Éditeur(s) : Public Library Science
Résumé : Biological invasions rank amongst the most deleterious components of global change inducing alterations from genes to ecosystems. The genetic characteristics of introduced pools of individuals greatly influence the capacity of introduced species to establish and expand. The recently demonstrated heritability of microbial communities associated to individual genotypes of primary producers makes them a potentially essential element of the evolution and adaptability of their hosts. Here, we characterized the bacterial communities associated to native and non-native populations of the marine green macroalga Caulerpa racemosa through pyrosequencing, and explored their potential role on the strikingly invasive trajectory of their host in the Mediterranean. The similarity of endophytic bacterial communities from the native Australian range and several Mediterranean locations confirmed the origin of invasion and revealed distinct communities associated to a second Mediterranean variety of C. racemosa long reported in the Mediterranean. Comparative analysis of these two groups demonstrated the stability of the composition of bacterial communities through the successive steps of introduction and invasion and suggested the vertical transmission of some major bacterial OTUs. Indirect inferences on the taxonomic identity and associated metabolism of bacterial lineages showed a striking consistency with sediment upheaval conditions associated to the expansion of their invasive host and to the decline of native species. These results demonstrate that bacterial communities can be an effective tracer of the origin of invasion and support their potential role in their eukaryotic host's adaptation to new environments. They put forward the critical need to consider the 'meta-organism' encompassing both the host and associated micro-organisms, to unravel the origins, causes and mechanisms underlying biological invasions.
Plos One (1932-6203) (Public Library Science), 2013-07 , Vol. 8 , N. 7 , P. -

Droits : 2013 Aires et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
http://archimer.ifremer.fr/doc/00157/26791/24886.pdf
DOI:10.1371/journal.pone.0068429
http://archimer.ifremer.fr/doc/00157/26791/

Éditeur(s) : HAL CCSD WILEY-BLACKWELL Wiley
Résumé : International audience
Connectivity among populations determines the dynamics and evolution of populations, and its assessment is essential in ecology in general and in conservation biology in particular. The robust basis of any ecological study is the accurate delimitation of evolutionary units, such as populations, metapopulations and species. Yet a disconnect still persists between the work of taxonomists describing species as working hypotheses and the use of species delimitation by molecular ecologists interested in describing patterns of gene flow. This problem is particularly acute in the marine environment where the inventory of biodiversity is relatively delayed, while for the past two decades, molecular studies have shown a high prevalence of cryptic species. In this study, we illustrate, based on marine case studies, how the failure to recognize boundaries of evolutionary-relevant unit leads to heavily biased estimates of connectivity. We review the conceptual framework within which species delimitation can be formalized as falsifiable hypotheses and show how connectivity studies can feed integrative taxonomic work and vice versa. Finally, we suggest strategies for spatial, temporal and phylogenetic sampling to reduce the probability of inadequately delimiting evolutionary units when engaging in connectivity studies.
ISSN: 0962-1083

hal-01218810
https://hal.archives-ouvertes.fr/hal-01218810
DOI : 10.1111/mec.13048

Éditeur(s) : Inter-Research
Résumé : The widespread use of Agent Orange (a mixture of phenoxyl herbicides) over Southern Vietnam by US Forces led to the decimation of mangrove forests in the Mekong Delta. Mangrove trees Avicennia alba were sampled across the Mekong Delta; their age was assessed using models based on internode growth and samples were genotyped for 6 microsatellite loci. The evolution of genetic diversity over time elapsed since local extinction was reconstructed and compared with the genetic diversity of an unaffected population from Thailand, The results show that genetic diversity of the A. alba population is still increasing in the Mekong Delta 3 decades after the end of the Vietnam War, but is reaching an asymptotic level that is comparable to the adjacent non-affected population of Thailand. This might be a sign of genetic recovery, but may also reveal a limitation, either of genetic enrichment due to current predominance of auto-recruitment or of demographic increase due to intraspecific competition in this pioneer species. In any case, these results, although encouraging, demonstrate that genetic recovery after complete or almost complete population depletion continues over a longer time-scale than apparent demographic recovery.
Marine Ecology Progress Series (0171-8630) (Inter-Research), 2009-09 , Vol. 390 , P. 129-135

Droits : Inter-Research 2009
http://archimer.ifremer.fr/doc/2009/publication-6898.pdf
DOI:10.3354/meps08183
http://archimer.ifremer.fr/doc/00000/6898/

Éditeur(s) : Wiley-blackwell Publishing, Inc
Résumé : Seagrasses structure some of the world's key coastal ecosystems presently in decline due to human activities and global change. The ability to cope with environmental changes and the possibilities for shifts in distribution range depend largely on their evolvability and dispersal potential. As large-scale data usually show strong genetic structure for seagrasses, finer-grained work is needed to understand the local processes of dispersal, recruitment and colonization that could explain the apparent lack of exchange across large distances. We aimed to assess the fine-grained genetic structure of one of the most important and widely distributed seagrasses, Zostera marina, from seven meadows in Brittany, France. Both classic population genetics and network analysis confirmed a pattern of spatial segregation of polymorphism at both regional and local scales. One location exhibiting exclusively the variety 'angustifolia' did not appear more differentiated than the others, but instead showed a central position in the network analysis, confirming the status of this variety as an ecotype. This phenotypic diversity and the high allelic richness at nine microsatellites (2.33-9.67 alleles/locus) compared to levels previously reported across the distribution range, points to Brittany as a centre of diversity for Z. marina at both genetic and phenotypic levels. Despite dispersal potential of several 100 m, a significant pattern of genetic differentiation, even at fine-grained scale, revealed 'genetic patchiness'. Meadows seem to be composed of a mosaic of clones with distinct origins in space and time, a result that calls into question the accuracy of the concept of populations for such partially clonal species.
Molecular Ecology (0962-1083) (Wiley-blackwell Publishing, Inc), 2010-06 , Vol. 19 , N. 12 , P. 2394-2407

Droits : 2010 Blackwell Publishing Ltd
http://archimer.ifremer.fr/doc/00006/11690/8499.pdf
DOI:10.1111/j.1365-294X.2010.04649.x
http://archimer.ifremer.fr/doc/00006/11690/

Éditeur(s) : Natl Acad Sciences
Résumé : The marine realm represents 70% of the surface of the biosphere and contains a rich variety of organisms, including more than 34 of the 36 living phyla, some of which are only found in the oceans. The number of marine species used by humans is growing at unprecedented rates, including the rapid domestication of marine species for aquaculture and the discovery of natural products and genes of medical and biotechnological interest in marine biota. The rapid growth in the human appropriation of marine genetic resources (MGRs), with over 18,000 natural products and 4,900 patents associated with genes of marine organisms, with the latter growing at 12% per year, demonstrates that the use of MGRs is no longer a vision but a growing source of biotechnological and business opportunities. The diversification of the use of marine living resources by humans calls for an urgent revision of the goals and policies of marine protected areas, to include the protection of MGRs and address emerging issues like biopiracy or benefit sharing. Specific challenges are the protection of these valuable resources in international waters, where no universally accepted legal framework exists to protect and regulate the exploitation of MGRs, and the unresolved issues on patenting components of marine life. Implementing steps toward the protection of MGRs is essential to ensure their sustainable use and to support the flow of future findings of medical and biotechnological interest.
Proceedings Of The National Academy Of Sciences Of The United States Of America (0027-8424) (Natl Acad Sciences), 2010-10 , Vol. 107 , N. 43 , P. 18318-18324

Droits : 2010 by the National Academy of Sciences
http://archimer.ifremer.fr/doc/00018/12897/9935.pdf
DOI:10.1073/pnas.0911897107
http://archimer.ifremer.fr/doc/00018/12897/

Éditeur(s) : Springer
Résumé : Pearl oysters belonging to the genus Pinctada (Bivalvia: Pteriidae) are widely distributed between the Indo-Pacific and western Atlantic. The existence of both widely distributed and more restricted species makes this group a suitable model to study diversification patterns and prevailing modes of speciation. Phylogenies of eight out of the 11 currently recognised Pinctada species using mitochondrial (cox1) and nuclear (18S rRNA) data yielded two monophyletic groups that correspond to shell size and presence/absence of hinge teeth. Character trace of these morphological characters onto the molecular phylogeny revealed a strong correlation. Pinctada margaritifera appears polyphyletic with specimens from Mauritius grouping in a different clade from others of the French Polynesia and Japan. Hence, P. margaritifera might represent a species complex, and specimens from Mauritius could represent a different species. Regarding the putative species complex Pinctada fucata/Pinctada martensii/Pinctada radiata/Pinctada imbricata, our molecular analyses question the taxonomic validity of the morphological characters used to discriminate P. fucata and P. martensii that exhibited the lowest genetic divergence and are most likely conspecific as they clustered together. P. radiata and P. imbricata were recovered as monophyletic. The absence of overlapping distributions between sister lineages and the observed isolation by distance suggests that allopatry is the prevailing speciation mode in Pinctada. Bayesian dating analysis indicated a Miocene origin for the genus, which is consistent with the fossil record. The northward movement of the Australian plate throughout the Miocene played an important role in the diversification process within Pinctada.
Marine Biotechnology (1436-2228) (Springer), 2011-04 , Vol. 13 , N. 2 , P. 181-192

Droits : Springer Science+Business Media, LLC 2010
http://archimer.ifremer.fr/doc/00035/14635/14015.pdf
DOI:10.1007/s10126-010-9278-y
http://archimer.ifremer.fr/doc/00035/14635/

Éditeur(s) : Elsevier
Résumé : The Latin American shrimp Litopenaeus stylirostris was introduced in three different Pacific islands (Tahiti, New Caledonia via Tahiti, and Hawaii) and hatchery-propagated for 7-25 generations to develop shrimp farming based on these domesticated stocks. Three microsatellite markers have been used in an attempt to assess the genetic bases of the populations available to start a selective breeding program. The comparison of eight hatchery stocks (five New Caledonian, two Hawaiian and one Tahitian stocks) and one wild Ecuadorian population showed a much lower variability in the domesticated stocks than in the wild population, especially in New Caledonia and Tahiti (2-3.7 vs. 14-27 alleles per locus; 20-60% vs. 90% expected heterozygosity). The Tahitian and the New Caledonian stocks share the same alleles, suggesting that the loss of alleles occurred during the common past of these populations. On the contrary, New Caledonian and Hawaiian populations share only one common allele at the three loci studied. Although the low genetic variability and the resulting inbreeding of the New Caledonian stocks do not seem to affect their present performance, the results of this study demonstrate the usefulness of the introduction of new stocks in order to increase the potential responses to new controlled or uncontrolled selective pressures. The introduction in New Caledonia of the Hawaiian domesticated stocks, which would provide the local shrimp industry with 40% of the allelic diversity of the species, is advised and preferred to the one of wild animals in order to take advantage (i) of the spontaneous selection which occurred during domestication and (ii) of their favourable sanitary "specific pathogen free" status (no presence of four viruses: WSV, YHV, IHHNV, TSV) which limits the risk of introduction of pathogens.
La crevette d'Amérique latine Litopaenus stylirostris a été introduite dans trois îles du Pacifique (à Tahiti, en Nouvelle-Calédonie via Tahiti, et à Hawaii), et a été ensuite reproduite en écloserie pendant 7 à 25 générations à des fins d'aquaculture. Trois marqueurs microsatellites ont été utilisés pour évaluer les bases génétiques des populations disponibles pour le démarrage d'un programme d'amélioration génétique. L'étude comparative de 8 populations domestiquées (cinq néo-calédoniennes, deux hawaiiennes et une tahitienne) et d'une population sauvage d'Equateur révèle une variabilité très réduite dans les populations d'élevage, en particulier en Nouvelle-Calédonie et à Tahiti (2 à 3.7 allèles par locus au lieu de 14 à 27 en population sauvage ; 20% à 60% d'hétérozygotie au lieu de 90%). Les souches tahitiennes et calédoniennes disposent des mêmes allèles, ce qui suggère que la perte d'allèles a eu lieu lors de l'histoire commune des ces populations. A l'inverse, les populations néo-calédoniennes et hawaiiennes n'ont en commun qu'un seul allèle sur les 3 locus étudiés. Bien que la très faible variabilité génétique du cheptel calédonien ne semble pas affecter ses performances actuelles, les résultats de cette étude démontrent l'utilité de l'introduction de variabilité afin d'augmenter la capacité de réponse à de nouvelles pressions de sélection (contrôlées ou non). L'introduction des souches hawaiiennes en Nouvelle-Calédonie qui permettrait à la filière locale de disposer de 40% de la diversité allélique de l'espèce) est préconisée de préférence à celle d'animaux sauvages afin de bénéficier (i) de la sélection spontanée qu'elles ont subi lors de leur domestication et (ii) de leur statut sanitaire « specific pathogen free, SPF » (absence de 4 virus : WSV, YHV, IHHNV, TSV) qui limite les risques de transferts de pathogènes.
Aquatic Living Resources (0990-7440) (Elsevier), 2003-12 , Vol. 16 , N. 6 , P. 501-508

Droits : 2003 Published by Elsevier, Paris.
http://archimer.ifremer.fr/doc/2003/publication-596.pdf
DOI:10.1016/j.aquliv.2003.07.001
http://archimer.ifremer.fr/doc/00000/596/

Éditeur(s) : Wiley-blackwell
Résumé : In bird species that have a high movement capacity, dispersal may connect subpopulations over vast geographical regions, with important consequences for the design of conservation management strategies. Here we used a molecular approach to infer the patterns and rates of dispersal among eight Mediterranean subpopulations of the endangered Bonelli's Eagle, based on 245 individuals screened at 17 microsatellite loci. There was moderate genetic differentiation between subpopulations sampled in the western (Iberia and Morocco) and eastern (Cyprus) Mediterranean, whereas differentiation among subpopulations in the former region was weak to moderate and followed a pattern of isolation by distance. Within the western Mediterranean, the small, peripheral and ecologically unique population of southwest Portugal had the lowest genetic diversity and the highest differentiation. The remaining subpopulations formed two loose clusters, one including Morocco and southwest and eastern Spain, and the other northeast Portugal and western and central Spain. Few recent migrants were detected, and they originated primarily from adjacent subpopulations. Our findings suggest that western Mediterranean Bonelli's Eagles may have a large-scale metapopulation structure, with subpopulations connected to some extent by distance-dependent dispersal, probably influenced by natal philopatry and the geographical configuration of subpopulations. The combination of marked ecological and genetic divergence suggests that the peripheral subpopulation of southwest Portugal may be regarded as a distinct management unit.
Ibis (0019-1019) (Wiley-blackwell), 2013-07 , Vol. 155 , N. 3 , P. 485-498

Droits : 2013 British Ornithologists’ Union
http://archimer.ifremer.fr/doc/00148/25924/24018.pdf
DOI:10.1111/ibi.12065
http://archimer.ifremer.fr/doc/00148/25924/

Éditeur(s) : Wiley-blackwell
Résumé : The history of colonization and dispersal in fauna distributed among deep-sea chemosynthetic ecosystems remains enigmatic and poorly understood because of an inability to mark and track individuals. A combination of molecular, morphological and environmental data improves understanding of spatial and temporal scales at which panmixia, disruption of gene flow or even speciation may occur. Vestimentiferan tubeworms of the genus Escarpia are important components of deep -sea cold seep ecosystems, as they provide long-term habitat for many other taxa. Three species of Escarpia, Escarpia spicata [Gulf of California (GoC)], Escarpia laminata [Gulf of Mexico (GoM)] and Escarpia southwardae (West African Cold Seeps), have been described based on morphology, but are not discriminated through the use of mitochondrial markers (cytochrome oxidase subunit 1; large ribosomal subunit rDNA, 16S; cytochrome b). Here, we also sequenced the exon-primed intron-crossing Haemoglobin subunit B2 intron and genotyped 28 microsatellites to (i) determine the level of genetic differentiation, if any, among the three geographically separated entities and (ii) identify possible population structure at the regional scale within the GoM and West Africa. Results at the global scale support the occurrence of three genetically distinct groups. At the regional scale among eight sampling sites of E. laminata (n=129) and among three sampling sites of E. southwardae (n=80), no population structure was detected. These findings suggest that despite the patchiness and isolation of seep habitats, connectivity is high on regional scales.
Molecular Ecology (0962-1083) (Wiley-blackwell), 2013-08 , Vol. 22 , N. 16 , P. 4147-4162

Droits : 2013 John Wiley & Sons Ltd
http://archimer.ifremer.fr/doc/00152/26354/24515.pdf
DOI:10.1111/mec.12379
http://archimer.ifremer.fr/doc/00152/26354/

Éditeur(s) : Springer
Résumé : Clonality and genetic structure of the coral Pocillopora damicornis sensu lato were assessed using five microsatellites in 12 populations from four islands of the Society Archipelago (French Polynesia) sampled in June 2008. The 427 analysed specimens fell into 132 multilocus genotypes (MLGs), suggesting that asexual reproduction plays an important role in the maintenance of these populations. A haploweb analysis of ITS2 sequences of each MLG was consistent with all of them being conspecific. Genetic differentiation was detected both between and within islands, but when a single sample per MLG was included in the analyses, the populations turned out to be nearly panmictic. These observations provide further evidence of the marked variability in reproductive strategies and genetic structure of P. damicornis throughout its geographic range; comparison with results previously obtained for the congeneric species Pocillopora meandrina underlines the importance of life history traits in shaping the genetic structure of coral populations
Marine Biology (0025-3162) (Springer), 2014-03 , Vol. 161 , N. 3 , P. 531-541

Droits : Springer-Verlag Berlin Heidelberg 2013
http://archimer.ifremer.fr/doc/00171/28209/26518.pdf
DOI:10.1007/s00227-013-2355-9
http://archimer.ifremer.fr/doc/00171/28209/