Éditeur(s) : Inter-research
Résumé : Mixed beds of Ophiocomina nigra and Ophiothrix fragilis (Echinodermata, Ophiuroidea) are usually predominated by O. fragilis and are reported to be stable over time. The Bay of Brest (Brittany, France) is a highly productive ecosystem where both species co-occur in the main central part. Using a geostatistical approach, we tested for changes in O. nigra and O. fragilis density and total biomass patterns between 1987 and 2011. Our results highlighted an increase in O. nigra population size and the induction of a spatial shift of the co-occurring O. fragilis. O. nigra increased similar to 5 times in density and covered almost all the study area, while its density-dependent biomass increased similar to 3 times (22 t km(-2), ash-free dry mass) between 1987 and 2011. Overall, the O. fragilis population decreased in density by similar to 30%, but its total biomass did not change over time. The current distribution pattern revealed a clear spatial exclusion of O. fragilis from the central part of the study area toward the southern part, overlapping beds of dead slipper limpet Crepidula fornicata, which were formerly considered to be the dominant suspension-feeder species in the bay. The success of O. nigra colonization is linked to its biological and functional traits, as well as deep changes in food supply over the studied period. Ecological consequences of such a large change in the benthic compartment of the bay are explored in the light of associated changes in environmental patterns.
Marine Ecology-progress Series (0171-8630) (Inter-research), 2012 , Vol. 460 , P. 79-90

Droits : 2012 Inter-Research
http://archimer.ifremer.fr/doc/00090/20136/17782.pdf
DOI:10.3354/meps09784
http://archimer.ifremer.fr/doc/00090/20136/

Éditeur(s) : HAL CCSD Western Indian Ocean Marine Science Association
Résumé : International audience
Juan de Nova is one of the scattered islands known as Iles Eparses in the Mozambique Channel (Western Indian Ocean). Historically, they have been isolated from many anthropogenic influences which makes them ideal areas to study biodiversity for comparison with areas that are heavily impacted by urbanization and fishing. The programme BioReCie (Biodiversity, Resources and Conservation of Eparses Islands) undertook inventories of several marine groups, including echinoderms, which had hitherto not been assessed in Juan de Nova. A multidisciplinary team surveyed the reef slopes of the island using SCUBA to a depth of 25 m as well as the reef flats at low tide, collecting specimens and taking photos for identification. Sixty echinoderm species were found, with 51 occurring on the reef flats and in the lagoon and 22 on the reef slopes, comprising 21 species of Holothuroidea, 16 Ophiuroidea, 10 Echinoidea, 7 Asteroidea, and 6 Crinoidea. Commercial species of Holothuroidea, some of which are classified as endangered in the IUCN red list, i.e. Thelenota ananas and Holothuria nobilis, were present on the reef flats, reef slopes and in the lagoon of the island, indicating the value that protection has on biodiversity.
ISSN: 0856-860X

hal-01306709
http://hal.univ-reunion.fr/hal-01306709
http://hal.univ-reunion.fr/hal-01306709/document
http://hal.univ-reunion.fr/hal-01306709/file/A%20First%20Inventory%20of%20Echinodermata%20at%20Juan%20de%20Nova_hal.pdf

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
AimThe global biodiversity crisis requires the identification of regions with high evolutionary potential, i.e. evolutionary hotspots (evospots). We created an analytical framework based on comparative phylogeography and coalescent methods to assess the dynamics of diversification and population persistence in the reef ecosystem of a little-studied region: the Southwestern Indian Ocean (SWIO).LocationCoral reefs of the SWIO, with comparative data from the Pacific Ocean.MethodsWe generated sequences of mitochondrial DNA (COI and 16S) for 10 widespread brittle-stars (345 specimens) from 21 localities (8 in the SWIO). We analysed them by combining comparative phylogeography approaches, coalescent-based methods, molecular clocks and the concept of evolutionarily significant units (ESUs) to draw conclusions about the drivers of biodiversity in the region.ResultsCryptic diversity was prevalent, increasing lineage diversity within the 10 nominal species by 70% within the SWIO and by 200% across the Indo-West Pacific. All seven new SWIO lineages meet the criteria for ESUs and at least six are biological species. We detected likely intraregional diversifications dating to the Plio-Pleistocene, supporting the SWIO as a generator of biodiversity. Geographical restriction of ESUs, long coalescent times (> 80 ka) and old in situ diversification (> 1 Ma) point to the persistence of populations over multiple glacio-eustatic cycles. We provide data suggesting demographic expansion during sea-level high stands. Regional connectivity was lower, and cryptic differentiation higher in lecithotrophs than in planktotrophs.Main conclusionsThe analytical framework based on a biodiversity survey makes it possible to identify evospots by assessing the potential of a region to maintain and generate biodiversity and by evaluating the evolutionary processes and potential drivers at play.
ISSN: 0305-0270

hal-01369697
http://hal.univ-reunion.fr/hal-01369697
DOI : 10.1111/jbi.12155