Search publications of the members of the Royal Belgian institute of natural Sciences
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Possible effects of global environmental changes on Antarctic benthos : a synthesis across five major taxa
- Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed.
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Guide taxonomique des oligochètes dulçaquicoles du Maghreb
- Résumé Ce guide fournit l’information taxonomique pour les 68 espèces d’oligochètes dulçaquicoles connus à l’heure actuelle au Maghreb, au sens strict, c’est-à-dire la région d’Afrique du nord qui regroupe le Maroc, l’Algérie et la Tunisie. Au niveau du Grand Maghreb, ce guide est potentiellement valable pour la Libye mais pas pour la Mauritanie. Une introduction est faite au milieu dulçaquicole du Maghreb et sa spécificité pour les oligochètes, ainsi qu’une présentation de la biologie et la diversité globale des oligochètes. Les récentes avancées dans le domaine de la nomenclature et de la classification du groupe sont intégrées. Un panorama détaillé des familles maghrébines d’oligochètes est dressé, précédé par des introductions à l’anatomie générale et aux caractères taxonomiques des oligochètes. Les aspects pratiques liés à l’échantillonnage et les techniques de préparation des spécimens et leur conservation sont détaillés, ainsi que les étapes à suivre pour les identifier. Une clé d’identification au niveau spécifique est fournie pour chaque famille, valable uniquement pour les oligochètes connus à l’heure actuelle au Maghreb, mais en précisant les espèces susceptibles d’y être rencontrées en raison de leur distribution biogéographique présente. Enfin, ce guide donne la description d’Aktedrilus yacoubii (Naididae, Phallodrilinae), espèce nouvelle pour la science et le Maghreb. Mots-clés – Clitellata, oligochètes dulçaquicoles, Maghreb, clés d’identification, taxonomie, liste d’espèces, échantillonnage, préparation de spécimens. Abstract This guide provides taxonomical information for the 68 freshwater oligochaete species known to date in Maghreb sensu stricto, namely this region of Northern Africa that includes Morocco, Algeria and Tunisia. At the “Grand Maghreb” level, the guide is potentially valid for Libya as well but not for Mauritania. An introduction to the freshwater environment of Maghreb and its peculiarity vis-à-vis the oligochaetes is given, as well as a presentation of the biology and general diversity of oligochaetes. Recent nomenclatural and classification advances are integrated. A comprehensive overview of Maghrebin oligochaete families is given, preceded by introductions into the general anatomy and taxonomic traits of oligochaetes. Practical aspects of sampling, and techniques of specimen preparation and conservation are detailed, as well as steps required for their identification. An identification key, at the species level, is provided for each family, only valid for oligochaetes presently known from Maghreb; however, species likely to be found in the future, because of their current biogeographic distribution, are also mentioned. Lastly, this guide gives the description of Aktedrilus yacoubii (Naididae, Phallodrilinae), a species new for science and Maghreb. Keywords – Clitellata, freshwater oligochaetes, Maghreb, identification keys, taxonomy, species list, sampling, specimen processing.
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BIANZO II: Biodiversity of three representative groups of the Antarctic Zoobenthos - Coping with Change. Final Report
- 1) SUMMARY a) Context The improvement of our understanding of ecological processes and the role of biodiversity in the Southern Ocean ecosystems remains a high priority on the research agenda in today’s changing world and is inextricably linked to sustainable development policies on a global scale. Global environmental changes influence species distributions and consequently the structure of communities and ecosystems. Only advances in our knowledge of the Southern Ocean biodiversity and processes important for ecosystem functioning can allow us to address complex evolutionary and ecological questions and enable estimations of the expected change of the biota distribution and composition. Polar regions experience greater rates of global change than any other region in the world. Their biota are highly adapted to the extreme environment they are living in and appear vulnerable to shifts in environmental conditions. Antarctic marine species are especially more sensitive to temperature variation as their physiology is set to a narrow range of temperatures. Also changes in food quality and quantity, together with other environmental shifts such as in pH of the seawater, are likely to impact densities, biomass and community composition but also functional aspects of the Antarctic biota. Because of the key-role of the Southern Ocean for the global ocean system and the growing impact of global environmental change, it is crucial to establish comprehensive baseline information on Antarctic marine biodiversity as a sound benchmark against which future change can be assessed reliably. It is equally important to understand better the ability of taxa to cope with changes in environmental parameters (temperature, pH, ice cover, food quantity and quality) linked to global change, and this from the individual to the community level. Imperative in this approach is to assess how structural and functional characteristics of the biota may be affected by a changing climate. Finally, advanced integrative spatial modelling of the distribution of key species in relation to environmental conditions is needed to predict the future of the marine ecosystems related to climate change. These aspects are addressed in the Bianzo II project by focusing on benthic organisms and communities, specifically representatives from three different size classes of the zoobenthos: Nematoda (meiobenthos), Amphipoda (macrobenthos) and Echinoidea (megabenthos). These three groups are characterised by a high diversity and many of the well over 4000 Antarctic benthic species described so far (Clarke & Johnston, 2003) belong to these taxa. These three selected benthic taxa are also ecologically important in terms of biomass, their role in biogeochemical cycles (C and N) and the trophic role they fulfil in the benthic ecosystem. Furthermore, they are characterised by different biogeographical and diversity patterns, speciation mechanisms, and reproductive and dispersal strategies. Because of these differences and the intrinsic ecological variability between these taxa, it is difficult to assess the extent to which global change will affect the Antarctic benthos in general. Rarely do biodiversity and ecological studies focus on multiple benthic groups. Yet, combining putative size groups in ecological/biodiversity research is imperative to understand the benthic ecosystem as a complex and interactive unity. b) Objectives Climate change and its complex and interactive chain of associated effects will affect the physiology, distribution, phenology, and ontogeny of many Antarctic benthic organisms, but the resulting changes from the species to the community level remain poorly quantified and understood. Individual species may appear vulnerable to environmental shifts or regime changes, but community and ecosystem responses may not act accordingly. Therefore we investigated the biodiversity and responses of the three representative groups of benthic organisms to climate change effects from individual species, over populations, up to the community level During its first phase (2007-2008), BIANZO II aimed at investigating (1) biodiversity patterns of the Antarctic zoobenthos and their causal processes by focussing on the three selected benthic groups (Work package 1: NOWBIO); Furthermore (2) trophodynamic aspects of each of the benthic groups, and their ability to cope with temperature and temperature-related changes (i.e. food composition and availability) but also the effect of pH of the seawater were on the benthos (Work package 2: DYNABIO). In the second phase (2009-2010) of the project, a joint review paper dealing with the effects of global climate change on the Antarctic zoobenthos is being written, based on the results of experiments, field results and literature data. Information collected in previous studies and in the first two work packages of this project was also used to develop a habitat suitability model in order to identify the drivers of benthic distribution patterns and forecast possible changes of benthic communities related to global change (Work package 3: FOREBIO). c) Conclusions i) NOWBIO (1) Benthic biodiversity in new ice free habitats Due to large-scale ice-shelf disintegration events, the Antarctic Larsen A and B areas along the Eastern Antarctic Peninsula recently became ice-free. Our study is the first one to investigate benthic communities and their response to the collapse of ice shelves in this area. At the time of sampling, meiofauna community structure at the inner stations, most remote from the original ice margin, was not or only slightly influenced by colonization, and might be structured by local environmental conditions. Communities living close to the former ice-shelf edge are believed to be at an intermediate or late stage of succession. Densities and diversity here were comparable to those at other more northern Antarctic stations in the Weddell Sea, whereas they were considerably lower at the inner stations. The three echinoid species collected in Larsen A&B areas are good candidates as pioneering species in a changing marine environment. They are known as indirect developers (or at least non-brooders), consistent with high dispersal capabilities. Moreover, this is congruent with the wide Antarctic distribution of these species. These examples stand in contrast to other Antarctic echinoids which are known as direct developers that brood their young and, accordingly, are supposed to present low dispersal capacities. The three Larsen species also display a ‘generalist’ feeding behaviour which can also be considered a characteristic of pioneering species. Furthermore, the symbiotic communities of echinoids in the Larsen area showed a low diversity and a strong similarity with epibionts present on stones, something which has not been observed in other regions so far. These results suggest that ectosymbioses linked to cidaroids could contribute to benthic colonization of the seafloor in these new ice free areas. The Larsen ice-shelf disintegration also led to the discovery of a low-activity methane seep. The observation of elevated densities, subsurface maxima and high dominance of one nematode species was similar to other cold-seep ecosystems world-wide and suggested a dependence on a chemosynthetic food source. However, stable 13C isotopic signals were indicative of phytoplankton-based feeding. This implied that the community was in transition from a chemosynthetic community to a classic phytodetritus feeding community, a temporary ecotone as it were. The characteristic parthenogenetic reproduction of the dominant species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.
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Origin and patterns of biodiversity of subterranean aquatic Clitellata
- Subterranean ecosystem biodiversity is characterized by a unique combination of four features that may account for its patterns and fluctuations at a global scale: (1) a low number of lineages due to environmental harshness, (2) a high proportion of endemic species as a result of habitat fragmentation and isolation, (3) a high level of relict taxa, best explained by the relative stability and antiquity of the habitat compared with most superficial habitats, and (4) food webs that are truncated at both the bottom (no primary producers) and the top (few or no predators and no specialized ones). In this review, we present a synthesis of the current state of knowledge of groundwater oligochaetes, and we investigate in what extent their biodiversity meets these criteria. The present knowledge is strongly biased in favour of the West-Palaearctic region, in particular the karst of Southern Europe. While our understanding of groundwater biodiversity in Europe and the United States has gained much during these last decades, many areas are undersampled in the world. To date, more than 300 nominal species have been found in ground waters all over the world (on about 1,700 and 1,100 aquatic and freshwater oligochaete species, respectively). Most of these species should be considered as incidentals or waifs; however, about one-third of them are found exclusively in this environment (stygobionts). Among the 21 families that are fully aquatic or include species occurring in aquatic habitats, 16 families are present in ground water. Stygobiont species belong to only 7 different families, harbouring 42 genera among which 17 are represented by a single species. Thirty-four per cent of the species are representatives of only two genera: Trichodrilus (Lumbriculidae) and Rhyacodrilus (Naididae). With 9 species, all being stygobiont, the Parvidrilidae is unique in being the only family, worldwide, comprising taxa that are restricted to groundwater habitats. Data on the distribution of stygobiont oligochaetes suggest pronounced endemism, nearly 60% of the species being known only from their type locality. The origins of subterranean oligochaete biodiversity probably involve multiple and successive colonization processes, both from marine and freshwater environments. The current distribution of Parvidrilidae, Rhyacodriloides (Rhyacodriloidinae), Delaya (Haplotaxidae), or species belonging to primarily marine genera, may be explained when assuming that these species are palaeoendemics or relicts, namely survivors of an old fauna that has long since become extinct in the surrounding areas. Aquatic oligochaetes appear to be pre-adapted to live in the subterranean environment. In the absence of genuine troglomorphic characters, their stygobiotic status can only be inferred from their exclusive presence in the subterranean environment. Valuable studies to enhance knowledge of subterranean aquatic oligochaetes will probably take more advantage of investigating adaptations that enable them to face scarceness of food and oxygen in groundwater, rather than focussing on an uncertain quest for morphological adaptations. Promising approaches would be to compare related hypogean and epigean species within the same genus, such as in Trichodrilus and Rhyacodrilus, or ecosystems the most similar to the underground such as lake hypolimnia and the deep sea. Keywords: ground water, Clitellata, biodiversity, patterns, endemism, relictuality, adaptation.
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Molecular and morphological evidence for the existence of several species with restricted range within the cosmopolite eurybathic deep-sea Lysianassoid amphipod Eurythenes gryllus sensu lato
- Introduction Eurythenes gryllus (Lichtenstein, 1822) is a presumed cosmopolitan eurybathic bentho-pelagic giant deep-sea amphipod. However, previous studies already highlighted genetically divergent lineages in the Atlantic and Pacific Oceans, which appeared to be vertically stratified, and minor morphological differences between populations were also recorded. Material and methods With an aim to quantify the geographic and bathymetric patterns of genetic variations, the genetic diversity in Eurythenes gryllus was investigated at the global scale (Arctic, Atlantic, Pacific and Southern Oceans) using three different genes (COI, 16S rRNA, 28S rRNA). This genetic analysis was followed by a thorough morphological study. Results Phylogenetic and phylogeographic analyses revealed the existence of at least seven well-supported clades, two bathyal and five abyssal, which were separated by genetic distances at the level of usual interspecific divergences. Furthermore, a clear genetic break was observed between specimens sampled above and below 3000 m. One clade comprised specimens from several bathyal sites in the Arctic and Southern Oceans. A subsequent morphological analysis confirmed the genetic findings and revealed small but consistent differences between the different clades, which will be described as separate species. Discussion This bathymetric break below 3000 m has already been reported for several organisms and regions, suggesting its role as a ubiquitous phylogeographic barrier for barophysical tolerance. The widely distributed Eurythenes clade, which is presumably the true E. gryllus, is, to our knowledge, the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. The present results clearly highlight the difficult nature of research on the systematics of deep-sea crustaceans and shows that the abyss is a more complex environment than previously assumed, which is likely to harbour an important hidden diversity.
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First report of the exotic blue planarian, Caenoplana coerulea (Platyhelminthes, Geoplanidae), on Menorca (Balearic Islands, Spain)
- In April 2009 two specimens of a terrestrial flatworm were collected from under a rock in an orchard at Ciutadella de Menorca on the easternmost Balearic island of Menorca (Spain). Their external morphology suggested that both specimens belonged to the invasive blue planarian Caenoplana coerulea, a species which is native to eastern Australia. Sequence data of a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) and of the entire 18S ribosomal RNA confirm its identification. This is one of the first records of the species in Europe where it has only been found in one locality in the United Kingdom, France and NE Spain.
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Taxonomic revision of Isocetus depauwi (Mammalia, Cetacea, Mysticeti) and the phylogenetic relationships of archaic ‘cetothere’ mysticetes
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A new genus and species of Late Miocene inioid (Cetacea: Odontoceti) from the Meherrin River, North Carolina, U.S.A.
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Osteological associations with unique tooth developement in manatees (Trichechidae, Sirenia): a detailed look at modern Trichechus and a review of the fossil record
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Histology and growth pattern of the pachy-osteosclerotic premaxillae of the fossil beaked whale Aporotus recurvirostris (Mammalia, Cetacea, Odontoceti)
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Palaeolithic dog skulls at the Gravettian Předmostí site, the Czech Republic
- Whether or not the wolf was domesticated during the early Upper Palaeolithic remains a controversial issue. We carried out detailed analyses of the skull material from the Gravettian Předmostí site, Czech Republic, to investigate the issue. Three complete skulls from Předmostí were identified as Palaeolithic dogs, characterized by short skull lengths, short snouts, and wide palates and braincases relative to wolves. One complete skull could be assigned to the group of Pleistocene wolves. Three other skulls could not be assigned to a reference group; these might be remains from hybrids or captive wolves. Modifications by humans of the skull and canine remains from the large canids of Předmostí indicate a specific relationship between humans and large canids.
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Rostral densification in beaked whales: diverse processes for a similar pattern
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Intra-specific morphological variability in the cave bear Ursus spelaeus (Mammalia, Carnivora, Ursidae) from the Trou du Sureau (Montaigle caves, Belgium) using an outline analysis
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Tusk-bearing beaked whales from the Miocene of Peru: sexual dimorphism in fossil ziphiids?
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Van wolf tot woef
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Serial population extinctions in a small mammal indicate Late Pleistocene ecosystem instability
- The Late Pleistocene global extinction of many terrestrial mammal species has been a subject of intensive scientific study for over a century, yet the relative contributions of environmental changes and the global expansion of humans remain unresolved. A defining component of these extinctions is a bias toward large species, with the majority of small-mammal taxa apparently surviving into the present. Here, we investigate the population-level history of a key tundra-specialist small mammal, the collared lemming (Dicrostonyx torquatus), to explore whether events during the Late Pleistocene had a discernible effect beyond the large mammal fauna. Using ancient DNA techniques to sample across three sites in North-West Europe, we observe a dramatic reduction in genetic diversity in this species over the last 50,000 y. We further identify a series of extinction-recolonization events, indicating a previously unrecognized instability in Late Pleistocene small-mammal populations, which we link with climatic fluctuations. Our results reveal climate-associated, repeated regional extinctions in a keystone prey species across the Late Pleistocene, a pattern likely to have had an impact on the wider steppe-tundra community, and one that is concordant with environmental change as a major force in structuring Late Pleistocene biodiversity.
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A Miocene Ziphiid (Cetacea: Odontoceti) from Calvert Cliffs, Maryland, U.S.A.
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The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru
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Palaeolithic dogs and the early domestication of the wolf: a reply to the comments of Crockford and Kuzmin
- This is a response to the comments of Crockford and Kuzmin (2012) on our identification of Palaeolithic dogs from different European Palaeolithic sites. In their comments Crockford and Kuzmin (2012) present some errors, misunderstandings and misrepresentations that we remedy here. In our opinion, the early wolf domestication must be regarded as an intimate relationship between humans and canids including the breeding of the latter by prehistoric people, resulting in the European Palaeolithic dogs.
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Inferences on dog domestication - genetic analysis of the most ancient dogs utilizing DNA capture arrays
