Résumés soumis
Résumés soumis
Evolution of Sex Chromosomes: Using Comparative Methods to Study Traits That Do Not Fossilize
Symposium « Molecular Evolution/Évolution moléculaire »
Communication invitée
Chris Organ, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA. E-mail: organchris@gmail.com
Sex determination by chromosomal inheritance (genotypic sex determination) is common in amniotes and plays an important role in life history. Although sex chromosomes are often homomorphic, structural differences between homologous chromosomes is widespread. Inheritance of the heterogametic sex chromosome produces females (by inheriting the W; the ZW system) or males (by inheriting the Y; XY system). The ZW system is found in birds, snakes, and some other reptiles, while the XY system is found in mammals and some non-avian reptiles, like skinks. Generally, the heterogametic sex chromosome (W or Y) is smaller, heterochromatic, and gene poor in comparison to its partner. Although different information is genetically encoded in W versus Y chromosomes, their apparent degradation suggests a consistent general trend in the evolution of sex chromosomes. Theory suggests that heterogametic sex chromosomes decay rapidly, perhaps completely vanishing within 10 million years in some cases, through the accumulation of deleterious mutations in the non-recombining region. However, a comprehensive large scale, phylogenetically-grounded analysis of chromosomal degradation within amniotes has never been performed. Moreover, it is unknown how the phylogenetic decay rates differ between the XY and ZW systems. Here I present a large-scale phylogenetic analysis of XY and ZW sex chromosome evolution using a large catalogue of karyotypic measurements. I discuss the rates and first appearance of sex chromosomes in the dinosaur lineage and present a novel Bayesian comparative method to make phylogenetically-informed univariate predictions.
Analysis of the Evolution of the chordate proteome using the expert system DAGOBAH
Symposium « Molecular Evolution/Évolution moléculaire »
Communication invitée
Pierre Pontarotti UMR 7353 (AMU CNRS) Evolution Biologique et Modélisation , 3 place V. Hugo, case 19, 13003 Marseille, FRANCE. E-mail : Pierre.Pontarotti@univ-provence.fr
Species living today are the product of a long evolutionary history and the trace of this history is still present in their corresponding genomes.
The evolution of the genome occurs via changes that are fixed through the history of species. These changes take place during the duplication of the DNA and other events during meiosis and mitosis. These events give rise to substitutions, deletions, insertions and recombinations. Consequently, these modifications can have various impacts at different functional levels (by gene losses, pseudogenizations, duplications, domain exchanges..) that subsequently can strongly impact on the phenotype. We developed a strategy, based on comparative genomic approaches and reconstruction algorithm that allows to pinpoint on a given phylogenetic tree, the time where the events occurred and a description of the events (Gouret et al. 2009, 2011). The evolutionary events can be correlated with each others using comparative phylogenetic-based method in order to reveal putative functional links between the genes (for example two genes that have been lost in a repetitive manner may be a part of the same biochemical cascade). All the processes have been automatized using the in-house expert system called DAGOBAH (Dainat et al. 2012; Gouret et al. 2011). DAGOBAH has been used on the available chordate genomes and all the different events have been evidenced (Paganini et al. 2012 and ioda.univ-provence.fr). I will focused my talk on a specific analysis performed on the genes i) that have been lost and co-loss (or pseudogenised) in a recurrent manner and ii) genes that have been lost (or pseudogenized) during the vertebrate transition from water to land.
- Dainat J, Paganini J, Pontarotti P, Gouret P. 2012. GLADX: An automated approach to analyze the lineage-specific loss and pseudogenization of genes PLoS ONE. In press.
- Gouret P, Paganini J, Dainat J, Louati D, Darbo E, Pontarotti P, Levasseur A. 2011. Integration of evolutionary biology concepts for functional annotation and automation of complex research in evolution: the multi-agent software system DAGOBAH Springer & Pontarotti Pierre (Ed.) 71-87
- Gouret P, Thompson J, Pontarotti P. 2009. PhyloPattern: regular expressions to identify complex patterns in phylogenetic trees. BMC Bioinformatics. 10: 298.
- Levasseur A, Paganini J, Dainat J, Thompson J.D., Poch O., Pontarotti P, Gouret P. 2012. The chordate proteome history database. Evolutionary Bioinformatics. In press.
Evolution of the cecal appendix across mammalian species
Symposium « Médecine et physiologie »
Communication invitée
Heather F. Smith, Department of Anatomy, Arizona College of Osteopathic Medicine, Midwestern University, 19555 N. 59th Ave., Glendale, AZ 85308 U.S.A. E-mail: hsmith@midwestern.edu
William H. Parker, Department of Surgery, DUMC 3704, Duke Medical Center, Durham, NC 27710 U.S.A.
Sanet H. Kotzé, Department of Biomedical Sciences, Faculty of Health Sciences, University of Stellenbosch, P.O. Box 19063, Tygerberg, 7505, Cape Town, South Africa
Michel Laurin, UMR 7207, CNRS/MNHN/UPMC, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Muséum National d’Histoire Naturelle Batiment de Géologie Case postale 48 43 rue Buffon F-75231 Paris cedex 05 France
The cecal (“vermiform”) appendix has been viewed variably as a vestige of unknown function or a remnant of a formerly utilized digestive organ; however, several lines of evidence have recently emerged pointing toward an adaptive nature of this structure. The knowledge that all frugivorous (fruit-eating) great apes possess an appendix has led to the suggestion that the appendix may have evolved in response to reduction in dietary fiber content and the concomitant reduction in cecal size between extant apes and their more folivorous ancestors. Alternatively, the histological composition of the appendix has led to the hypothesis that it may serve an important immunological function, especially in highly social species where the transmission of communicable pathogens is of greater concern. In particular, the recently described biofilm in the appendix walls may suggest that the appendix functions as a safe-house for storing commensal bacteria during times of gastrointestinal distress. To address these hypotheses regarding the origins of this anatomical structure and to assess its correlation with other biological and behavioral variables, a large database was compiled for 361 mammalian species, and the evolution of the appendix was evaluated in association with dietary, social, and gastrointestinal anatomical characters. In species possessing an appendix, a significant, positive correlation was found between changes in the relative length of the appendix and changes in the length of the cecum and colon, thus refuting the hypothesis that the appendix has evolved in response to reduction in dietary fiber content and the concomitant reduction in cecal size. Further supporting this idea, no correlation was found between appearance of an appendix and evolutionary changes in diet, fermentation strategy, or coprophagia. No correlation was revealed between appendix appearance and either social group size or activity pattern, suggesting that species living in larger groups or awake more during the day do not evolve appendices at higher rates than their less social or nocturnal counterparts. Additionally, there was no correlation between appendix appearance and cecum or colon size, cecal shape or cecal haustrations, or colonic separation mechanism, suggesting that other gastrointestinal traits are not driving appendix evolution. This might suggest that the function of the appendix is to some extent independent of the factors evaluated here, or dependent on a complex combination of such factors. However, the appendix was also found to have evolved more often that would be expected by chance alone, a minimum of 32 times, possibly as many as 38 times, but lost fewer than 7 times. This relatively frequent appearance of the appendix in evolution indicates that the structure either has a positive fitness value or is closely associated with another character which has a positive fitness value. Thus, while the dietary and sociality hypotheses for appendix evolution are not supported across mammals, the appendix still appears to be an adaptive structure.
Searching for species of prokaryotes – thoughts of a microbial ecologist who turned chief editor of a major systematics journal
Session communications libres
Communication invitée
Aharon Oren, Department of Plant and Environmental Sciences, The Institute of Life Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel. E-mail: aharon.oren@mail.huji.ac.il
For a microbial ecologist without any formal training in biological systematics to become Editor-in-Chief of the International Journal of Systematic and Evolutionary Microbiology is not the most obvious thing. In spite of the fact that I have performed different functions in the International Committee on Systematics of Prokaryotes and have handled papers describing new taxa of Bacteria and Archaea for many years as an editor for different journals, I am still wondering how to define species of prokaryotes. No generally accepted species concept exists yet for the prokaryotes. Currently the description of new species is based on a polyphasic approach, taking into account phenotypic, chemotaxonomic and genotypic properties. Comparison of small-subunit ribosomal RNA sequences is insufficient to delineate species, and the operational definition of a species based on DNA-DNA hybridization is also not always satisfactory. I will present examples from the halophilic Archaea of the family Halobacteriaceae, showing how species concepts have changed over the years and how the occurrence of lateral gene transfer events and even the formation of recombinant hybrids complicate the delineation of species. While the taxonomy of many groups of prokaryotes is still problematic, their nomenclature is very well ordered based on the rules of the International Code of Nomenclature of Prokaryotes. Thanks to central registration and indexing, the number of names of species, genera, families, orders and classes with standing in the nomenclature of prokaryotes is known at any moment. However, the names of the higher taxa of prokaryotes are currently not covered by the rules of that Code. The nomenclature of one group of prokaryotes is still highly problematic, and that is the Cyanobacteria, a group is traditionally covered by the International Code of Botanical Nomenclature. I will explain the status of our current attempts to achieve a nomenclature system for the Cyanobacteria/Cyanophyta that should become compatible with both Codes.
Divergence-time estimation using fossils as terminal taxa and the origins of Lissamphibia
Symposium « Datations moléculaires et paléontologiques »
Communication invitée
R. Alexander Pyron, Department of Biological Sciences, The George Washington University, 2023 G St. NW, Washington, D.C., 20052 U.S.A. E-mail : rpyron@colubroid.org
Were molecular data available for extinct taxa, questions regarding the origins of many groups could be settled in short order. As this is not the case, various strategies have been proposed to combine paleontological and neontological data sets. The use of fossil dates as node age calibrations for divergence time estimation from molecular phylogenies is commonplace. In addition, simulations suggest that the addition of morphological data from extinct taxa may improve phylogenetic estimation when combined with molecular data for extant species, and some studies have merged morphological and molecular data to estimate combined evidence phylogenies containing both extinct and extant taxa. However, few, if any, studies have attempted to estimate divergence times using phylogenies containing both fossil and living taxa sampled for both molecular and morphological data. Here, I infer both the phylogeny and the time of origin for Lissamphibia and a number of early tetrapods using Bayesian methods based on a data set containing morphological data for extinct taxa, molecular data for extant taxa, and molecular and morphological data for a subset of extant taxa. The results suggest that Lissamphibia is monophyletic, nested within Lepospondyli, and originated in the late Carboniferous at the earliest. This research illustrates potential pitfalls for the use of fossils as post hoc age constraints on internal nodes and highlights the importance of explicit phylogenetic analysis of extinct taxa. These results suggest that the application of fossils as minima or maxima on molecular phylogenies should be supplemented or supplanted by combined evidence analyses whenever possible.
Evolutionary trends
Symposium « Tendances évolutives »
Communication invitée
Michel Laurin, UMR 7207, CNRS/MNHN/UPMC, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Muséum National d’Histoire Naturelle Batiment de Géologie, Case postale 48 43 rue
Buffon F-75231, Paris cedex 05, FRANCE. E-mail : michel.laurin@upmc.fr
Some of the most basic questions about the history of life concern evolutionary trends. These include determining whether or not metazoans have become more complex over time, whether or not body size tends to increase over time (the Cope–Depéret rule), or whether or not brain size has increased over time in various taxa, such as mammals and birds. Despite the proliferation of studies on such topics (some of which will be summarized), assessment of the reliability of results in this field is hampered by the variability of techniques used and the lack of statistical validation of these methods. To solve this problem, simulations are performed using a variety of evolutionary models (gradual Brownian motion, speciational Brownian motion, and Ornstein–Uhlenbeck), with or without a drift of variable amplitude, with variable variance of tips, and with bounds placed close or far from the starting values and final means of simulated characters. These are used to assess the relative merits (power, Type I error rate, bias, and mean absolute value of error on slope estimate) of several statistical methods that have recently been used to assess the presence of evolutionary trends in comparative data. Results show widely divergent performance of the methods. The simple, nonphylogenetic regression (SR) and variance partitioning using phylogenetic eigenvector regression (PVR) with a broken stick selection procedure have greatly inflated Type I error rate (0.123–0.180 at a 0.05 threshold), which invalidates their use in this context. However, they have the greatest power. Most variants of Felsenstein’s independent contrasts (FIC; five of which are presented) have adequate Type I error rate, although two have a slightly inflated Type I error rate with at least one of the two reference trees (0.064–0.090 error rate at a 0.05 threshold). The power of all contrast-based methods is always much lower than that of SR and PVR, except under Brownian motion with a strong trend and distant bounds. Mean absolute value of error on slope of all FIC methods is slightly higher than that of phylogenetic generalized least squares (PGLS), SR, and PVR. PGLS performs well, with low Type I error rate, low error on regression coefficient, and power comparable with some FIC methods. Four variants of skewness analysis are examined, and a new method to assess significance of results is presented. However, all have consistently low power, except in rare combinations of trees, trend strength, and distance between final means and bounds. Globally, the results clearly show that FIC-based methods and PGLS are globally better than nonphylogenetic methods and variance partitioning with PVR. FIC methods and PGLS are sensitive to the model of evolution (and, hence, to branch length errors). The results suggest that regressing raw character contrasts against raw geological age contrasts yields a good combination of power and Type I error rate. They also suggest that to detect evolutionary trends in a comparative dataset, the phylogeny (with estimated branch lengths) is required, and that the data need to be temporally spread (fossils need to be included). In other words, trends cannot be detected from data restricted to extant taxa because the tree is ultrametric.
Evolution and development of digit loss in archosaurs
Symposium « Evo-devo »
Communication invitée
de Bakker, M.A.G., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands.
Fowler, D.A., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands / Current address: Redpath Museum, McGill University, 859 Rue Sherbrooke Ouest, Montreal, Quebec Canada H3A 2K6 and Department of Biology, McGill University, Stewart Biology Building, 1205 Docteur Penfield Montreal, Quebec Canada H3A 1B1.
den Oude, K., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands.
Dondorp, E.M., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands. / Current address: Netherlands Centre for Biodiversity Naturalis, p.o. box 9517, 2300 RA Leiden, The Netherlands.
Garrido Navas, Mª. C., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands. / Departamento de Genética e Instituto de Biotecnología, Universidad de Granada Laboratorio 127 CIBM, Centro de Investigación Biomédica, Avenida del Conocimiento, 18100 Armilla, Granada, Spain.
Horbanczuk, J.O., Institute of Genetics and Animal Breeding, Polish Academy of Sciences, 05-552 Jastrzębiec, Poland.
Szczerbińska D., Department of Poultry and Ornamental Bird Breeding Judyma, Western Pomeranian Univeristy of Technology, 20 street 71-466 Szczecin, Poland.
Sire, J.-Y., Evolution & Développement du squelette, UMR 7138, Université Pierre et Marie Curie, 7 Quai Saint-Bernard, Bat A2, Case 5, 75005 Paris, France.
Richardson, M.K., Dept. Integrative Zoology, Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333BE, Leiden the Netherlands. m.k.richardson@biology.leidenuniv.nl
The limb is a classic system for investigating the evolution of development. Most of our knowledge comes from reverse genetic studies in model species. Here, we examine the evolutionary loss of fingers and toes in archosaurs (Nile crocodile and six birds), and analyse underlying changes in developmental gene expression. We identify the loss of the ‘thumb’ (digit I) and its associated gene expression domains, as a directional trend continuing for 120 million years into modern birds (Neoaves). Digit V is also under directional selection, but the underlying developmental pathways are more conservative than those of digit I, persisting for at least 250 million years. Even when all digits except one are lost in evolution (in the adult emu wing), a normal-sized sonic hedgehog domain, and transient digit V sox9 domain, are expressed in development. We propose a model in which structures are lost in evolution by unrolling or ‘involution’, first of the adult phenotype, and last of the early developmental pathways. This model is surprisingly close to Haeckel’s discredited ‘recapitulation’ theory. However, it differs in being modified by the existence of developmental constraints. As a result, natural selection for adult traits has a variable magnitude of effect (developmental penetrance) on developmental mechanisms. These findings may help us understand the complex interaction between adult phenotype, natural selection and embryonic development.
Phylogeny and nomenclature: Change? Hope? Yes, we can!
Symposium « Nomenclature biologique »
Communication invitée
David Marjanović, Research department, Museum für Naturkunde, Invalidenstraße 43, 10015 Berlin, Germany. E-mail: david.marjanovic@gmx.at
Type-and-rank-based nomenclature, governed by the current codes of nomenclature, was originally developed as a compromise that would work under as many philosophies of classification as possible, including essentialist, phenetic, numerological (Quinarianism) and presumably evolutionary approaches (Darwin was a member of the Strickland commission that published the first code of nomenclature in 1842/3). This has saddled us with a system that does not adequately handle any of the approaches which survived into the late 20th century: 1) it assumes a nested hierarchy, making it unable to represent most of the information contained in a phenetic distance matrix; 2) it assumes mutual exclusivity of taxa, making it unable to deal with transitional forms that could be said, e.g. in gradistic “evolutionary taxonomy”, to sit between two taxa or in their overlap; 3) it makes the relationship between nomenclature and phylogeny loose and optional and even constrains it. For example, it does not and cannot provide enough ranks to allow naming as many nested clades as are necessary to talk about a phylogenetic tree, and it insists that an organism cannot be attached to a name unless it is assigned to a species and a genus, even in cases where most species concepts are inapplicable (as is often the case with fossils) and even when a genus name would be redundant or misleading about phylogenetic relationships – the only alternative is a classification as “incertae sedis” even when the “seat” (sedes) of the organism in the phylogeny is very well understood rather than “uncertain”.
As a consequence of these points, type-and-rank-based nomenclature makes it impossible to wholly avoid paraphyletic taxa – even outside the species category. This is at odds with the widespread current practice of avoiding paraphyletic taxa, which aims to fulfill Darwin’s prediction of turning classifications into “genealogies”.
Taxon names are defined in terms of a type and a rank; by allowing only one type per taxon, and because the ranks are not defined, type-and-rank-based nomenclature does not define the limits of taxa. These are left to the artistic judgment of each systematist at any moment, creating an additional and wholly unnecessary source of instability – unmatched today in the nomenclature of any other science or similar endeavor.
As implemented in the current codes, this system of nomenclature presents further problems: 1) Mandatory endings for names at certain ranks require names to change – often in a cascade – when the rank of one name is to be changed, leaving the same name to refer to different taxa in different publications even when there is no disagreement about the phylogeny. 2) Ranks often need to be changed (see 1)) when a newly discovered taxon is to be inserted into a ranked hierarchy. 3) There are different codes for “animals” (International Commission on Zoological Nomenclature 1999), “plants” (McNeill et al. 2005), and “prokaryotes” (Lapage et al. 1992), leading to the frequent problems of intercode homonyms and ambiregnal organisms (which have parallel nomenclatures depending on whether they are considered “animals” or “plants”, or “plants” or “prokaryotes”, by any particular author). Finally, 4) most of the rules of the code for “animals”, even types and priority, do not apply above the family group of ranks, leaving a large and fast-growing amount of names practically ungoverned. The attempt to provide an overarching framework for the codes (Greuter et al. 2011), which would make this hole slightly smaller, is progressing very slowly.
I will present phylogenetic nomenclature, and the International Code of Phylogenetic Nomenclature (“PhyloCode”; Cantino & de Queiroz 2010) which will govern it, as an alternative that is designed for naming parts of phylogenetic trees. It uses definitions that point at one particular ancestor and turn the question “does organism X belong to taxon Y?” into a testable hypothesis free of artistic judgment.
Phylogeny, taxonomy and nomenclature
Symposium « Nomenclature biologique »
Communication invitée
Alain Dubois, MNHN, Systématique & Evolution, UMR 7205 OSEB, Reptiles & Amphibiens, 25 rue Cuvier, 75005 Paris, France
Taxonomic paradigms have changed several times during the history of zoological taxonomy, yet a single nomenclatural system, so-called “Linnaean”, has remained in force all along. It is theory-free regarding taxonomy as it relies on objective ostensional allocation of nomina (scientific names) to taxa through onomatophores (so-called “types”), rather than on intensional definitions of nomina (e.g., “phylogenetic definitions”). Whereas taxa can be cladistically defined by apognoses or cladognoses, nomina are not descriptions, definitions or theories but simple labels designating taxa as recognized in any classification. Under such a system, the allocation of nomina to taxa is automatic, unambiguous and universal, and nomenclature does not infringe upon taxonomic freedom. The rather widespread opinion that this nomenclatural system does not allow to express a taxonomy based on phylogenetic hypotheses, is misleading. It is based on the confusion between taxonomic categories and nomenclatural ranks, and on the wrong belief that, under the International Code of Zoological Nomenclature, ranks have absolute meanings and are permanently attached to nomina. This ignores three important features of this Code, the existence of nominal-series (“groups of names”), the Principle of Coordination and the possible polysemy of nomina. Within a given nominal-series, the same nomen may be used at different ranks according to the phylogenetic hypothesis adopted. Nomenclatural ranks carry no biological or historical information by themselves, and have no absolute meaning across classifications: there exists no equivalence by any criterion between a family of beetles and a family of frogs. Ranks are useful within taxonomy only: not being equivalent by any criterion, ranks cannot be used for extrataxonomic comparisons. Beside their role in the information storage and retrieval of taxonomic data, the unique, but very important, function of nomenclatural ranks, if used correctly, is to express relationships, and particularly sister-taxa relationships, between taxa under a phylogenetic hypothesis. Taxonomic subordination, parordination and superordination, expressed by ranks, reflect the structure of the cladogram. The lability of rank allocation of nomina under the Code allows taking into account the (permanent) changes in our phylogenetic data and hypotheses. This provides a great flexibility to this nomenclatural system, which is theory-free and can follow easily any changes in taxonomic paradigms. It is therefore much superior to all theory-bound nomenclatural systems in which nomina are rigidly tied to intensional definitions of the taxa for which they were proposed.
Testing the impact of calibration on molecular divergence times
Symposium « Datations moléculaires et paléontologiques »
Communication orale
Hervé Sauquet, Université Paris-Sud, Laboratoire Écologie, Systématique, Évolution, CNRS UMR 8079, 91405 Orsay, FRANCE. E-mail: herve.sauquet@u-psud.fr
Although temporal calibration is widely recognized as critical for obtaining accurate divergence-time estimates using molecular dating methods, few studies have evaluated the variation resulting from different calibration strategies. Depending on the information available, researchers have often used primary calibrations from the fossil record or secondary calibrations from previous molecular dating studies. In analyses of flowering plants, primary calibration data can be obtained from macro- and mesofossils (e.g., leaves, flowers, and fruits) or microfossils (e.g., pollen). Fossil data can vary substantially in accuracy and precision, presenting a difficult choice when selecting appropriate calibrations. Here, we test the impact of eight plausible calibration scenarios for Nothofagus (Nothofagaceae, Fagales), a plant genus with a particularly rich and well-studied fossil record. To do so, we reviewed the phylogenetic placement and geochronology of 38 fossil taxa of Nothofagus and other Fagales, and we identified minimum age constraints for up to 18 nodes of the phylogeny of Fagales. Molecular dating analyses were conducted for each scenario using maximum likelihood (RAxML + r8s) and Bayesian (BEAST) approaches on sequence data from six regions of the chloroplast and nuclear genomes. Using either ingroup or outgroup constraints, or both, led to similar age estimates, except near strongly influential calibration nodes. Using ‘early but risky’ fossil constraints in addition to ‘safe but late’ constraints, or using assumptions of vicariance instead of fossil constraints, led to older age estimates. In contrast, using secondary calibration points yielded drastically younger age estimates. This empirical study highlights the critical influence of calibration on molecular dating analyses. Even in a best-case situation, with many thoroughly vetted fossils available, substantial uncertainties can remain in the estimates of divergence times. For example, our estimates for the crown-group age of Nothofagus varied from 13 to 113 Ma across our full range of calibration scenarios. We suggest that increased background research should be made at all stages of the calibration process to reduce errors wherever possible, from verifying the geochronological data on the fossils to critical re-assessment of their phylogenetic position.
Evolution of fruit types in the tribe Chiococceae: a remarkable example within the family Rubiaceae
Symposium: Character correlation and comparative biology
Communication orale
Piero G. Delprete, Institut de Recherche pour le Développement (IRD), UMR AMAP, Herbier de Guyane, Cayenne, French Guiana, France; email: piero.delprete@ird.fr
Sushil K. Paudyal, Old Dominion University, Department of Biological Sciences, Norfolk, Virginia, USA; email: SPaudyal@odu.edu
Timothy J. Motley, Old Dominion University, Department of Biological Sciences, Norfolk, Virginia, USA; email: TMotley@odu.edu
Historical classifications have treated fruit characters as a set of traits with cardinal taxonomic significance. However, molecular phylogenetic studies have shown that certain fruit characters are more evolutionarily plastic than previously thought. The tribe Chiococceae, as widely delimited according to phylogenetic studies, is a remarkable example of fruit evolution within the family Rubiaceae. This tribe includes about 28 genera and 190 species primarily concentrated in the Greater Antilles (nearly 70% of the species), Central and South America, and in the western Pacific (four genera). Previous molecular studies and our present study demonstrated that it is a strongly supported monophyletic group. Our recent molecular phylogenies, produced with additional molecular markers, provide better resolution within the tribe and allowed us to examine fruit evolution within the tribe with increased confidence. According to our results, the ancestral fruit type of the Chiococceae is a many-seeded capsule, and that placentation, seed shape and position evolved within the lineage into several different forms among the genera with capsular fruits. Within the Portlandia clade, a group of genera with capsular fruits, the fruits of Catesbaea evolved into leathery berries. Both of these fruit types have axial placentation, and although the fruits of the genera of Portlandia clade are woody and dehiscent, those of Catesbaea are either fleshy or leathery, and indehiscent. Within the Chiococca clade, two events where drupaceous fruits evolved from capsular fruits have been detected, once in Phialanthus, and a second time in the Chiococca group, where all the genera have drupaceous fruits. The passage from capsular to drupaceous fruits also involves the evolution from axial placentation, with seeds peltate to the placenta, to pendulous seeds attached near the roof of the ovary. Additionally, the fruit type appears to be correlated with the geographical distribution of the tribe, because the genera in the Pacific have capsular fruits with wind-dispersed seeds, which is an obvious adaptation to long-distance dispersal.
Dialogue de l'anatomie comparée, de la biologie moléculaire et des fossiles : le cas de la phylogénie des acanthomorphes (Vertebrata, Actinopterygii, Teleostei)
Session communications libres
Communication orale
Donald Davesne, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, UMR 7207, Muséum national d’Histoire naturelle département Histoire de la Terre, CP 38, 8 rue Buffon, 75231 Paris Cedex 05, France et UMR 7138, Muséum national d'Histoire naturelle département Systématique et Évolution, CP 26, 43 rue Cuvier 75231 Paris Cedex 05, France. Email : dondavesne@orange.fr
Cyril Gallut, UMR 7138, Muséum national d'Histoire naturelle département Systématique et Évolution, CP 26, 43 rue Cuvier 75231 Paris Cedex 05, France. Email : cyril.gallut@upmc.fr
Olga Otero, UMR 6046, Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements, Université de Poitiers Faculté des Sciences Fondamentales et Appliquées, 40 av. du Recteur Pineau, F-86 022 Poitiers Cedex, France et Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, UMR 7207, Muséum national d’Histoire naturelle département Histoire de la Terre, CP 38, 8 rue Buffon, 75231 Paris Cedex 05, France. Email : ootero@mnhn.fr
Acanthomorphs form a major clade of teleosts which account for one quarter of the extant vertebrate species. Their deep interrelationships are poorly understood and are a subject of intense research.
Acanthomorph monophyly has been questioned in a series of recent mitogenome-based studies. This result, although contradicting the anatomical hypotheses, has not been discussed by either anatomists or molecular phylogeneticists with a suitable sampling.
In the present work, we re-evaluated large-scale phylogeny of the Acanthomorpha. A new anatomical dataset has been produced, with a sampling representing most of the major acanthomorph clades that includes incertae sedis Cenomanian (Upper Cretaceous) fossils for the first time. It has been analysed with parsimony and three-item analysis (3ia).
We also produced a molecular dataset with complete mitogenomes and a similar sample of taxa. It has been analysed with parsimony and Bayesian inference.
The anatomical results strongly support acanthomorph monophyly, with four unambiguous synapomorphies. Several molecular-based clades were found on the basis of our anatomical characters. The fossil specimens, with their unique mosaic of characters, allow for improved resolution and node support. Molecular results are different depending on the phylogenetic method used: Acanthomorpha are monophyletic with Bayesian inference but not according to parsimony. This second result contradicts previous mitogenome-based studies.
The congruence between anatomy-based parsimony results and molecular-based Bayesian results is a strong argument in favour of acanthomorph monophyly.
Contributions to the molecular phylogeny of Thelypteridaceae with special reference to Neotropical taxa
Poster
Thaís Elias Almeida, Department of Botany, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 – Belo Horizonte, Minas Gerais, Brazil. Post office box 486, zip code 30123-970. blotiella@gmail.com
Alexandre Salino, Department of Botany, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 – Belo Horizonte, Minas Gerais, Brazil. Post office box 486, zip code 30123-970. salinobh@gmail.com
João Aguiar Nogueira Batista, Department of Botany, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 – Belo Horizonte, Minas Gerais, Brazil. Post office box 486, zip code 30123-970. janb@icb.ufmg.br
Sabine Hennequin - UMR 7207 UPMC CNRS MNHN - Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements, 43 rue Buffon, CP 48, F-75231 Paris cedex 05. shennequ@snv.jussieu.fr
Harald Schneider, Botany Department, Natural History Museum, Cromwell Road, London, SW7 5BD. h.schneider@nhm.ac.uk
Aline Joseph Ramalho, Department of Botany, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 – Belo Horizonte, Minas Gerais, Brazil. Post office box 486, zip code 30123-970. alinejr@gmail.com
Karina Proite, Department of Botany, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 – Belo Horizonte, Minas Gerais, Brazil. Post office box 486, zip code 30123-970. kproite@gmail.com
Thelypteridaceae is one of the largest fern families with about 950 species and a cosmopolitan distribution, with most species occurring in tropical and subtropical regions. Its generic classification remains controversial: different authors recognize from only one to 25 genera. In addition, the phylogenetic relationships within the family have been poorly studied: in the major publication on the family, Smith and Cranfill (2002) conclude that Thelypteridaceae (excluding Hypodematium) is monophyletic, but their sampling is preliminary and insufficient to support any of the many existing classifications for the family. In order to improve our phylogenetic knowledge of Thelypteridaceae and to help support more accurate generic classifications, we propose to expand the molecular phylogeny of the family using principally Neotropical representatives. We also test the monophyly of the exclusive or mostly Neotropical genera Amauropelta, Goniopteris, Meniscium and Steiropteris. Our sampling includes 70 taxa and 158 sequences obtained from two plastid (rps4 and trnL-F) genome regions, resulting in a matrix of 2224 molecular characters. The combined data set was analysed using parsimony and Bayesian inferences. Our results are congruent with the results found in other studies, as those of Smith & Cranfill (2002) and Alvarez-Fuentes (2010), in that we recover the monophyly of Thelypteridaceae and of two main lineages within the family: the Phegopteroid and the Thelypteroid lineages. All Neotropical groups investigated are retrieved as monophyletic: Amauropelta (with the African species nested within American species), Goniopteris, Meniscium and Steiropteris (including the incertae sedis Thelypteris polypodioides).
la théorie de l’évolution : au-delà de l’arbre phylogénétique ?
Session communications libres
Communication orale
Grand Anaïs, MNHN, UMR7207, CP48 (bat de géologie), 57 rue Cuvier, 75005 Paris.
grand@mnhn.fr
La théorie de l’évolution est centrale en biologie ; formalisée et mise en équation en génétique des populations. En systématique phylogénétique il est très souvent fait appel à des processus évolutifs (telle la spéciation) pour interpréter et justifier la recherche d’arbres phylogénétiques. Il parait donc évident qu’un arbre phylogénétique ne puisse pas être en contradiction avec cette théorie. Pourtant, la théorie de l’évolution, telle qu’elle est formalisée, n’interdit rien au niveau taxique, alors même que l’arbre phylogénétique impose certaines contraintes restreignant les possibles (par exemple, il est dit que les taxons paraphylétiques « n’existent » pas ; cette contrainte étant donc ontologique). Dans le cadre d’une formalisation des théories dite « modèle-théorétique » (approche développée depuis les années 60), une théorie non contrainte ne serait qualifiée que de « structure », alors que l’ajout de contraintes permettrait de passer de la « structure » au « modèle ». Ne pourrait-on pas alors considérer la théorie « taxique » de l’évolution comme une « structure » (c'est-à-dire un ensemble de taxons liés par des relations "descend avec modifications de") à laquelle il serait nécessaire d’ajouter une contrainte ontologique par une démarche phylogénétique (telle la cladistique) ? Et ceci afin de pouvoir la formaliser, au niveau taxique, selon un modèle-théorétique ?
Study of the phylogenetic relationships of the genera in the tribe Cnephasiini (Lepidoptera, Tortricidae, Tortricinae) using morphological characters
Poster
MahboobeHadadian,MSc. Student of Entomology Department, Islamic Azad University, Science and Research Branch, Fars , IRAN, mahboobe_hadadian@yahoo.com
Helen Alipanah, Iranian Research Institute of Plant Protection, P.O.Box 1454, Tehran 19395, IRAN, halipanah@gmail.com
HadiOstovan, Islamic Azad University,Science and Research Branch, Fars, IRAN, P.O.Box: 73715-181, ostovan2001@yahoo.com
AlimoradSarafrazi, Iranian Research Institute of Plant Protection, P.O.Box 1454, Tehran, 19395, IRAN, asarafrazi@yahoo.com
The phylogeny of the tribe Cnephasiini and the relationships of the included genera were examined using 92 (76 binary and 16 multistate) morphological characters of the adults (19 external characters, nine characters for wing venation, 15 abdominal characters of both sexes and 49 genital characters). The study material included 31 species of 25 genera, representing all recognized and accepted genera of Cnephasiini, together with the genera PandemisandChoristoneurafrom the tribe Archipini, andthegenus,Eulia from the tribe Eulini. The two genera Acleris and Tortrix with one species respectively considered as outgroups. The cladistic analysis (with max trees 1000 and 20000 replicates) resulted in 18 equally parsimonious trees (length 254 steps, CI = 0.4921, RI = 0.5757). According to the results of this survey, the representative of the genus Euliawas placed inside the tribe Cnephasiini; the genus Cnephasiawas not found to be monophyletic; the two genera OporopsammaandAmphicoeciaconstituted a clade, with Oxypteronwertheimsteini and Oxypteronpalminiforming their sister clade. We found close affinitiesbetween the generaTortricodesandKawabeia, between the generaExapateandEpicnephasia and between the generaPropriomorphaandXerocnephasia.
R-SYST network : a French consortium for barcoding and species identification
Session communications libres
Communication orale
A. Bouchez, INRA* de Thonon les Bains, UMR CARRTEL , 74203 Thonon , FRANCE. agnes.bouchez@thonon.inra.fr
M. Buée, INRA* de Nancy, UMR IAM , 54280 Champenoux, FRANCE. buee@nancy.inra.fr
P. Chaumeil, INRA *de Bordeaux, UMR BIOGECO, Pierroton, 33612 Cestas , FRANCE. chaumeil@pierroton.inra.fr
V. Laval, INRA*de Grignon, UMR1290 BIOGER-CPP, 78850 Thiverval-Grignon, FRANCE. vlaval@versailles.inra.fr
M. Le Saux5, INRA * d'Angers-Nantes, UMR 1345 IRHS, 49070 Beaucouze, France. marion.lesaux@angers.inra.fr
M.A. Auger-Rozenberg, INRA* d'Orléans, URZF 45, 45075 Orléans, FRANCE. Marie-Anne.Auger-Rozenberg@orleans.inra.fr
the R-SYST consortium
Alain Franc, INRA *de Bordeaux, UMR BIOGECO, Pierroton, 33612 Cestas , FRANCE. Alain.Franc@pierroton.inra.fr
* Institut National de la Recherche Agronomique
R-SYST is a French national network of around a dozen research teams including technicians, researchers and engineers in the fields of molecular biology, genetics and bioinformatics who are involved in the molecular and morphological characterization of organisms. The network's ambition is to develop a dictionary between genetic and phenotypic variability, thus enabling a better characterization of these organisms, and to compare and study informations brought by morphology and molecular biology for systematics and taxonomy. The objective is to develop a series of computer tools (for scientists and non-specialist professionals) for the identification of species based on a network of expertise in the fields of morphological based taxonomy, molecular biology and bioinformatics. The strength of this network is that involved specialists have experience in the description, classification and recognition of organisms from a large panel of taxonomic groups. Currently five groups are included in this network : plant associated bacteria, freshwater micro-algae (diatoms), trees, invertebrates (insects, nematodes) and fungi. Common questions regarding identification are shared between specialists of the different taxa.
R-SYST consortium is also aiming at developing bioinformatics tools for analysis and sharing them via its web site. Our consortium wishes to propose a complete tool suite devoted to identification analysis. One part simply is to deliver user friendly access to classical tools such as alignment and phylogeny inference, and another part is to design tools specifically for species identification based on consistency (or not) between characters and clusters from sequences. One of them presented here is “declic”, which enables clusterization and visualization of a reference sequence data set up to a few thousands specimen. The skeleton of this tool is graph clustering (building communities on graphs), where a graph is produced from a pairwise genetic distance array using a threshold, sometimes referred to as “barcoding gap” in barcoding communities. It is expected that individuals belonging to a same taxa build a clique, and the tool permits an analysis between actual situation and this ideal one. Results will be shown on French Guiana tree flora, and on a freshwater diatom library. Accuracy and reliability of this tool will be discussed.
Évaluation des stratégies d'analyse phylogénétique par la cohérence des résultats
Session communications libres
Communication orale
Blaise LiCentro de Ciências do Mar, Universidade do Algarve,Campus de Gambelas,8005-139 Faro,Portugal, blaise.li@normalesup.org
Dans cette présentation, je propose une idée d'approche visant à identifier parmi un
certain nombre de stratégies d'analyse phylogénétique, appliquées à un ensemble
de jeux de données, celle qui est susceptible de fournir les résultats les plus fiables.
Cette approche se base sur l'hypothèse que plus un résultat est reproduit à partir de
données indépendantes, plus ce résultat reflète le signal historique commun aux données
analysées.
Si une stratégie d'analyse permet d'obtenir un ensemble de résultats plus cohérent qu'une
autre, on peut faire l'hypothèse que sa capacité à extraire le signal historique des
données est meilleure.
J'applique cette approche à une série d'analyses en maximum de vraisemblance utilisant
différents recodages d'ensemble de gènes cyanobactériens et chloroplastiques, et essaie de tirer quelques conclusions de cet essai.
Recent radiation of the ancient cycads
Session communications libres
Communication orale
Nathalie Nagalingum, Royal Botanic Garden Sydney, MrsMacquaries Road, Sydney, NSW, Australia, 2000. nathalie.nagalingum@rbgsyd.nsw.gov.au
Cycads have captured wide interest as survivors and relicts from the age of dinosaurs. They are thought to have reached their greatest diversity during the Jurassic-Cretaceous (199.6-65.5 Ma), then dwindling to their present diversity of ~300 species as flowering plants rose to dominance. However, fossil-calibrated molecular phylogenies demonstrate that living cycad species are not at all ancient. Instead they diversified recently, with radiations beginning ~12 million years ago. The parallel radiations within multiple genera are nearly synchronous and are global. Just as remarkably, they ceased to diversify. These findings indicate that cycads likely responded to a change in global climate occurring 12 million years ago. These data reject the hypothesized role of dinosaurs in generating extant diversity and the designation of today’s cycad species as living fossils.
New unicellular with mineral test: a bioeroding epibiont of extent and fossil crustaceans.
Poster
Robin Ninon, Bâtiment de Géologie UMR 7207, Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), CP48 43 rue Buffon, 75231 Paris cedex. ninonrobin@neuf.fr
Petit Gilles, Bâtiment de Géologie UMR 7207, Centre de Recherche sur la Paléobiodiversité
et les Paléoenvironnements (CR2P) CP48 43 rue Buffon, 75231 Paris cedex. gilles.petit@upmc.fr
Charbonnier Sylvain, UMR 7207, Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P)
8, rue Buffon, 75005 PARIS, France. scharbonnier@mnhn.fr
Interspecific relationships are crucial factors in the evolution of species. These relationships studied in the fossil record are mainly epibiosis associations (action to "live on" another organism) easily detectable on the specimens unlike endobiosis. The observation by light microscopy and scanning of microfossils on shrimps from La Voulte-sur-Rhône (Callovian) allowed us to describe a totally new association: still unknown unicellular eukaryotes, with mineral test, able to erode and even perforate the cuticle of the shrimp Archeosolenocera straeleni (Carriol & Riou, 1991). This association has been analyzed through the discovery of a previously undescribed similar epibiosis on the extent shrimp Farfantepenaeus brevirostris (Kingsley, 1878) from the Gulf of Mexico. The forms observed in the extent and the fossil record are flat bioeroding disks, 150 to 500 microns in diameter, firmly embedded in the cuticle. The study on extent record also shows some forms divided by bipartition, a growth of the disc-shaped forming expansions able to pass completely through the cuticle, and then to multiply by intense budding. The development cycle on the shrimp recalls the life cycle of some benthic foraminifera but the test of epibionts lacks the perforations required for the passage of filopodia, proper to foraminifera. The of a mineral discoid test and the division by bipartition evokes some testate amoebae like arcellids, but the similarity stops there. Among fossil organisms, the gilianelles are also in the form of flat disks, but they are free and show also openings on two sides. For these differences, the organisms studied appear to belong to a new taxon unknown in the past history and the extent life. Further studies are expected to fully describe the development cycle and to suggest a systematic position. The relationship between the crustacean and its epibiont is close to commensalism, which promotes the renewal of food resources and the dissemination of the epibiont without constraining the host. But it is also at the limit of parasitism because perforation of the integument and the loss of hydrodynamics can promote predation. This work highlights the need to push further the study of crustaceans epibiosis in both fossil record and in extent world.
Molecular taxonomy and phylogeny of Nasutitermes species (Termitidae: Nasutitermitinae) in French Guiana with emphasis on pest species recognition
Poster
Virginie Roy, Vincent Chassany, Stéphanie Giusti, Michel Diouf, Philippe Mora et Myriam Harry
roy@u-pec.fr
Termites of the Nasutitermes genus are dominant taxa in Neotropical primary forests but also represent major agricultural and structural pests in anthropized areas. Despite their prevalence, pivotal ecological role and economical impact, the taxonomy and evolutive history of Nasutitermes taxa mainly depend on confounding morphological characters. Even the widespread species such as N. corniger are often misidentified. In this study mitochondrial and nuclear sequences (cytochrome oxidase I, cytochrome oxidase II, 16S rDNA and internal transcribed spacer 2) were analyzed from colonies of Nasutitermes collected throughout French Guiana, South America. We present a molecular taxonomic and phylogenetic analysis for Guyanese species, including eight species described as pests in South America.
Heterozygosity as a key to delineate species
Session communications libres
Communication orale
Jean-François Flot, Max Planck Institute for Dynamics and Self-Organization, Bunsenstr.10, 37073 Göttingen, Allemagne. jflot@gwdg.de
Delimiting species is a core problem in biology and a variety of criteria have been proposed to solve it: population genetic approaches look for barriers to gene flow between populations and are therefore directly inspired from the biological species criterion, in contrast to phenetic and phylogenetic approaches that focus on delineating clusters of similar individuals or reciprocally monophyletic groups (or even, as do barcoding approaches, restrict themselves to groups or clusters that are more divergent than a certain distance threshold from one another). Another striking difference between these approaches concerns their attitude towards heterozygosity (i.e., the co-occurrence in diploid individuals of several character states for a given molecular character): whereas heterozygosity is instrumental to population genetic approaches, it is usually ignored in phenetic, phylogenetic and barcoding approaches that either focus on haploid markers or, when looking at diploid loci, tend to minimize the importance of intra-individual sequence variation.
It is precisely because population genetic approaches make use of the information provided by heterozygosity that they are so powerful: notably, they are able to delineate species that are not monophyletic for the markers under investigation, a frequent situation that traditional tree-based approaches are not equipped to deal with. However, a drawback of population genetic approaches is that they require examining a large number of markers (typically tens) and an even larger number of individuals (typically tens or hundreds per species), making them impractical to use in large-scale taxonomic studies. This is why I propose to incorporate heterozygosity in tree-based approaches: adding connections on a tree between the sequences found co-occurring in heterozygous individuals makes it possible to visually delineate groups of individuals whose ancestors have been exchanging genes through the process of sexual reproduction. Examples of application of this “haploweb” approach to species delimitation in tropical corals and freshwater amphipods will be presented.
How to detect heterochronies ?
Symposium « Evo-devo »
Communication orale
Michel Laurin, UMR 7207, CNRS/MNHN/UPMC, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Muséum National d’Histoire Naturelle Batiment de Géologie, Case postale 48 43 rue Buffon F-75231, Paris cedex 05, FRANCE. michel.laurin@upmc.fr
The field of evo-devo has largely benefitted from the recent progress in phylogenetics, as shown by the recent development of methods that use phylogenies to determine on which branch of the evolutionary tree a heterochrony took place. Among these methods, the most widely used is no doubt event pairing, which consists in decomposing developmental sequences into ordered pairs of events. This methods has drawbacks because it discards data, and it is difficult to use because for n events, it generates n(n-1)/2 characters. Thus, for a sequence of 10 events, 45 characters are produced, and for 20 events, this number grows to 190. A simpler treatment is possible, such as a « continuous analysis », a recently described method. This procedure consists in standardizing developmental time or sequence position. Ancestral developmental times or sequence positions can then be inferred using squared-change parsimony, and confidence intervals can be inferred using the phylogenetic independent contrasts. This method exploits branch length data (contrary to event pairing), in addition to the topology. A simulation-based study shows that the new method is more powerful and has a lower type I error rate than event pairing, in addition to being easier to use. Recently, this method has been used to refute the hypothesis that the temnospondyl Apateon was very similar to the ancestral urodele in its cranial ossification sequence. This method also better captures the phylogenetic signal in developmental data, as shown by another simulation-based study.
Entre résilience et sérendipité, l'espèce
Session communications libres
Communication orale
Philippe Lherminier, Château du Fontenil, 61300 L'Aigle - tel 02 33 24 46 68 - email phlherminier@wanadoo.fr
De toutes les questions que pose l'évolution des espèces l'une des plus insolites est celle de leur stabilité. En général les relations qui unissent les membres d'une espèce se perpétuent inchangées pendant des durées immenses. Il arrive que les limites de l'espèce soient franchies mais pour ces égarés et transgresseurs la mort est la solution habituelle. La résilience d'une espèce est l'ensemble des propriétés anti-aléatoires ou homéostatiques qui maintiennent l'ordre des relations, donc l'unité et la stabilité. Cependant il arrive qu'un nouvel ordre de relations se substitue au précédent, non pas en continuité avec l'espèce initiale mais en rupture. L'isolement de l'espèce nouvelle survient en quatre étapes : barrière géographique s'opposant au brassage et produisant une dérive aléatoire, divergence adaptative et écologique majeure, mutations affectant la cour sexuelle, et accidents génétiques, la fécondité. La sérendipité, définie comme l'usage intelligent du hasard, s'applique à cet ensemble de hasards et de rencontres imprévues et si lourdes de conséquences appelé spéciation. L'espèce nouvelle est une « invention » qui émerge par le réemploi inattendu et opportun des aptitudes ancestrales – peut-être l'essence de l'évolution. Le rapport résilience conservatrice / sérendipité novatice est illustrée par plusieurs exemples : les animaux domestiques, le mimétisme, les insectes phytophages, les polyploïdes, puis étendu à un modèle général de spéciation. Enfin les rapports avec l'intelligent design doivent être clarifiés : la sérendipité comme la résilience ne sont pas des vertus ordonnatrices présentes et à l'oeuvre dans la nature (ni au-dessus), ce sont des catégories de jugement.
Evolutionary history of a 10,000-species clade of angiosperms:reconstructing the phylogeny of magnoliids as a whole
Session communications libres
Communication orale
Massoni, Julien, Universite Paris-Sud 11, Lab. Ecologie, Systematique, Evolution (ESE), CNRS UMR 8079, Bat. 360, Orsay, N/A, 91405, France. massoni.julien@gmail.com
Forest, Felix, Royal Botanic Gardens - Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3DS, United Kingdom. F.Forest@kew.org
Sauquet, Hervé, Universite Paris-Sud 11, CNRS UMR 8079, Bat. 360, Orsay, N/A, 91405, France. herve.sauquet@u-psud.fr
Large-scale phylogenetic studies conducted over the last two decades have clarified phylogenetic relationships at the base of the angiosperm tree. This new context led to the definition of a new early-diverging clade referred to as magnoliids or Magnoliidae. This monophyletic group is made up of four orders (Canellales, Piperales, Laurales,and Magnoliales) and 20 families, including well-known species such as avocado, pepper or nutmeg. The 10,000 species of Magnoliidae show considerable diversity of floral shapes. Despite the fact that this clade is supported by the great majority of large-scale phylogenetic studies based on molecular and morphological data, no detailed phylogenetic analysis of the group as a whole has been conducted yet. We sampled 241 species representing 92% of genus diversity within Magnoliidae, and 12 markers from the three genomes (chloroplastic: atpB,matK, trnL intron, trnL-trnF spacer, ndhF, rbcL; mitochondrial: atp1, matR, mtLSU, mtSSU; nuclear: 18S, 26S). Phylogenetic analyses using maximum parsimony, maximum likelihood, and Bayesian methods yield well resolved trees consistent with previous family-level and higher-level studies. Magnoliidae are separated in two clades: (Piperales+Canellales) and (Laurales+Magnoliales). On the other hand, our analyses resolved a number of long-standing polytomies. These results highlight the importance of a large taxonomic and molecular sample to resolve both deep and shallow phylogenetic relationships within Magnoliidae. This study is the first step toward a robust and accurate phylogenetic framework needed to reconstruct patterns of floral evolution in this clade.
Phylogenetic signal in bone histology of amniotes revisited
Symposium: Character correlation and comparative biology
Communication orale
Lucas Legendre, UPMC, Univ. Paris 06, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France and CNRS, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France. Email: lucas.legendre@upmc.fr
Nathalie Le Roy, UMR CNRS 6282 Biogeosciences, Univ. Bourgogne, 6 bd Gabriel, Dijon 21000 France. E-mail: nathalie.le-roy@u-bourgogne.fr
Cayetana Martinez-Maza, Department of Paleobiology, Museo Nacional de Ciencias Naturales – CSIC, Madrid, Spain. E-mail: martinezmaza.cayetana@gmail.com
Laetitia Montes, UPMC, Univ. Paris 06, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France and CNRS, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France. Email: laetitia.montes-poloni@live.fr
Michel Laurin, CNRS UMR 7207, MNHN, bâtiment de géologie. BC 45. 43 rue Buffon, 75005 Paris, France. E-mail: michel.laurin@upmc.fr
Jorge Cubo, UPMC, Univ. Paris 06, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France and CNRS, UMR 7193, ISTeP, 4 place Jussieu, BC 19, F-75005, Paris, France. E-mail: jorge.cubo_garcia@upmc.fr
There is currently a debate about the presence of a phylogenetic signal in bone histological data; however, very few reliable statistical tests have been performed on large histological datasets. Here, we performed new analyses using a larger set of seven histological traits measured on 25 taxa (9 extinct and 16 extant taxa) in the clade Amniota, using three different methods: the phylogenetic eigenvector regression, the tree length distribution and the regressions on distance matrices.
Our results clearly show that the phylogenetic signal in our sample of bone histological characters is strong, even after correcting for multiple testing. Most characters exhibit a significant phylogenetic signal according to at least one of our three tests, with the phylogeny often explaining 20–60% of the variation in the histological characters. Cubo et al. (2012) found a significant functional effect on bone histological variation for a similar large histological dataset that are complementary to the evidence presented here for a significant phylogenetic signal on the same traits. Thus, we conclude that the phylogenetic comparative method should be systematically used in interspecific analyses of bone histodiversity to avoid problems of non-independence among observations.
Évolution des gènes impliqués dans les interactions gamétiques chez les vertébrés : mise en évidence de sélection positive, duplications et pertes
Symposium « Évolution moléculaire »
Communication orale
Camille Meslin *,a,b,c,d, Sylvie Mugnier *,e, Isabelle Callebaut f, Michel Laurin g, Géraldine Pascal a,b,c,d, Anne Poupon a,b,c,d, Ghylène Goudet a,b,c,d et Philippe Monget a,b,c,d.
a INRA, UMR85, Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France.
b CNRS, UMR6175, F-37380 Nouzilly, France.
c Université François Rabelais de Tours, F-37041 Tours, France.
d IFCE, F-37380 Nouzilly, France.
e AgroSup Dijon, Département Agronomie Agro-équipement Élevage Environnement, 21079 Dijon, France.
f IMPMC UMR 7590, Université Pierre et Marie Curie-Paris 6, 75015 Paris, France.
g UMR 7207, CNRS/MNHN/UPMC, Muséum National d’Histoire Naturelle, 75005 Paris, France.
Les gènes qui codent les protéines impliquées dans les interactions entre le spermatozoïde et l’ovocyte évoluent particulièrement vite, ce qui pourrait contribuer à la spéciation. Certains d’entre eux (ZP3, ADAM1, ADAM2, ACR and CD9) évoluent sous sélection positive. Le but de notre travail était d’étudier systématiquement l’évolution des soixante-neuf gènes connus expérimentalement pour être impliqués dans la fécondation chez les vertébrés. Nous avons étudié dix neuf espèces de vertébrés dont le génome a été séquencé, nous avons comparé les espèces à fécondation interne et externe, et distingué les trois étapes principales de ce processus biologique : la liaison spermatozoïde/ovocyte, la réaction acrosomique, et la fusion des membranes gamétiques.
Trente trois gènes parmi les soixante-neuf évoluent sous sélection positive, trente neuf ont au moins un gène paralogue dans une espèce, et dix sept se sont pseudogénisés. Pour quinze d’entre eux, nous n’avons trouvé ni sélection positive, ni duplication, ni pseudogénisation. Par ailleurs, les gènes impliqués dans la liaison des gamètes tendent à être perdus chez les mammifères euthériens, tandis que ceux qui sont impliqués dans la fusion des membranes évoluent sous sélection positive chez les téléostéens. Contrairement aux idées reçues, les euthériens semblent avoir un taux de duplication de gènes plus élevé que les téléostéens. Cependant, ceci résulte de l’incorporation de la longueur des branches dans les analyses; autrement, les téléostéens sembleraient avoir un taux de duplication plus élevé. Enfin, dans les cas de sélection positive et quand cela a été possible, la localisation des acides aminés sous sélection positive sur les structures tridimensionnelles des protéines montre que ceux-ci sont plutôt localisés en périphérie des protéines, ce qui suggère une évolution des interfaces avec des partenaires.
L’ensemble de ces résultats suggèrent qu’il existerait une sorte de signature évolutive des gènes de la fécondation chez les vertébrés.
La Notation Taxonomique Condensée (NTC) : une approche simplifiée de la systématique
Symposium « Nomenclature biologique »
Communication orale
Jacques-Deric Rouault, Laboratoire Evolution, Génomes et Spéciation - LEGS - IDEEV - CNRS UPR9034, 91198 Gif-sur-Yvette, France & Université Paris-Sud 11, 91405 Orsay, France., Jacques-Deric.Rouault@legs.cnrs-gif.fr
Vincent Leignel, Laboratoire Mer-Molécules-Santé EA2170, L’UNAM Université du Maine, Av. Messiaen, 72085 Le Mans cedex9, Vincent.Leignel@univ-lemans.fr
La classification des millions d'espèces vivantes connues est une discipline en perpétuelle évolution, avec des révolutions déchirantes depuis l'usage des phylogénies moléculaires. Au cours de l'évolution de la classification, on peut constater que certains nœuds de l'arbre du vivant sont relativement stables, même si les branches qui les relient peuvent voir leur topologie être de temps à autre bouleversée. Il apparaît que les niveaux stables de la systématique sont : règne, phylum, classe, ordre, famille. L’idée de la Notation Taxonomique Condensée (NTC) est venue du désir de simplifier la lecture de la position systématique des organismes afin de permettre à un large public de déterminer et de retenir avec plus de facilitée la position des organismes dans l’arbre du vivant. Pour ce faire, il est proposé de ne retenir que les trois premières lettres de chacun des niveaux cités précédemment afin de constituer un mot de 15 lettres. Par exemple le terme « MetArtInsDipDro » désigne la famille des Drosophilidae, de l'ordre des Diptères, de la classe des Insectes, du phylum des Arthropodes et du règne des Métazoaires. La Notation Taxonomique Condensée (NTC) peut donc s’appliquer à l’ensemble de la diversité contenue dans l’arbre du vivant et constituer une approche simplifiée de sa codification. Nous présenterons nos premiers résultats de mise en place de ce système NTC.
Phylogenetic patterns in the palm androecium
Session communications libres
Communication orale
Elodie Alapetite, Boris Domenech, Sophie Nadot
Université Paris-Sud 11, UMR8079, Laboratoire Ecologie, Systématique et Evolution. elodie.alapetite@u-psud.fr; boris.domenech@gmail.com; sophie.nadot@u-psud.fr.
Palms (Arecaceae) are an emblematic family of monocots comprising 183 genera and around 2400 species distributed on all continents, throughout tropical and subtropical areas (Dransfield et al. 2008). Their characteristic leaves and stems make palms immediately recognizable in the field. The unconspicuous palm flowers are usually considered as rather dull. They are small (a few centimetres), trimerous, often unisexual, colourless (white or greenish) and grouped into huge inflorescences. However palm flowers exhibit a large diversity in stamen number, diversity that is still poorly understood. Stamen number ranges between a few units (oligandry) to several dozens or even several hundreds of units (polyandry) in some genera (Nadot et al. 2011). We studied the evolution of stamen number in two subtribes of the palm family, namely the Archontophoenicinae and the Ptychospermatinae (subfamily Arecoideae), in which the range of variation in stamen number is particularly high.
Archontophoenicinae and Ptychospermatinae are naturally distributed in the South West Pacific area and contain respectively 6 genera (15 species) and 12 genera (68 species). In order to obtain a detailed phylogenetic framework for our study, we produced molecular phylogenies of each of the subtribes. Despite major advances in palm phylogeny reconstruction (Baker et al. 2009), a well resolved tree of Arecoideae is still lacking and relationships among and within genera need to be clarified. We sequenced nuclear markers, the AGAMOUS gene, nrITS2, a conserved nuclear intron (rice chromosome 10), and regions from two low-copy genes, phosphoribulokinase (PRK) and subunit 2 of RNA polymerase II (RPB2). We also used plastid markers, mainly matK, ndhA and rps15-ycf1. For PRK and RPB2 our data set was completed with sequences retrieved from GenBank.
The combination of all these markers resulted in improving the resolution and robustness of phylogenetic relationships within each subtribe. The nuclear markers proved particularly helpful in assessing the monophyly of the genera and improving our knowledge of the phylogenetic relationships among genera. Optimisation of stamen number on the two phylogenies revealed a high level of inter-specific (and often intra-specific) variability, making it difficult to detect trends toward increase or decrease in stamen number, particularly in the Archontophoenicinae. The reason why stamen number varies so extensively in these two groups is still unknown and needs further investigation into the ecology and pollination biology of these species.
PAUP vs TNT : approche bibliographique comparative de l’emploi des deux logiciels de parcimonie les plus utilisés de nos jours
Session communications libres
Communication orale
Fabrice Fack1, Elise Tancoigne2, Sandrine Ladevèze1, Damien Germain1 et Véronique Barriel1
1 UMR 7207, CNRS/MNHN/UPMC, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Département Histoire de la Terre, Muséum National d’Histoire Naturelle, Case postale 38, 8 rue
Buffon, 75005 Paris, France.
2 UMR 7205, MNHN/CNRS, Origine, Structure et Evolution de la Biodiversité, Département Systématique et Evolution, Muséum National d’Histoire Naturelle, Case postale 30, 25 rue Cuvier, 75005 Paris, France.
E-mails : Fabrice Fack : fack@mnhn.fr, Elise Tancoigne : tancoigne@mnhn.fr, Sandrine Ladevèze : ladeveze@mnhn.fr, Damien Germain : germain@mnhn.fr, Véronique Barriel : barriel@mnhn.fr
Il existe aujourd’hui de nombreux logiciels d’analyse phylogénétique permettant de réaliser des analyses de parcimonie. Le but de notre étude est de déterminer parmi ces logiciels lesquels sont les plus employés aujourd’hui. Pour cela, nous avons dans un premier temps effectué un recensement des logiciels utilisés dans les articles de phylogénie publiés dans 4 revues : Cladistics, Molecular Phylogenetics and Evolution, Journal of Vertebrate Paleontology et Journal of Systematic Palaeontology. Ce recensement a été effectué sur les fascicules publiés entre janvier 2010 et août 2012, sauf pour la revue Molecular Phylogenetics and Evolution dont l’étude a été restreinte aux mois de juillet, août et septembre 2012. Il ressort de ce comptage que les logiciels de parcimonie les plus employés à ce jour sont PAUP 4 (Swofford, 2002) et TNT (Goloboff et al., 2008). Afin de préciser leurs contextes d’utilisation, nous avons recherché et analysé dans un deuxième temps les articles citant l'un ou l'autre logiciel entre le 1er janvier 2010 et le 31 août 2012 sur la base de données bibliographiques Web of Science. Deux jeux de cartes scientométriques ont ensuite été réalisés à partir des termes employés dans les résumés des articles, et de leurs cooccurrences. Le premier permet de préciser le cadre d’utilisation de chaque programme et d’en montrer les spécificités. Le deuxième jeu construit à partir des termes retenus communs aux deux logiciels permet de comparer plus particulièrement leur emploi.
New insights on archaeal phylogeny
Session communications libres
Communication orale
Céline Petitjean, Equipe Génome, Evolution, Bioinformatique, Laboratoire de Chimie Bacterienne (CNRS - UPR9043), IFR88 - 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, FRANCE. E-mail : celine.petitjean@u-psud.fr
David Moreira, Purificación López-García, Equipe Diversité et évolution microbiennes, Laboratoire d'Ecologie, Systématique et Evolution - UMR CNRS 8079, Université Paris-Sud. Bâtiment 360, 91405 Orsay Cedex, FRANCE. E-mail: david.moreira@u-psud.fr, puri.lopez@u-psud.fr
Céline Brochier-Armanet, Laboratoire de Biométrie et Biologie Evolutive - UMR CNRS 5558, Université Lyon 1, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne, FRANCE. E-mail: celine.brochier-armanet@univ-lyon1.fr
Evolutionary history of Archaea, one of the three domains of life, remains partly unresolved, particularly in the relationships among phyla, and the branching position of poorly characterized groups. Recently, the symbolic threshold of one hundred complete archaeal genomes was crossed. At the same time, the last few years have witnessed a burst in genomic and metagenomic projects for poorly characterized groups or new lineages of high taxonomic rank (e.g. Nanohaloarchaea, Thaumarchaeota, ARMAN, ‘Aigarchaeota’, etc.). This provides unprecedented material to study the evolutionary history of the Archaea and expand our knowledge of their diversity.
Ribosomal proteins have been shown to be valuable phylogenetic markers to reconstruct the evolutionary history of Archaea and they are now used routinely to infer the phylogenetic position of newly sequenced archaeal lineages. However, despite their qualities as phylogenetic markers, archaeal phylogenies based on ribosomal proteins are not completely resolved, leaving important relationships unclear. The search for new phylogenetic markers is therefore crucial.
Based on the analysis of recent genomic data, we have identified more than 250 conserved proteins carrying a phylogenetic signal suitable to infer the global phylogeny of Archaea, especially the most ancient nodes. The analysis of this large dataset sheds a new light on the evolutionary history of the third Domain of Life.
« Disentangling the bindweeds: Systematics and Evolution of Merremieae (Convolvulaceae) »
Session communications libres
Communication orale
Ana R. Simões, NHM: Department of Botany, The Natural History Museum of London, Cromwell Road, London SW7, UK; University of Reading, Whiteknights, Reading, Berkshire, RG6 6AH, UK. Email: ana.simoes@nhm.ac.uk
Mark Carine , Department of Botany, The Natural History Museum of London, Cromwell Road, London SW7, UK.
Alastair Culham, The University of Reading, Whiteknights, Reading, Berkshire, RG6 6AH, UK
George Staples, Singapore Botanic Garden, 1 Cluny Road, 259569, Singapore
The tribe Merremieae has always challenged taxonomists and systematists working on the family Convolvulaceae. The lack of good morphological characters to delimit it and the increase in the number of published species in floristic accounts has turned the tribe into an aggregation of questionably related taxa. Recently published phylogenetic studies based on molecular data of Convolvulaceae have indicated that the tribe is not monophyletic, and that its largest genus Merremia Hall. f. is polyphyletic. The morphological variation in this tribe is overwhelming, even among characters that have been used for generic and tribal circumscription, such as pollen and fruit types. No taxonomic account exists for the tribe, nor for the genus Merremia, so a comprehensive revision of the Merremieae has been lacking to help get the taxonomy in order. The present study aims to investigate the evolutionary relationships in Merremieae, to study the evolution of its interestingly variable morphological traits, and ultimately to produce a taxonomic revision of the group. A thorough morphological survey of taxa from across the whole distribution range of the tribe has been undertaken and a large number of macromorphological, palynological and molecular characters have been used. In this presentation, our preliminary hypotheses of evolution of the Merremieae are discussed.
Global Variation and Evolution of Drought-Tolerance in Conifers
Poster
S. Delzon, INRA - University of Bordeaux, Talence, France. pujoulade@gmail.com
M. Larter, INRA - University of Bordeaux, Talence, France. maximilien.larter@gmail.com
The Pinales is one of the most ecologically and economically important plant Orders that exhibits order of magnitude variation in key functional traits spanning >250My of evolution. Of particular interest given their longevity and stature, is the evolution of stress tolerance in the water-transport system. Using the newly developed CAVITRON technique, an extensive dataset has been developed for cavitation resistance (P50, the pressure inducing 50% loss of hydraulic conductance), a fitness-related trait critical for plant survival during drought. We analyzed the global variation in cavitation resistance and related traits across 203 conifer species from the seven extant conifer families growing in the four main biomes. P50 varied widely across species and genera (from -2 to -16 MPa) and within all biomes, except in the boreal forest. Using a molecular phylogeny and several metrics, we find that convergent evolution for resistance to cavitation occurred in several lineages. In addition, much of the present day variation is found between the main clades within the Cupressaceae, whereas the Pinaceae exhibited a strong evolutionary stasis. There was no evidence for correlated evolution between hydraulic conductivity and P50, but a significant link between wood density and cavitation resistance in conifers suggests an evolutionary basis for a trade-off between safety and construction cost. These findings provide a global and integrative understanding of the macro-evolution and cross-species variation in a core fitness-related trait in conifers.
Mythes et réalités de la systématique : la dichotomie des arbres phylogénétiques
Session communications libres
Communication orale
René Zaragüeta, MNHN, UMR7207, CP48 (bat de géologie), 57 rue Cuvier, 75005 Paris. E-mail: Rene.Zaragueta_Bagils@upmc.fr
L’arbre enraciné et dichotomique est le modèle que la plupart des théories et méthodes phylogénétiques actuelles partagent : face à ce graphe particulier, tout systématicien identifie immédiatement un arbre phylogénétique mais se trouve dans l’incapacité à indiquer de quelle théorie et méthode cet arbre est le résultat ; c'est-à-dire qu'il est incapable d'expliciter de quelles informations et connaissances il est porteur. Le fait que des théories différentes (au mieux incommensurables, au pire incompatibles) aboutissent au même modèle est une particularité de la systématique. De plus, ces théories semblent souvent produire les mêmes résultats empiriques (plus de 99.5% des fois pour la parcimonie et le maximum de vraisemblance selon une étude récente), ce qui est une anomalie d’autant plus remarquable dans le domaine des sciences de la nature.
Le choix de l'arbre enraciné se justifie par la supposition que la vie a une origine unique ou par l'hypothèse, testable, sur l'existence d'une unique classification naturelle. Mais qu’est-ce qui justifie la dichotomie des arbres phylogénétiques ? Comme il est de bon ton d’affirmer que la recherche d’arbres phylogénétiques se fonde sur la descendance avec modification, les auteurs font généralement appel au processus évolutif : la spéciation serait un processus dichotomique. Or, quelle est la base empirique qui permet d’affirmer que le processus de spéciation est dichotomique ? Pourquoi « l’espèce ancestrale » doit-elle disparaître lorsque des « espèces descendantes » apparaissent ? Pourquoi la descendance avec modification doit-elle produire toujours deux, et uniquement deux, modifications dans la descendance ?
Je démontre ici que seule la théorie cladistique, dans son approche dite d’analyse à trois éléments, permet de justifier la dichotomie des arbres phylogénétiques. Elle n’est rien de plus que la conséquence de la méthode analytique appliquée à l’étude des relations de parenté entre taxons. Elle résulte de la structure même des relations d'homologie et des caractères, indiquant le degré d’identité entre homologues.
Finalement, je discute l’idée selon laquelle l’existence de transferts latéraux de gènes contredirait en partie le choix de cette structure, conduisant plutôt à une représentation par réseau des relations de parenté. Les défenseurs des réseaux les préfèrent aux arbres dichotomiques interprétés comme une lecture naïve d’un processus de spéciation dichotomique. Cependant, si la justification du choix des arbres dichotomiques ne découle pas de l'existence d'un processus dichotomique, la critique faisant appel aux transferts latéraux est infondée.
Simuler, c'est (parfois) tromper ? La MSM de Siddall et la question de ce qui est simulé
Session communications libres
René Zaragüeta, MNHN, UMR7207, CP48 (bat de géologie), 57 rue Cuvier, 75005 Paris. E-mail: Rene.Zaragueta_Bagils@upmc.fr
Dans les années 1990, furent proposées une série d'indices supposés mesurer la qualité des registres fossiles ou l'ajustement ou accord entre les arbres phylogénétiques et les datations stratigraphiques des âges d'origine des taxons. Siddall identifie un biais évident dans certains (la plupart) de ces indices et propose une nouvelle mesure, la Manhattan Stratigraphic Measure (MSM), censée être libre de ce biais. Pol et Norell précisent postérieurement que la MSM est l'IC d'un caractère d'âge ; de plus, ils montrent que le script fourni par Siddall pour calculer la MSM avec PAUP est défectueux. En 2004, Pol, Norell et Siddall publient une comparaison de certains des indices critiqués par Siddall à l'aide de simulations relativement complexes. Ces simulations semblent indiquer que, contrairement aux autres mesures testées, la MSM est libre des biais liés à la forme des arbres et à la taille de l'échantillonnage.
Je montre ici que, contrairement aux affirmations de Pol, Norell et Siddall, la MSM est non seulement biaisée, mais qu'elle l'est exactement de la même façon que les mesures que Siddall critique, c'est à dire par la forme des arbres. Ce biais est mis en évidence sans avoir recours à des simulations qui, contrairement aux affirmations de ces auteurs, semblent cacher la réalité plutôt que la clarifier.
J'utilise cet exemple pour poser une question plus générale concernant la pertinence des simulations en phylogénétique : comment peut-on effectuer des simulations censées pouvoir juger de la qualité relative de théories incommensurables, voire incompatibles ?
@SFS Société Française de Systématique
