Éditeur(s) : EDP Sciences
Résumé : A population of the invasive slipper limpet (Crepidula fornicata) has been spreading in the Bay of Mont-Saint-Michel (Western English Channel) for 40 years. Sidescan sonar, underwater video and quantitative sampling were conducted in 1996 and 2004 to document the widening geographic spread of the species over the bay. The limpet population grew by 50% during this period, to reach a fresh biomass of about 150 000 t. This local study analyses causes and effects of the spread and provides a typical example of the limpet spreading process. This population increase has significant effects on the environment in the most densely colonized area (modification to the sediment and biodiversity), leading to the emergence of a new benthic community. Anthropic dredging activities are among the causative factors of the spread but are also adversely affected by the invasion.
Depuis 40 ans, la population de crépidules (Crepidula fornicata) prolifère en baie du Mont Saint-Michel (Manche Ouest). Deux études réalisées en 1996 et 2004 ont permis de cartographier et d'estimer le stock de la population grâce à des moyens similaires : sonar à balayage latéral, vidéo sous-marine et prélèvements quantitatifs à la benne. Durant cet intervalle de temps, la biomasse a augmenté de 50 % pour atteindre 150 000 t dans la baie en 2004. Cette étude comparative a permis d'analyser les causes et les effets d'une telle prolifération et d'en montrer le processus général. Dans les secteurs fortement colonisés, les effets sur l'environnement sont particulièrement néfastes (modification du sédiment et de la biodiversité) et aboutissent à une nouvelle communauté benthique. Les activités de pêche aux engins traînants (dragues et chaluts) sont à la fois les principales responsables et les victimes de cette prolifération.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2009 , Vol. 22 , N. 1 , P. 11-19

Droits : 2009 EDP Sciences
http://archimer.ifremer.fr/doc/2009/publication-6351.pdf
DOI:10.1051/alr/2009004
http://archimer.ifremer.fr/doc/00000/6351/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : Nucleotide diversity was assessed within nine candidate genes (in total 4.6 kb) for the time of bud burst in nine sessile oak (Quercus petraea) populations distributed in central and northern Europe. The sampled populations were selected on the basis of their contrasting time of bud burst observed in common garden experiments (provenance tests). The candidate genes were selected according to their expression profiles during the transition from quiescent to developing buds and/or their functional role in model plants. The overall nucleotide diversity was large (pi(tot) - 6.15 x 10(-3); pi(silent) - 11.2 x 10(-3)), but population differentiation was not larger than for microsatellites. No outlier single-nucleotide polymorphism (SNP), departing from neutral expectation, was found among the total of 125 SNPs. These results contrasted markedly with the significant associations that were observed between the candidate genes and bud burst in segregating populations. Quantitative trait loci (QTLs) for bud burst were identified for 13 year*site seasonal observations in a cloned mapping pedigree. Nineteen QTLs were detected, and QTLs located on linkage groups 2, 5 and 9 contributed repeatedly to more than 12% of the phenotypic variation of the trait. Eight genes were polymorphic in the two parents of the pedigree and could be mapped on the existing genetic map. Five of them located within the confidence intervals of QTLs for bud burst. Interestingly, four of them located within the three QTLs exhibiting the largest contributions to bud burst.
ISSN: 0018-067X

hal-01032156
https://hal.archives-ouvertes.fr/hal-01032156
DOI : 10.1038/hdy.2009.170