1,721,012 research outputs found
Evidence for a single population expansion event across 24,000 km: the case of the deep‑sea scavenging amphipod Abyssorchomene distinctus
No full textAnthropogenic activities such as mining pose a putative threat to deep-sea ecosystems and baseline studies of key indicator species are required to assess future loss of biodiversity. We examined population genetic structure, connectivity, cryptic diversity and phylogeography of the deep-sea scavenging amphipod, Abyssorchomene distinctus, using DNA sequence data (mitochondrial COI and nuclear 28S genes) from 373 specimens collected from six abyssal basins. We observed a striking absence of cryptic diversity, suggesting a single, widely distributed species in the Pacific and Indian Ocean. A single event of population expansion across distances up to 24,000 km is further supported by a main ancestral haplotype in the star-like shaped COI haplotype network, a skewed nucleotide mismatch distribution and deviations from evolutionary neutrality tests. In the Pacific, A. distinctus showed weak genetic population structure and low differentiation between the basins of the Clarion-Clipperton Zone and the DISCOL Experimental Area, suggesting a possible higher chance of recovery from deep-sea mining impacts. However, since our data indicate a single recent historic population expansion event, A. distinctus populations will likely be affected to unknown extents, as the exact drivers shaping distribution and dispersion of A. distinctus are still unclear.We would like to acknowledge funding by the Belgian Science and Policy Ofce (BELSPO) for both JPI-Oceans “Mining Impact” Projects (BR/15/MA/JPI-DEEPSEA1 and BR/15/MA/JPI-DEEPSEA2).
We would like to thank the crew of the Research Vessel “Sonne” for their support during sampling. The authors thank Henri Robert for assistance during the feld campaign and Cedric d’Udekem d’Acoz for taxonomic identifcations. We furthermore are grateful to Ms. Dorien Aerts for the provided guidance to Deborah W. E. Dupont in morphological verifcation and dissection as well as practical support during molecular work
Describing novel mitochondrial genomes of Antarctic amphipods
Full text linkpeer reviewedBelgian Science Policy (Belspo) as part of the project ‘Refugia and Ecosystem Tolerance in the Southern Ocean
Selbstorganisierung bei Anemonenfischen und die Auswirkungen der marinen Zierfischerei in Spermonde Archipel, Indonesien: Bedeutung für die Bewirtschaftung und Erhaltung
No full textThe yearly amount of traded by middlemen on Spermonde Archipelago (Indonesia) is estimated to about 140,000 specimens A. ocellaris and more than 31,000 anemones. Both A. ocellaris and sea anemone densities (p < 0.01) were significantly lower at reefs with a high exploitation than at reefs with a low exploitation. The size of A. ocellaris individuals was significantly smaller in Barrang Lompo than in Samalona (p < 0.01). The private alleles and allelic richness in Samalona were 4% significantly higher than in Barrang Lompo. The allelic richness was positively correlated with the fish density (p < 0.05). Fish stays largely in place despite its pelagic larvae stage (44 % - 60.7 % self-recruitment). The genetic relatedness revealed a close relation between individuals within a group of A. ocellaris in Barrang Lompo. Conversely, unrelated individuals of A. ocellaris in Samalona and of A. perideraion in Barrang Lompo were observed. Altogether, these results provide important insights how marine ornamental fishery has impacted the population of anemonefish and its host in Spermonde Archipelago
Taxonomischen und in den funktionalen Charakteristika bedingen, die zwischen Rifffischgemeinschaften auf lokaler und regionaler Ebene beiderseits des Isthmus von Panama.
No full textThis thesis presents the results of a comparative study of reef fish communities on either side of the Western Isthmus of Panama (IOP). 288 visual censuses were carried out in each region. 128 fish species of 38 families were found in the Caribbean and 126 species of 44 families in the Pacific. The numbers of families and species do not differ markedly but the number of species recorded per sampling area was higher in the Pacific. Reef fishes depend on recruitment success, which is related to local oceanography and the connectivity and diversity of habitats, rather than to coral cover and diversity. Herbivores predominate in the Caribbean; planktivores and piscivores in the Pacific. Most reef fish reach larger sizes in Pacific. In both regions, the highest number of species is found in exposed rocky zones with high substrate diversity and complexity; followed by massive coral reefs. Individuals are smaller on low-complexity substrates in the Caribbean and in coral branches and holes in the Pacific, which provide refuge areas from predation and strong water movements. Better swimmers occur typically in exposed zones in Caribbean and have a wide spatial distribution in Pacific. Geminate species show strong habitat plasticity on both sides of the IOP, but retain similar habitat preferences in terms of morphology and depth regardless of the taxonomy of the benthic fauna and flora
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Moleculare Methoden zur Artidentifizierung und Populationsbestimmung Mariner Organismen
No full textSessile or site attached marine species rely on the dispersal of their pelagic larvae to ensure the exchange of reproductive individuals within and among subpopulations. The resultant and continued mixing of genetic identities constitutes their population connectivity and can ensure resilience against disturbance, disease or local extinctions. Studies focusing on population connectivity in centers of high biodiversity are particularly needed to protect and sustain these ecosystems in light of global climate change and increasing anthropogenic impacts from growing coastal populations and fisheries. Coral reef organisms, like anemonefishes and their host sea anemones, are ideal candidates to study the dynamics of larval dispersal, as adults are site attached and adult migration therefore does not factor in genetic mixing. The overarching aim of this thesis is to develop, test and apply molecular markers in the study of different aspects of genetic and biological diversity in anemonefishes and their obligate symbiont sea anemone partners in the Indo-Malay Archipelago, adding to the body of scientific evidence needed to support biodiversity conservation in this biodiversity hotspot . Specifically, the study furthers our understanding of connectivity in anemonefishes by presenting single species population genetic studies for, Amphiprion perideraion (Chapter I) and A. sandaracinos (Chapter II), where species specific structures are discussed in detail to highlight differences despite the highly similar life history and ecology of these fishes. This data is used as a basis for a multispecies approach to connectivity in anemonefishes by identifying and scaling regional barriers to geneflow among congeners (Amphiprion perideraion, A. sandaracinos, A. clarkii and A. ocellaris), making these results more accessible for application and implementation driven fields of research. By applying a comparative intergenomic (mitochondrial and nuclear markers) and an intrageneric (four species) approach, the mechanisms shaping genetic diversity in natural populations of anemonefishes are addressed and the variability in the system is explored.The impact of host specialization (generalist vs. specialist) and the length of the pelagic larval phase are tentatively discussed in light of the overall genetic structure that could be detected for each species. To heed the close association between anemonefishes and their sea anemone host, two mitochondrial and one nuclear marker are investigated as to their potential to delineate and identify species within the Actiniaria (Chapter III). Following a fourth research aim to study connectivity and diversity in host sea anemones, the attempted development of a set of polymorphic microsatellite loci is shown (Chapter IV)
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Molekulargenetische Untersuchungen zur Konnektivität und Evolution von Riesenmuscheln (Tridacnidae)
No full textThe Indo-West Pacific (IWP), specifically the Indo-Malay Archipelago (IMA), is known to be one of the regions exhibiting the highest marine species diversity in the world. Many hypotheses try to explain the origin of this biodiversity, mainly including the centre-of-origin, region-of-overlap, and centre-of-accumulation concepts. The IMA has a complicated geological history. Sinking sea levels during glacial periods exposed the Sunda and Sahul shelves. Therefore, the IMA provides an excellent study system for detecting the contribution of historical and ongoing processes to genetic diversity and connectivity. In addition, the Red Sea (RS) and Western Indian Ocean (WIO) are also important evolutionary centres, with many endemic species. The giant clams Tridacna crocea, T. maxima, and T. squamosa are widely distributed throughout the IWP. Their high commercial value as fishery resource and marine ornamental led to their large scale exploitation. Meanwhile, tridacnid species are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora and need urgently measures for conservation. Knowledge on genetic population structure and connectivity are important baseline data for the protection of these species, especially for the design of Marine Protected Area networks. To test if concordant barriers exist that prevent gene flow among populations and to relate this to oceanography and geological history of the IWP, the genetic population structure of the three giant clam species ranging from the RS and WIO across the Eastern Indian Ocean (EIO) and IMA to the Western Pacific (WP) and the Central Pacific (CP) were compared by using the mitochondrial cytochrome c oxidase subunit I gene (COI) as a molecular marker. The three species showed restricted gene flow and highly significant genetic structures in the area studied. The Fst-values (P < 0.001) are 0.46, 0.81, and 0.68, for T. crocea (EIO to WP), T. maxima (WIO to CP), and T. squamosa (WIO to WP), respectively. The populations could be divided into three to six groups in the different species from West to East: (1) WIO (T. maxima and T. squamosa), (2) RS (T. maxima and T. squamosa), (3) EIO (and Java Sea in T. maxima), (4) central IMA, (5) WP, and (6) CP (T. maxima). The populations in the central IMA showed panmixing. To detect the reliability of the analysis based on the mitochondrial marker, ten microsatellites were selected to study the genetic population structure of T. crocea in the IMA and the results were compared with those revealed by mtDNA. Due to the symbiotic relationship between giant clams and Symbiodinium spp. (zooxanthellae), it is difficult to isolate microsatellites. By applying a recently developed method, nine novel microsatellite markers were isolated for T. crocea and the giant clam specificity was confirmed by further test in PCRs with DNA extracts from Symbiodinium. These markers were highly polymorphic. Therefore, these microsatellites potentially provide useful nuclear markers for population genetic studies on giant clams. The genetic population structure revealed by mtDNA and nDNA (nuclear DNA) markers was congruent, with only minor difference. The correlation of genetic divergence revealed by the two marker systems was positive. Three common groups were divided as follows: (1) EIO, (2) central IMA, and (3) WP. Populations in the central IMA also showed panmixing, being well connected by currents. However, the structure revealed by microsatellite was not as strong as in the mtDNA analysis, and the genetic diversity revealed by the two genetic marker systems was different in certain populations. These minor differences might be caused by the intrinsic characteristics of mtDNA and nDNA, such as the different effective population size and mutation rate. Combination of the two marker systems might provide more information of population structure and connectivity on different temporal scales. Overall, the results showed concordant barriers for gene flow in the three species and also supported that mtDNA is applicable for population genetic analysis and recovery of connectivity in giant clams. It is suggested that sea-level changes during glacial periods, as well as oceanography are important factors that shape the genetic population structure of giant clams. The observed deep evolutionary lineages in the peripheral areas of the IMA might include cryptic species, which supports the centre-of-accumulation hypothesis that aims to explain the high diversity in the IMA. As a consequence, the information will facilitate the conservation of these endangered giant clam species. The distinct groups within each species, potentially separated Evolutionary Significant Unit, are proposed to be managed separately for their adaptive diversity; small scales MPA network should be arranged to maintain the connectivity; and restoration should be performed in areas with low genetic diversity
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