Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Determining the conditions under which populations may persist requires accurate estimates of demographic parameters, including immigration, local reproductive success, and mortality rates. In marine populations, empirical estimates of these parameters are rare, due at least in part to the pelagic dispersal stage common to most marine organisms. Here, we evaluate population persistence and turnover for a population of orange clownfish, Amphiprion percula, at Kimbe Island in Papua New Guinea. All fish in the population were sampled and genotyped on five occasions at 2-year intervals spanning eight years. The genetic data enabled estimates of reproductive success retained in the same population (reproductive success to self-recruitment), reproductive success exported to other subpopulations (reproductive success to local connectivity), and immigration and mortality rates of sub-adults and adults. Approximately 50% of the recruits were assigned to parents from the Kimbe Island population and this was stable through the sampling period. Stability in the proportion of local and immigrant settlers is likely due to: low annual mortality rates and stable egg production rates, and the short larval stages and sensory capacities of reef fish larvae. Biannual mortality rates ranged from 0.09 to 0.55 and varied significantly spatially. We used these data to parametrize a model that estimated the probability of the Kimbe Island population persisting in the absence of immigration. The Kimbe Island population was found to persist without significant immigration. Model results suggest the island population persists because the largest of the subpopulations are maintained due to having low mortality and high self-recruitment rates. Our results enable managers to appropriately target and scale actions to maximize persistence likelihood as disturbance frequencies increase.
ISSN: 0962-8452

hal-01239322
https://hal-univ-perp.archives-ouvertes.fr/hal-01239322
DOI : 10.1098/rspb.2015.1311

Éditeur(s) : Actes du 6e colloque national BRG, La Rochelle, 2-3-4 octobre 2006
Résumé : Previous studies have shown heritable variation in larval developmental traits in the Pacific oyster Crassostrea gigas. In order to study the genetic consequences of production of oyster larvae in hatcheries, two factors, specific to hatcheries, were examined: the effect of discarding the smallest larvae (i.e. culling) and the effect of temperature (20°C versus 26°C). A mixed-family approach was used in order to infer the genetic composition of larval populations and family assignment, limiting possible environmental bias and allowing the study of a relatively large number of families using a limited number of larval tanks. Our results show that three multiplexed highly polymorphic microsatellite markers are a powerful tool for family assignment and, consequently, for the study of bivalve larvae genetics. Culling, by selective sieving of the smallest larvae is an advantageous practice at a phenotypic scale as it reduced variance in larval size, variance of developmental rate and time to settlement. Culling of 50% of the larval population only led to 15% less spat, showing a positive phenotypic correlation between larval growth and settlement success. However, culling represents a substantial risk for diversity loss, because it increases the variance of reproductive success among parental oysters. The effective population sizes of early settling cohorts of settlement were lower than those of later ones. Our results show that the settlement of slow growing larvae significantly contributes to minimizing the variability of reproductive success and therefore to maximizing genetic diversity. These results corroborate the low estimations of variability of broodstocks sampled in several French commercial hatcheries, relative to natural populations. The genetic composition of the larval population and the resulting spat was significantly different between the two tested temperatures, revealing genotype x environment interaction for survival. Similarly, genotype x environment interaction was also observed for larval growth as a higher temperature exerted a positive influence on the expression of genetic variability for this trait. Consequently, we can conclude that a temperature of 26°C coupled with culling, to common practice in oyster hatcheries, is likely to amplify the selection pressure for fast growing larvae. To test for this hypothesis, we compared larval developmental traits in the progeny of a hatchery broodstock closed for 7 generations, with the progeny of wild oysters and the two possible hybrids. Our results show that selection of fast growing larvae can counteract presumed inbreeding depression, due to higher mean relatedness among hatchery broodstock than in the wild. Genetic effects of intensive rearing conditions at larval stage are significant and should be taken into account in hatchery practices, especially in terms of genetic diversity management.
Afin d'étudier les conséquences génétiques des pratiques de production en écloserie d'huître creuse, deux facteurs ont été examinés : l'élimination des petites larves et la température. Nos résultats montrent que l'assignation de parenté par marqueurs microsatellites est un outil performant pour les études génétiques en phase larvaire de familles élevées en mélange. Bien qu'avantageux d'un point de vue phénotypique, le tamisage sélectif représente un risque de perte de diversité. La fixation des larves à croissance lente permet en effet de minimiser la variabilité du succès reproducteur et de fait, de maximiser la variabilité génétique. Ces résultats corroborent les estimations de variabilité sur les stocks d'écloseries françaises où l'on constate une diversité allélique inférieure à celle de populations issues du milieu naturel. La température exerce également une influence sur la précocité de l'expression de la variabilité génétique pour la croissance larvaire. Ainsi une température élevée associée à une procédure de tamisage peut amplifier l'effet sélectif. Enfin, la sélection de larves à croissance rapide semble démontrée, s'opposant à la dépression de consanguinité présumée. Les conditions d'élevage peuvent donc avoir un effet génétique significatif qui devrait être pris en considération dans les pratiques d'écloserie, notamment dans la gestion de la diversité génétique.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/acte-1505.pdf
http://archimer.ifremer.fr/doc/00000/1505/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Tree mortality in tropical forests is a complex ecological process for which modelling approaches need to be improved to better understand, and then predict, the evolution of tree mortality in response to global change. The mortality model introduced here computes an individual probability of dying for each tree in a community. The mortality model uses the ontogenetic stage of the tree because youngest and oldest trees are more likely to die. Functional traits are integrated as proxies of the ecological strategies of the trees to permit generalization among all species in the community. Data used to parametrize the model were collected at Paracou study site, a tropical rain forest in French Guiana, where 20,408 trees have been censused for 18 years. A Bayesian framework was used to select useful covariates and to estimate the model parameters. This framework was developed to deal with sources of uncertainty, including the complexity of the mortality process itself and the field data, especially historical data for which taxonomic determinations were uncertain. Uncertainty about the functional traits was also considered, to maximize the information they contain. Four functional traits were strong predictors of tree mortality: wood density, maximum height, laminar toughness and stem and branch orientation, which together distinguished the light-demanding, fast-growing trees from slow-growing trees with lower mortality rates. Our modelling approach formalizes a complex ecological problem and offers a relevant mathematical framework for tropical ecologists to process similar uncertain data at the community level.
ISSN: 1932-6203

hal-01190561
https://hal.archives-ouvertes.fr/hal-01190561
PRODINRA : 208582
PUBMED : 23675500
DOI : 10.1371/journal.pone.0063678

Éditeur(s) : HAL CCSD
Résumé : International audience
Calculation of seismic risks in a zone are based on stochastic models describing at best the seismic activity. Our focus is the spatio-temporal evolution of the probability of earthquake occurrences. The main modelling tool is the theory of the point processes. We discuss about the spatio-temporal extension of ETAS (Epidemic Type Aftershock Sequence) with marks and study the properties of the log-likelihood and the maximum likelihood estimators. Seismic data from the Lesser Antilles Arc carried out between 1999 and 2004 are analyzed.
39th Annual Meeting of the Statistical Society of Canada
Wolfville, Canada

hal-00601513
https://hal.archives-ouvertes.fr/hal-00601513

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Orogenic lherzolites exhibit a specific (although reproducible) platinum-group element signature characterized by slight positive deviations of Pd/Ir, Rh/Ir and Ru/Ir ratios from the canonical chondritic model. Such a signature was alternatively considered to be a compositional feature of the primitive upper mantle or resulting from sulfide melt addition by refertilisation reactions in the continental lithosphere. To shed additional light on this conundrum, the distribution of PGE in FON B 93, an unserpentinized, fertile (3.24% Al2O3) orogenic lherzolite (French Pyrenees) used as in-house standard by our group, has been studied to different scales, from the bulk rock to trace minerals. In addition to new ICPMS analyses after separation into Nis and Te coprecipitation, its whole-rock PGE concentrations were redetermined by three different laboratories using very precise ID-ICP-MS methods after digestion of the sample in Carius tube at T=250 degrees C and 320 degrees C or in high-pressure asher (HPA-S). The four methods produce reproducible Ru, Rh and Pd contents (7.1 +/- 0.18 ppb; 1.43 +/- 0.05 ppb; 7.1 +/- 0.30 ppb) whereas the non-ID NiS-fire assay method underestimates the Os and Ir concentrations by c.a. 10 and 15% compared to ID-ICP-MS analyses (4.40 +/- 0.07 and 4.00 +/- 0.17 ppb, respectively). Platinum was the most difficult to analyse. If performed on powder aliquots smaller than 3 g, the ID-ICP-MS analyses generate strong nugget effects while the non-ID NiS-fire assay method yields statistically lower (but highly reproducible) Pt concentrations (6.92 +/- 0.26 ppb). These features reflect the strong partitioning of Pt into trace phases that SEM and laser ablation-ICP-MS analyses on thin sections identify as both high-temperature Pt-Ir-Os alloys and Pt-(Pd) tellurides of likely subsolidus origin; ten to fifteen grains ranging in maximum dimension from a few micrometres to a few hundreds of nanometers, were identified by standard polished thin section. LA-ICP-MS data on base metal sulfides (25 grains analysed), coupled with the whole-rock S concentration (277 +/- 10 ppm) and modal composition of the BMS (90% pentlandite+accessory pyrite and secondary pyrrhotite + 10% chalcopyrite) allowed the contribution of the BMS phase to the PGE budget of FON B 93 to be estimated. Except Pt that exhibits a 95% deficit in the BMS phase, the PGE concentrations measured by ID-ICP-MS can be balanced by BMS while Al-spinel is a negligible contributor, accounting for less than 0.5% of the Ru budget. The occurrence of Pt in trace phases may bias the whole-rock Pt concentrations because 1) mechanical collection of Pt-rich trace phases remains problematic with the Nis button, and 2) Pt-Ir-Os alloys may be prone to digestion problems in conventional Carius tube procedures. Since they could be stable at mantle depth, such refractory alloys that contain Os and Ir may also have enhanced the heavy PGEs/light PGEs fractionation. Our observations likely pertain to orogenic lherzolites as a whole because BMS assemblages in these mantle rocks record evolution at low sulfur fugacity, which prevents Pt-Ir-Os alloy from entering the Mss in the mantle; moreover, at subsolidus temperature, pentlandite, the major BMS, cannot accommodate 0 valence state Pt.
ISSN: 0009-2541

hal-00411486
https://hal.archives-ouvertes.fr/hal-00411486
DOI : 10.1016/j.chemgeo.2007.06.030

Éditeur(s) : NRC
Résumé : We studied relationships between tropical tunas (albacore (Thunnus alalunga), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares)) and their biotic and abiotic environments through simultaneous acoustic observations of tunas and their prey, experimental longline catch, and oceanographic data in French Polynesia. Vertical habitat limits were estimated based on temperature and dissolved oxygen at capture data. We then studied tuna-micronekton relationships to better understand how tuna occupy the pelagic space, At a regional scale, tunas were more abundant in areas rich in prey with favourable hydrological conditions. Inside such areas, at the scale of a longline set, however, the longline catches were maximal only when prey were not distributed in dense patches (except for yellowfin tuna). We interpreted this result by considering that areas with high prey abundance attract tunas, but at a small scale, if prey are patchy distributed, tunas are more inclined to feed on them rather than on longline baits. The effect of patches on yellowfin tuna catch per unit effort (CPUE) does not appear likely because this species also feeds on the mixed layer, where patch density was very low. Not only hydrological characteristics, but also prey density and prey patch characteristics, should be taken into account for interpreting longline CPUE data.
Thunnus obesus, et thon à nageoires jaunes, Thunnus albacares) à leurs environnements biotique et abiotique. Pour ce faire, nous avons réalisé simultanément, en Polynésie Française, des observations acoustiques des thons et de leurs proies, des pêches à l'aide d'une palangre instrumentée et des mesures hydrologiques. Des limites d'habitat vertical des thons calculées sur la base de données de température et d'oxygène dissous sont proposées. Nous étudions ensuite les relations thons-micronecton afin de mieux comprendre la stratégie d'occupation de l'espace des thons. A une échelle régionale, les thons sont plus abondants dans des zones riches en proies avec des conditions hydrologiques favorables. Cependant, à l'intérieur de telles zones, les captures sont maximales lorsque les proies ne sont pas distribuées sous forme de patchs (sauf pour le thon à nageoires jaunes). Nous interprétons ces résultats en considérant que les zones de fortes abondances en proies attirent les thons mais, qu'à une échelle fine, si les proies sont distribuées sous la forme de patchs denses, les thons s'en nourrissent préférentiellement, au détriment des appâts de la palangre. Ces patchs ne semblent pas influencer les prises par unité d'effort (PUE) des thons à nageoires jaunes, probablement parce que cette espèce se nourrit également dans la couche homogène où la densité en patchs est très faible. Les caractéristiques hydrologiques, mais également la densité en proies et leur type de distribution, devraient donc être pris en compte pour l'interprétation des données de PUE.
Canadian journal of fisheries and aquatic sciences (0706-652X) (NRC), 2002-06 , Vol. 59 , N. 6 , P. 1002-1013

Droits : 2002 NRC Canada
http://archimer.ifremer.fr/doc/2002/publication-733.pdf
DOI:10.1139/F02-073
http://archimer.ifremer.fr/doc/00000/733/

Éditeur(s) : American Geophysical Union
Résumé : The origins and fates of the Atlantic salinity maximum water (SMW), formed through excess evaporation in the tropics and subtropics of both hemispheres, are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation. After defining formation domains from the surface salinity field and the vertical stratification, a Lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell. Formation rates around 9 and 11 Sv are found in the Southern and Northern Hemispheres, respectively. While the export of the southern SMW from its formation area is realized by the western boundary currents, that of the northern SMW mainly results from interior subduction. Equatorward of the formation regions, a fraction of each SMW variety is entrained in the subtropical cells that connect the subtropics to the equatorial region. Poleward of them, both varieties are seen to feed the regions of subtropical mode water (STMW) formation around 35degrees of latitude in both hemispheres. The bulk of the transport associated with each variety eventually turns northward: This amounts to similar to6 Sv of southern SMW gathered in the North Brazil Undercurrent (NBUC), and similar to10 Sv of northern SMW found in the Gulf Stream at 35degreesN, of which 8 Sv have gone through the Caribbean Sea. Of the 13.4-Sv northward transport of the meridional overturning cell estimated by the model at 47degreesN, more than 50% (6.9 Sv) is found to have transited through at least one of the SMW regions. This gives an indication of the likely important role of SMW formation in the observed northward salinity increase of the upper Atlantic Ocean.
Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2002-09 , Vol. 107 , N. C10 , P. NIL_610-NIL_624

Droits : 2002 by the American Geophysical Union
http://archimer.ifremer.fr/doc/2002/publication-769.pdf
DOI:10.1029/2002JC001318
http://archimer.ifremer.fr/doc/00000/769/

Éditeur(s) : HAL CCSD Wiley
Résumé : Outcrossing rates, pollen dispersal and male mating success were assessed in Dicorynia guianensis Amshoff, a neotropical tree endemic to the Guiana shield. All adult trees within a continuous area of 40 ha (n = 157) were mapped, and were genotyped with six microsatellite loci. In addition, progenies were genotyped from 22 mature trees. At the population level, the species was mostly outcrossing (tm = 0.89) but there was marked variation among individuals. One tree exhibited mixed mating, confirming earlier results obtained with isozymes that D. guianensis can tolerate selfing. A Bayesian extension of the fractional paternity method was used for paternity analysis, and was compared with the neighbourhood method used widely for forest trees. Both methods indicated that pollen dispersal was only weakly related to distance between trees within the study area, and that the majority (62%) of pollen came from outside the study stand. Using maximum likelihood, male potential population size was estimated to be 1119, corresponding to a neighbourhood size of 560 hectares. Male mating success was, however, related to the diameter of the stem and to flowering intensity assessed visually. The mating behaviour of D. guianensis is a combination of long-distance pollen flow and occasional selfing. The species can still reproduce when it is extremely rare, either by selfing or by dispersing pollen at long distances. These results, together with the observation that male mating success was correlated with the size of the trees, could be implemented in management procedures aiming at regenerating the species
ISSN: 0962-1083

hal-01032227
https://hal.archives-ouvertes.fr/hal-01032227
DOI : 10.1111/j.1365-294X.2004.02127.x