Une gamme d'îles de référence, un atout majeur pour l'évaluation de programmes de restauration dans l'archipel de Kerguelen

The Kerguelen Archipelago is constituted by a main island (6 500 km2) and about sixty secondary islands (1-200 km2). Somee of these islands are pristine, while some others have been colonized by introduced plants, invertebrate species and, in some cases, by one or several alien mammals. Programs of ecological restoration began in 1992 on three islands, Verte I., Guillou I. and Cochons I. (respectively 150, 145 and 165 ha) damaged by the presence of mammals (rabbits, rabbits-cats-mice, rabbits-mice). The management action was the eradication of rabbits by poisoning. Due to the existence of reference islands (with or without introduced mammals), and of control islands (presence of rabbits), the Kerguelen Archipelago offers an unusual opportunity to distinguish the effects of the management intervention from those of other factors. For example, synchronised vegetation monitoring of habitats on a control island (Cimetière I., colonized by rabbits) has shown the role of this mammal in controlling one introduced Asteraceae (Taraxacum officinale). After rabbit eradication, this plant drastically increased in cover on the three experimental islands. Moreover, results from Mayes I. (without herbivores) and from the 4 other islands studied, emphasized the impact of the present climatic changes on the evolution of plant communities. This factor explains most of the decrease in cover of several native species, especially Acaena magellanica, with the timing of Dandelion's success linked to open land appearance. These observations confirmed the value of contemporary reference sites to analyze the advantages of restoration programs and to conduct future actionsL'archipel de Kerguelen est constitué d'une île principale (6 500 km2) et d'une soixantaine d'îles secondaires (1-200 km2). Certaines sont totalement indemnes d'espèces introduites, d'autres ont été colonisées par des espèces végétales et des invertébrés allochtones, et d'autres encore sont occupées, de plus, par un ou plusieurs mammifères introduits. Un programme de restauration écologique concernant trois îles (145 à 165 ha) dégradées par la présence de mammifères (lapin, lapin-souris, lapin-chat-souris) a été initié en 1992 par éradication du lapin. Par la présence d'îles de référence (sans herbivore introduit) et d'îles témoin (avec lapin), l'archipel de Kerguelen offre une situation exceptionnelle permettant de distinguer les effets de l'intervention de ceux d'autres facteurs. Le suivi synchronique de la végétation de différentes îles a permis de mettre en évidence, par exemple, le rôle du lapin sur le contrôle d'une Astéracée introduite (Taraxacum officinale) et l'importance des changements climatiques sur les trajectoires d'évolution des communautés végétales. Ces observations ont confirmé l'intérêt de disposer de références contemporaines pour analyser les bénéfices d'opérations de restauration et pour orienter les actions à veni

Spotlight on the invasion of a carabid beetle on an oceanic island over a 105-year period island

The flightless beetle Merizodus soledadinus, native to the Falkland Islands and southern South America, was introduced to the sub-Antarctic Kerguelen Islands in the early Twentieth Century. Using available literature data, in addition to collecting more than 2000 new survey (presence/absence) records of M. soledadinus over the 1991–2018 period, we confirmed the best estimate of the introduction date of M. soledadinus to the archipelago, and tracked subsequent changes in its abundance and geographical distribution. The range expansion of this flightless insect was initially slow, but has accelerated over the past 2 decades, in parallel with increased local abundance. Human activities may have facilitated further local colonization by M. soledadinus, which is now widespread in the eastern part of the archipelago. This predatory insect is a major threat to the native invertebrate fauna, in particular to the endemic wingless flies Anatalanta aptera and Calycopteryx moseleyi which can be locally eliminated by the beetle. Our distribution data also suggest an accelerating role of climate change in the range expansion of M. soledadinus, with populations now thriving in low altitude habitats. Considering that no control measures, let alone eradication, are practicable, it is essential to limit any further local range expansion of this aggressively invasive insect through human assistance. This study confirms the crucial importance of long term biosurveillance for the detection and monitoring of non-native species and the timely implementation of control measures

Résilience des communautés insulaires subantarctiques : facteurs influençant la vitesse de restauration écologique après éradication de mammifères introduits

Cattle were introduced to Amsterdam Island in 1871 and rabbits to the Kerguelen Archipelago in 1874. These herbivorous mammals caused severe damage to these terrestrial ecosystems. Two ecological restoration programs were implemented: cattle eradication from the southern part of Amsterdam Island (55 km2) in 1988 and rabbit eradication from three small islands (145 to 165 ha) at Kerguelen from 1992. On Amsterdam Island, in a temperate climate, the recovery of vegetation depended on the degree of damage caused to the environment by cattle. On the Jess eroded organic soils, recovery of native vegetation (e. g. Poa novarae, Blechnum penna-marina) was observed 10 years after cattle eradication. Conversely, on the thin and eroded mineral soils, an irreversible level of disturbance occurred: vegetation recovery was very slow and introduced plant species (e.g. Holcus lanatus) remained dominant while the cover of autochtonous species (Scirpus nodosus, Blechnum penna-marina) increased very slowly. Due to the cooler climate, ecological restoration processes were slower at Kerguelen than at Amsterdam Island. For some autochtonous species, such as Pringlea antiscorbutica and Azorella selago , presence of refuge areas on cliffs inaccessible to rabbits was important for colonization after rabbi! eradication. Vegetation changes depended greatly on the climatic changes recently recorded (characterised by a slight increase in temperature and more frequent summer drought). In contrast to the autochtonous species, most of the alien plants ( Taraxacum officinale, Senecio vulgaris...), originating from temperate regions, were favoured by these climatic changesL'introduction de bovins en 1871 sur l'île Amsterdam et de lapins en 1874 dans l'archipel de Kerguelen a eu un impact considérable sur les écosystèmes terrestres. Deux programmes de restauration écologique ont été mis en place, l'un en 1988 par élimination des bovins de la partie sud de l'île Amsterdam (55 km2), le second à partir de 1992 par éradication des lapins sur trois îles (1,45 à 1,65 km2) à Kerguelen. Sur l'île Amsterdam, les capacités et la vitesse de restauration des communautés dépendent du niveau de la perturbation des milieux engendrée par les bovins. Alors qu'une dizaine d'années a suffi à la restauration des communautés végétales sur certains secteurs dont les sols étaient peu dégradés, l'évolution est lente et les espèces introduites restent dominantes sur de larges secteurs où l'érosion du sol atteint un seuil d'irréversibilité. A Kerguelen, les processus de restauration, plus lents, ont été de plus fortement influencés et limités par les changements climatiques récents (sécheresse estivale de plus en plus fréquente) qui bénéficient aux espèces introduites, originaires de régions plus tempérées, et pénalisent les espèces locales pour lesquelles ces conditions sont entièrement nouvelle

Impact des changements climatiques et de la fréquentation humaine sur la biodiversité des îles subantarctiques françaises

L’invasion des écosystèmes par des espèces exotiques constitue, en conjonction avec les changements climatiques, une des plus grandes menaces pour la biodiversité mondiale, après la destruction des habitats. Même dans les régions antarctiques et subantarctiques, des espèces étrangères à la faune et à la flore locales ont été introduites dès la fin du 18e siècle. La majorité de ces introductions sont associées à la fréquentation humaine et aux visites des navires. Par ailleurs, comme le prédisent la plupart des modèles, les régions de hautes latitudes sont les plus sensibles aux changements climatiques. Les observations faites à Kerguelen confirment cette tendance et attestent de l’impact déjà bien visible des augmentations de température (1,3°C depuis le milieu des années 1960) et des déficits hydriques estivaux récurrents ces dernières années. Avec ces changements climatiques rapides, une augmentation du nombre d’introductions d’espèces et de leur succès d’établissement est attendue, de même que la fragilisation de la faune et la flore locales, d’où de notables conséquences prévisibles quant à la biodiversité de ces régions très particulières.Biological invasions, in connection with climate changes, are amongst the most significant threats to biodiversity worldwide. Even in antarctic and subantarctic regions, alien species arrived since the end of the 18th century. Most of these introductions are obviously associated with human activities and ship landings. Otherwise, as predicted by many global circulation models, rates of warming are expected to be stronger at higher latitudes. Our study on the Kerguelen Islands confirms this trend and demonstrates that the effects of warming (+ 1.3°C since the mid 1960s) and summer droughts on plants and invertebrates are now visible. With climate change occurring rapidly, both the numbers of introductions and the success of colonisation by alien species are likely to increase, with as consequence subsequent impacts on the entire ecosystem

Common variants in Alzheimer’s disease and risk stratification by polygenic risk scores

Funder: Funder: Fundación bancaria ‘La Caixa’ Number: LCF/PR/PR16/51110003 Funder: Grifols SA Number: LCF/PR/PR16/51110003 Funder: European Union/EFPIA Innovative Medicines Initiative Joint Number: 115975 Funder: JPco-fuND FP-829-029 Number: 733051061Genetic discoveries of Alzheimer's disease are the drivers of our understanding, and together with polygenetic risk stratification can contribute towards planning of feasible and efficient preventive and curative clinical trials. We first perform a large genetic association study by merging all available case-control datasets and by-proxy study results (discovery n = 409,435 and validation size n = 58,190). Here, we add six variants associated with Alzheimer's disease risk (near APP, CHRNE, PRKD3/NDUFAF7, PLCG2 and two exonic variants in the SHARPIN gene). Assessment of the polygenic risk score and stratifying by APOE reveal a 4 to 5.5 years difference in median age at onset of Alzheimer's disease patients in APOE ɛ4 carriers. Because of this study, the underlying mechanisms of APP can be studied to refine the amyloid cascade and the polygenic risk score provides a tool to select individuals at high risk of Alzheimer's disease

Mendelian randomization implies no direct causal association between leukocyte telomere length and amyotrophic lateral sclerosis

Funder: QingLan Research Project of Jiangsu for Outstanding Young TeachersFunder: Project funded by Postdoctoral Science Foundation of Xuzhou Medical UniversityFunder: Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) for Xuzhou Medical UniversityAbstract: We employed Mendelian randomization (MR) to evaluate the causal relationship between leukocyte telomere length (LTL) and amyotrophic lateral sclerosis (ALS) with summary statistics from genome-wide association studies (n = ~ 38,000 for LTL and ~ 81,000 for ALS in the European population; n = ~ 23,000 for LTL and ~ 4,100 for ALS in the Asian population). We further evaluated mediation roles of lipids in the pathway from LTL to ALS. The odds ratio per standard deviation decrease of LTL on ALS was 1.10 (95% CI 0.93–1.31, p = 0.274) in the European population and 0.75 (95% CI 0.53–1.07, p = 0.116) in the Asian population. This null association was also detected between LTL and frontotemporal dementia in the European population. However, we found that an indirect effect of LTL on ALS might be mediated by low density lipoprotein (LDL) or total cholesterol (TC) in the European population. These results were robust against extensive sensitivity analyses. Overall, our MR study did not support the direct causal association between LTL and the ALS risk in neither population, but provided suggestive evidence for the mediation role of LDL or TC on the influence of LTL and ALS in the European population

Genetic variation across RNA metabolism and cell death gene networks is implicated in the semantic variant of primary progressive aphasia

The semantic variant of primary progressive aphasia (svPPA) is a clinical syndrome characterized by neurodegeneration and progressive loss of semantic knowledge. Unlike many other forms of frontotemporal lobar degeneration (FTLD), svPPA has a highly consistent underlying pathology composed of TDP-43 (a regulator of RNA and DNA transcription metabolism). Previous genetic studies of svPPA are limited by small sample sizes and a paucity of common risk variants. Despite this, svPPA\xe2\x80\x99s relatively homogenous clinicopathologic phenotype makes it an ideal investigative model to examine genetic processes that may drive neurodegenerative disease. In this study, we used GWAS metadata, tissue samples from pathologically confirmed frontotemporal lobar degeneration, and in silico techniques to identify and characterize protein interaction networks associated with svPPA risk. We identified 64 svPPA risk genes that interact at the protein level. The protein pathways represented in this svPPA gene network are critical regulators of RNA metabolism and cell death, such as SMAD proteins and NOTCH1. Many of the genes in this network are involved in TDP-43 metabolism. Contrary to the conventional notion that svPPA is a clinical syndrome with few genetic risk factors, our analyses show that svPPA risk is complex and polygenic in nature. Risk for svPPA is likely driven by multiple common variants in genes interacting with TDP-43, along with cell death,x` working in combination to promote neurodegeneration

Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity

The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once

Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity

The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once