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) : 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/