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19 pages; International audience; Species distribution models (SDMs) are increasingly used in ecological and biogeographic studies by Antarctic biologists, including for conservation and management purposes. During the modelling process, model calibration is a critical step to ensure model reliability and robustness, especially in the case of SDMs, for which the number of selected environmental descriptors and their collinearity is a recurring issue. Boosted regression trees (BRT) was previously considered as one of the best modelling approach to correct for this type of bias. In the present study, we test the performance of BRT in modelling the distribution of Southern Ocean species using different numbers of environmental descriptors, either collinear or not. Models are generated for six sea star species with contrasting ecological niches and wide distribution ranges over the entire Southern Ocean. For the six studied species, overall modelling performance is not affected by the number of environmental descriptors used to generate models, BRT using the most informative descriptors and minimizing model overfitting. However, removing collinear descriptors also helps reduce model overfitting. Our results confirm that BRTs may perform well and are relevant to deal with complex and redundant environmental information for Antarctic biodiversity distribution studies. Selecting a limited number of non-collinear descriptors before modelling may generate simpler models and facilitate their interpretation. The modelled distributions do not differ noticeably between the different species despite contrasting species ecological niches. This unexpected result stresses important limitations in using SDMs for broad scale spatial studies, based on limited, spatially aggregated data, and low-resolution descriptors.

Comme dans toutes les mers chaudes et tempérées, les écosystèmes marins côtiers des régions subantarctiques concentrent une importante biodiversité. Ils sont confrontés à des changements environnementaux dont les effets restent encore mal cernés (évolution des températures, modification des courants marins, glissements saisonniers, migration d’espèces…). Les écosystèmes marins côtiers des îles subantarctiques françaises ont été relativement peu étudiés et la biodiversité benthique y est encore mal connue comparée à celle des domaines pélagique et terrestre. Fort de ce constat, le programme PROTEKER (http://www.proteker.net/?lang=en) de l’Institut polaire français Paul- Emile Victor (n°1044 de l’IPEV), mené en collaboration avec la Réserve naturelle des Terres australes françaises, a vu le jour en 2011 avec pour objectif la mise en place d’un observatoire marin pour le suivi écologique de la biodiversité marine côtière des Iles Kerguelen et l'évaluation des effets des changements environnementaux sur cette biodiversité. Il envisage une approche pluridisciplinaire : mesures océanographiques, cartographie benthique, analyses génétiques, éco-physiologiques, isotopiques et écologiques. Outre l'inventaire et le suivi des habitats et d'assemblages d'espèces benthiques, il a aussi pour ambition de fournir des données scientifiques précises aux gestionnaires en charge des politiques de conservation. Réalisée au cours de 3 campagnes d'été entre 2011 et 2014, la première phase du programme a permis de réunir les anciennes données de biodiversité disponibles, de compléter ces données par de nouveaux prélèvements (plongées dans les 20 premiers mètres, chalutages à 50 et 100 m) et de nouvelles observations (ROV), de sélectionner et d'instrumenter des stations de référence (mise en place de thermo-enregistreurs et de placettes de colonisation) pour la mise en oeuvre de la seconde phase du programme. La seconde phase du programme dans laquelle nous nous trouvons (2015-2018) a pour objectif le suivi des stations de référence (relève des instruments installés, observations et prélèvements associés aux placettes de colonisation), la cartographie des habitats benthiques associés ( R.O.V. et prélèvements en plongée et par chalutage) et le renforcement des observations et des analyses (caractérisations génétiques, trophiques et écologiques de taxons indicateurs). Les résultats attendus doivent permettre de produire des modèles de distribution de la biodiversité marine côtière aux Kerguelen et des modèles de sensibilité face aux changements environnementaux attendus. Cette seconde phase s’appuie sur quatre campagnes d’été pour la mise en oeuvre des cinq volets suivants : A/ Mesures de paramètres de milieu et suivi des sites (instrumentation) B/ Caractérisation des différents habitats et des communautés (cartographie benthique, échantillonnage et observations) C/ Inventaire de la biodiversité marine et analyse de la structuration génétique d’espèces cibles entre les différents secteurs des Kerguelen, et entre les Kerguelen et les autres îles subantarctiques (génétique des populations) D/ Etudes éco-physiologiques d’espèces cibles E/ Modélisation de la distribution d’espèces et de communautés &nbsp

A new marine fossil assemblage from the Early Triassic shows unexpected phyletic diversity and functional complexity., In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.

GENUS CALYMNE THOMSON, 1877 Diagnosis Test of adults very high, ovoid in aboral view, and compressed laterally with low ambitus; anterior end rounded without frontal groove; posterior end almost vertically truncated. Large spoon-shaped spines present on plastronal area; frills of large paddleshaped spines around periproct and aborally on the posterior end; subanal tuft of large pointed spines. Other significant features are important in identification of the genus but are present in other holasteroids and therefore not diagnostic for Calymne alone. These are as follows. Orthosternous plastron with small labrum in contact with sternal plate; interambulacra 1 and 4 meridoplacous, interambulacra 2 and 3 amphiplacous in adults; anterior and posterior pairs of genital plates separated by pair of ocular plates; two gonopores on genital plates 2 and 3. Uniporous ambulacra. Peristome flush with test; periproct supramarginal, located at top of posterior face. Marginal orthofasciole crossing plates 5.a.4 and 5.b.5. Rostrate pedicellariae of three types; ophicephalous pedicellariae umbrella-shaped; triphyllous pedicellariae present; tridentate and globiferous pedicellariae absent. Genotype and only known species: Calymne relicta., Published as part of Saucede, Thomas, Mironov, Alexander N., Mooi, Rich & David, Bruno, 2009, The morphology, ontogeny, and inferred behaviour of the deep-sea echinoid Calymne relicta (Holasteroida), pp. 630-648 in Zoological Journal of the Linnean Society 155 (3) on page 632, DOI: 10.1111/j.1096-3642.2008.00461.x, http://zenodo.org/record/5445061, {"references":["Thomson CW. 1877. The voyage of the ' Challenger'. The Atlantic. A primary account of the general results of the exploring voyage of H. M. S. ' Challenger' during the year 1873 and the early part of the year 1876. London: MacMillan and Co."]}

CALYMNE RELICTA THOMSON, 1877 Calymne relicta – Thomson, 1877: 397, figs 102–103; Agassiz, 1881: 155–157, pls XXXIV, XXXIX 24–26, XL 63–65, XLIII 24, XLIV 47, 48; Lovén, 1883: 90; Mortensen, 1907: 53–54, 86, text-fig. 7, pls X 5, 6, 30; Clark, 1917: 125; Clark, 1925: 188; Mortensen, 1950: 127–131; Mooi & David, 1996: figs 9p, 12k; Smith, 2004: 146–149, text-fig. 7. Diagnosis As for the genus., Published as part of Saucede, Thomas, Mironov, Alexander N., Mooi, Rich & David, Bruno, 2009, The morphology, ontogeny, and inferred behaviour of the deep-sea echinoid Calymne relicta (Holasteroida), pp. 630-648 in Zoological Journal of the Linnean Society 155 (3) on pages 632-633, DOI: 10.1111/j.1096-3642.2008.00461.x, http://zenodo.org/record/5445061, {"references":["Thomson CW. 1877. The voyage of the ' Challenger'. The Atlantic. A primary account of the general results of the exploring voyage of H. M. S. ' Challenger' during the year 1873 and the early part of the year 1876. London: MacMillan and Co.","Agassiz A. 1881. Report on the Echinoidea, dredged by H. M. S. Challenger during the years 1873 - 1876. In: Thomson CW, ed. Report of the scientific results of the voyage of H. M. S. Challenger during the years 1873 - 76. Zoology 3 (9). Report on the Echinoidea. London: Her Majesty's Stationery Office, 1 - 321.","Loven S. 1883. On Pourtalesia, a genus of Echinoidea. Kongliga Svenska Vetenskaps-Akademiens Handlingar 19: 1 - 95.","Mortensen T. 1907. Echinoidea II. The Danish ingolfexpedition. Copenhagen: Bianco Luno.","Clark HL. 1917. Hawaiian and other Pacific Echini. The Echinoneidae, Nucleolitidae, Urechinidae, Echinocorythidae, Calymnidae, Pourtalesiidae, Palaestomatidae, Aeropsidae, Palaeopneustidae, Hemiasteridae and. Spatangidae. Memoirs of the Museum of Comparative Zoology 46: 85 - 283.","Clark HL. 1925. A catalogue of the Recent sea-urchins (Echinoidea) in the collections of the British Museum (Natural History). London: Trustees of the British Museum.","Mortensen T. 1950. A monograph of the Echinoidea, Spatangoida 1. Copenhagen: Reitzel.","Mooi R, David B. 1996. Phylogenetic analysis of extreme morphologies: deep-sea holasteroid echinoids. Journal of Natural History 30: 913 - 953.","Smith AB. 2004. Phylogeny and systematics of holasteroid echinoids and their migration into the deep-sea. Palaeontology 47: 123 - 150."]}