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Vignon M.,CNRS Host-Pathogen-Environment Interactions Laboratory | Vignon M.,French National Institute for Agricultural Research
Zoologica Scripta | Year: 2011

Taxonomists and evolutionary biologists frequently use a combination of morphological measurements to distinguish between species and investigate local adaptation. However, the entire set of characters often displays various degrees of collinearity. This paper discusses the effect of using collinear data in morphological taxonomy and ways to handle multicollinearity in a classification context, with special consideration for small sample size. In addition, I propose a robust and easy-to-use combination of dimension reduction using partial least squares (PLS) with traditional discriminant methods for morphological data. To do this, I investigated morphological variation patterns among four monogenean populations from the Pacific Ocean using the correlated morphological features of the sclerotized attachment organ. The new approach yielded better prediction results (lower classification error rates) than the traditional dimension reduction method based on principle component analysis (PCA) and is also much more robust for small sample size. This emphasizes that PLS may be more efficient than PCA in dealing with correlated data and extracting the most relevant morphological differences among groups. © 2011 The Author. Zoologica Scripta © 2011 The Norwegian Academy of Science and Letters. Source

Ayata S.D.,University Pierre and Marie Curie | Ayata S.D.,French National Center for Scientific Research | Huret M.,Center Ifremer Of Nantes | Irisson J.O.,CNRS Host-Pathogen-Environment Interactions Laboratory
Progress in Oceanography | Year: 2010

Climate may act on the dispersal and connectivity of marine populations through changes in the oceanic circulation and temperature, and by modifying species' prey and predator distributions. As dispersal and connectivity remain difficult to assess in situ, a first step in studying the effects of climate change can be achieved using biophysical models. To date, only a few biophysical models have been used for this purpose. Here we review these studies and also include results from other recent modelling efforts. We show that increased sea temperature, a major change expected under climate warming, may impact dispersal and connectivity patterns via changes in reproductive phenology (e.g., shift in the spawning season), transport (e.g., reduced pelagic larval duration under faster development rates), mortality (e.g., changes in the exposure to lethal temperatures), and behaviour (e.g., increased larval swimming speed). Projected changes in circulation are also shown to have large effects on the simulated dispersal and connectivity patterns. Although these biophysical modelling studies are useful preliminary approaches to project the potential effects of climate change, we highlight their current limitations and discuss the way forward, in particular the need for adequate coupled hydrodynamic-biogeochemical simulations using atmospheric forcing from realistic climate change scenarios. © 2010 Elsevier Ltd. Source

Gourbiere S.,CNRS Host-Pathogen-Environment Interactions Laboratory | Gourbiere S.,University of Sussex | Dorn P.,Loyola University New Orleans | Tripet F.,Keele University | Dumonteil E.,Autonomous University of Yucatan
Heredity | Year: 2012

Triatomines are hemipteran bugs acting as vectors of the protozoan parasite Trypanosoma cruzi. This parasite causes Chagas disease, one of the major parasitic diseases in the Americas. Studies of triatomine genetics and evolution have been particularly useful in the design of rational vector control strategies, and are reviewed here. The phylogeography of several triatomine species is now slowly emerging, and the struggle to reconcile the phenotypic, phylogenetic, ecological and epidemiological species concepts makes for a very dynamic field. Population genetic studies using different markers indicate a wide range of population structures, depending on the triatomine species, ranging from highly fragmented to mobile, interbreeding populations. Triatomines transmit T. cruzi in the context of complex interactions between the insect vectors, their bacterial symbionts and the parasites; however, an integrated view of the significance of these interactions in triatomine biology, evolution and in disease transmission is still lacking. The development of novel genetic markers, together with the ongoing sequencing of the Rhodnius prolixus genome and more integrative studies, will provide key tools to expanding our understanding of these important insect vectors and allow the design of improved vector control strategies. © 2012 Macmillan Publishers Limited All rights reserved. Source

Theron A.,CNRS Host-Pathogen-Environment Interactions Laboratory
Advances in Parasitology | Year: 2015

One major challenge for parasites with complex cycles consists to succeed in the transmission from one host to the next host. To maximize the probability of encountering the right host, numerous trematode species have selected various emergence rhythms occurring during the escape of the short-lived cercariae from the mollusc host. Cercarial shedding patterns are beautiful examples of adaptation of the parasite for a successful rendezvous with its subsequent host. In this review, after an analysis of the technical and statistical aspects specific to such studies, we compile the knowledge and unresolved issues we have about the synchronization of these rhythms, their genetic support and the role of the host physiology or activity. We are also interested on how cercarial rhythmicity influences cercarial densities in waters of transmission sites and then the risk of host infection in case of schistosomiasis. Ecological significance of the inter- and intra-specific diversity of these rhythms is emphasized as well as the evolutionary implication of new chronotypes resulting from the capture of new host species and promoting reproductive isolation and alloxenic speciation. Currently, genome sequence data now available for some trematodes such as the schistosomes provide an unprecedented resource for new research approaches that should contribute identification of the genes and mechanisms involved in determining the cercarial shedding rhythms observed. © 2015 Elsevier Ltd. Source

Giraud T.,University Paris - Sud | Gourbiere S.,University of Sussex | Gourbiere S.,CNRS Host-Pathogen-Environment Interactions Laboratory | Gourbiere S.,French National Center for Scientific Research
Heredity | Year: 2012

Reproductive isolation is an essential ingredient of speciation, and much has been learned in recent years about the evolution of reproductive isolation and the genetics of reproductive barriers in animals and plants. Fungi have been neglected on these aspects, despite being tractable model eukaryotes. Here, we used a model fitting approach to look at the importance of different barriers to gene flow to explain the decrease of reproductive compatibility with genetic distance in fungi. We found support for the occurrence of reinforcement in the presyngamy compatibility among basidiomycetes. In contrast, no evidence for reinforcement was detected in ascomycetes, concurring with the idea that host/habitat adaptation in this group can pleiotropically cause reproductive isolation. We found no evidence of a snowballing accumulation of postsyngamic reproductive incompatibilities in either ascomycetes or the complex of anther smut fungi. Together with previous studies, our results suggest that ecologically based barriers to gene flow and karyotypic differences may have an important role in hybrid inviability and sterility in fungi. Interestingly, hybrid sterility appeared to evolve faster than hybrid inviability in fungi. © 2012 Macmillan Publishers Limited All rights reserved. © 2012 Macmillan Publishers Limited All rights reserved. Source

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