host nuclear processes. Some proteins encoded by parasitism genes target host nuclei. Several of these proteins were immunolocalized within FC nuclei or shown to interact with host nuclear proteins. Comparative genomics and functional analyses are gradually revealing the roles of nematode effectors. We describe here these effectors and their hypothesized roles in the unique feeding behavior of these pests. © 2013 Quentin, Abad and Favery.
Fauvergue X.,CNRS Sophia Agrobiotech Institute |
Vercken E.,CNRS Sophia Agrobiotech Institute |
Malausa T.,CNRS Sophia Agrobiotech Institute |
Hufbauer R.A.,Colorado State University
Evolutionary Applications | Year: 2012
Populations are introduced into novel environments in different contexts, one being the biological control of pests. Despite intense efforts, less than half introduced biological control agents establish. Among the possible approaches to improve biological control, one is to better understand the processes that underpin introductions and contribute to ecological and evolutionary success. In this perspective, we first review the demographic and genetic processes at play in small populations, be they stochastic or deterministic. We discuss the theoretical outcomes of these different processes with respect to individual fitness, population growth rate, and establishment probability. Predicted outcomes differ subtly in some cases, but enough so that the evaluating results of introductions have the potential to reveal which processes play important roles in introduced populations. Second, we attempt to link the theory we have discussed with empirical data from biological control introductions. A main result is that there are few available data, but we nonetheless report on an increasing number of well-designed, theory-driven, experimental approaches. Combining demography and genetics from both theoretical and empirical perspectives highlights novel and exciting avenues for research on the biology of small, introduced populations, and great potential for improving both our understanding and practice of biological control. © 2012 Blackwell Publishing Ltd.