Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
Most eukaryotic organisms are arthropods. Yet, their diversity in rich terrestrial ecosystems is still unknown. Here we produce tangible estimates of the total species richness of arthropods in a tropical rainforest. Using a comprehensive range of structured protocols, we sampled the phylogenetic breadth of arthropod taxa from the soil to the forest canopy in the San Lorenzo forest, Panama. We collected 6144 arthropod species from 0.48 hectare and extrapolated total species richness to larger areas on the basis of competing models. The whole 6000-hectare forest reserve most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of the arthropod biodiversity held in the wider landscape. Models based on plant diversity fitted the accumulated species richness of both herbivore and nonherbivore taxa exceptionally well. This lends credence to global estimates of arthropod biodiversity developed from plant models.
ISSN: 0036-8075

hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285/document
https://hal.archives-ouvertes.fr/hal-00817285/file/1226727Revisedtext.pdf
DOI : 10.1126/science.1226727

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
This article documents several cases of widespread species, which usually mimic other widespread species throughout the Indo–Pacific, using endemic Marquesan species as a model and displaying endemic mimicry patterns. This discovery adds a new line of evidence to the uniqueness of the Marquesas Islands, which not only host a high number of endemic reef–fish species, but also endemic mimicry patterns.
ISSN: 0022-1112

hal-01338324
http://hal.upmc.fr/hal-01338324
http://hal.upmc.fr/hal-01338324/document
http://hal.upmc.fr/hal-01338324/file/2016_Delrieu%E2%80%90Trottin%20et%20al_When%20endemic.pdf
DOI : 10.1111/jfb.13050

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The Black Rat (Rattus rattus) spread out of Asia to become one of the world's worst agricultural and urban pests, and a reservoir or vector of numerous zoonotic diseases, including the devastating plague. Despite the global scale and inestimable cost of their impacts on both human livelihoods and natural ecosystems, little is known of the global genetic diversity of Black Rats, the timing and directions of their historical dispersals, and the risks associated with contemporary movements. We surveyed mitochondrial DNA of Black Rats collected across their global range as a first step towards obtaining an historical genetic perspective on this socioeconomically important group of rodents. We found a strong phylogeographic pattern with well-differentiated lineages of Black Rats native to South Asia, the Himalayan region, southern Indochina, and northern Indochina to East Asia, and a diversification that probably commenced in the early Middle Pleistocene. We also identified two other currently recognised species of Rattus as potential derivatives of a paraphyletic R.rattus. Three of the four phylogenetic lineage units within R. rattus show clear genetic signatures of major population expansion in prehistoric times, and the distribution of particular haplogroups mirrors archaeologically and historically documented patterns of human dispersal and trade. Commensalism clearly arose multiple times in R. Rattus and in widely separated geographic regions, and this may account for apparent regionalism in their associated pathogens. Our findings represent an important step towards deeper understanding the complex and influential relationship that has developed between Black Rats and humans, and invite a thorough re-examination of host-pathogen associations among Black Rats.
PLoS ONE

ird-00714383
http://hal.ird.fr/ird-00714383
http://hal.ird.fr/ird-00714383/document
DOI : 10.1371/journal.pone.0026357
IRD : fdi:010055548

Éditeur(s) : HAL CCSD Luís Felipe Toledo
Résumé : International audience
Expedition Pakaihi I Te Moana was conducted in 2011 to the Marquesas Islands, lying between 07°50ʹ S and 10°35ʹ S latitude and 138°25ʹ W and 140°50ʹ W longitude. The expedition combined extensive collections and visual censuses of the shore fish fauna. A total of 74 species are added as new records for the Marquesas Islands; the coastal fish fauna of the Marquesas Islands is increased from 415 to 495 species and the number of endemic species is increased from 48 to 68 species. This increases the percentage of species-level endemism for the Marquesas Islands to 13.7%, ranking as the third highest region of endemism for coral reef fishes in the Indo-Pacific. Only two other peripheral regions, the Hawai'ian Islands and Easter Island, have higher values.
ISSN: 1809-127X

Droits : http://creativecommons.org/licenses/by-nc-nd/
hal-01223491
https://hal-univ-perp.archives-ouvertes.fr/hal-01223491
https://hal-univ-perp.archives-ouvertes.fr/hal-01223491/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01223491/file/12228-51386-1-PB.pdf
DOI : 10.15560/11.5.1758

Éditeur(s) : HAL CCSD PeerJ
Résumé : International audience
The adaptative bleaching hypothesis (ABH) states that, depending on the symbiotic flexibility of coral hosts (i.e., the ability of corals to ''switch'' or ''shuffle'' their algal symbionts), coral bleaching can lead to a change in the composition of their associated Symbiodinium community and, thus, contribute to the coral's overall survival. In order to determine the flexibility of corals, molecular tools are required to provide accurate species delineations and to detect low levels of coral-associated Symbiodinium. Here, we used highly sensitive quantitative (real-time) PCR (qPCR) technology to analyse five common coral species from Moorea (French Polynesia), previously screened using only traditional molecular methods, to assess the presence of low-abundance (background) Symbiodinium spp. Similar to other studies, each coral species exhibited a strong specificity to a particular clade, irrespective of the environment. In addition, however, each of the five species harboured at least one additional Symbiodinium clade, among clades A–D, at background levels. Unexpectedly, and for the first time in French Polynesia, clade B was detected as a coral symbiont. These results increase the number of known coral-Symbiodinium associations from corals found in French Polynesia, and likely indicate an underestimation of the ability of the corals in this region to associate with and/or ''shuffle'' different Symbiodinium clades. Altogether our data suggest that corals from French Polynesia may favor a trade-off between optimizing symbioses with a specific Symbiodinium clade(s), maintaining associations with particular background clades that may play a role in the ability of corals to respond to environmental change. How to cite this article Rouzé et al. (2017), An updated assessment of Symbiodinium spp. that associate with common scleractinian corals from Moorea (French Polynesia) reveals high diversity among background symbionts and a novel finding of clade B.
ISSN: 2167-8359

Droits : info:eu-repo/semantics/OpenAccess
hal-01430294
https://hal-sde.archives-ouvertes.fr/hal-01430294
https://hal-sde.archives-ouvertes.fr/hal-01430294/document
https://hal-sde.archives-ouvertes.fr/hal-01430294/file/Rouze-2017-PeerJ-Updated.pdf
DOI : 10.7717/peerj.2856

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100-220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45 degrees rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises similar to 70% of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.
ISSN: 0148-0227

hal-00617528
https://hal.archives-ouvertes.fr/hal-00617528
https://hal.archives-ouvertes.fr/hal-00617528/document
https://hal.archives-ouvertes.fr/hal-00617528/file/2010JB007931.pdf
DOI : 10.1029/2010JB007931

Éditeur(s) : HAL CCSD
Résumé : Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink probably located in the tropics, particularly in the Amazon. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models.
ISSN: 1476-4687

hal-01204223
https://hal.archives-ouvertes.fr/hal-01204223
DOI : 10.1038/nature14283
PRODINRA : 294797
PUBMED : 25788097

Éditeur(s) : HAL CCSD Wiley/Blackwell
Résumé : International audience
Marine fishes exhibit spectacular phenotypic changes during their ontogeny, and the identification of their early stages is challenging due to the paucity of diagnostic morphological characters at the species level. Meanwhile, the importance of early life stages in dispersal and connectivity has recently experienced an increasing interest in conservation programmes for coral reef fishes. This study aims at assessing the effectiveness of DNA barcoding for the automated identification of coral reef fish larvae through large-scale ecosystemic sampling. Fish larvae were mainly collected using bongo nets and light traps around Moorea between September 2008 and August 2010 in 10 sites distributed in open waters. Fish larvae ranged from 2 to 100 mm of total length, with the most abundant individuals being <5 mm. Among the 505 individuals DNA barcoded, 373 larvae (i.e. 75%) were identified to the species level. A total of 106 species were detected, among which 11 corresponded to pelagic and bathypelagic species, while 95 corresponded to species observed at the adult stage on neighbouring reefs. This study highlights the benefits and pitfalls of using standardized molecular systems for species identification and illustrates the new possibilities enabled by DNA barcoding for future work on coral reef fish larval ecology.
ISSN: 1755-098X

hal-01342973
https://hal-univ-perp.archives-ouvertes.fr/hal-01342973
DOI : 10.1111/1755-0998.12293

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Serpentinization of olivine-rich troctolite from core 227, Integrated Ocean Drilling Program (IODP) Hole U1309D ranges from 10 to 90. Two episodes of serpentinization are recognized. The first, dominant in weakly serpentinized samples, is an approximately isochemical (except for water) replacement of olivine (Fo(8485)) by a mixture of serpentine (antigorite, Mg-number 92) and brucite (amakinite-rich; Mg-number 65). The compositions of the minerals in type 1 veins are a reflection of FeMg exchange between olivine and the brucite serpentine formed during early serpentinization. The early serpentinite veins (type 1) are thin ( 005 mm), irregular, and exploit pre-existing cracks in olivine. The presence of antigorite suggests that early serpentinization occurred at T 300C. Type 1 veins reflect rock-dominated serpentinization, became isolated early in their history, and persist as relicts in all but the most altered samples. The main episode of serpentinization is manifested by through-going lizardite (average Mg-number 96)magnetite veins (type 2). Type 2 veins define an anastomosing foliation, may be several millimeters in width and appear to exploit pre-existing, favorably oriented type 1 veins. Type 2 veins reflect open-system serpentinization. Magnetite in these veins formed by oxidation of the Fe in brucite and serpentine, whereas addition of silica to the system converted the Mg-component of the brucite to serpentine. Magnetite forms one or more distinct bands in the interior of the vein and is never in direct contact with relict olivine. A bruciteserpentine mixture, similar to that found in type 1 veins, but with lizardite instead of antigorite, is commonly present at the margins of type 2 veins (i.e. where they are in reaction contact with relict olivine). We interpret type 2 veins as a steady-state system where brucite continually forms at the olivinevein contact and then reacts out in the interior of the vein. This continual formation and destruction of brucite imposes an exceptionally low a(SiO2) on the system. Magnetite and olivine are never in contact in type 2 veins (or anywhere else) because the olivine-out reaction yields ferroan brucite and not magnetite. The desilication of serpentine in the type 2 veins is a reflection of the inherent instability of Fe-rich serpentine with respect to magnetite at low silica activity. Thus, the composition of serpentine in equilibrium with magnetite in serpentinites is a function of serpentinemagnetite and not serpentineolivine equilbria.
ISSN: 0022-3530

hal-00420931
https://hal.archives-ouvertes.fr/hal-00420931
DOI : 10.1093/petrology/egp004