1,720,985 research outputs found
Fine-scale biogeographical boundary delineation and sub-population resolution in the Symbiodinium thermophilum Coral Symbiont group from the persian/Arabian Gulf and Gulf of Oman
No full textThe adaptation of tropical coral communities to the world's hottest sea, the Persian/Arabian Gulf (PAG), has recently been associated with ecological selection acting on a group of coral-associated algal symbionts, the Symbiodinium thermophilum group. Previous studies have shown that considerable genetic diversity exists within the group and that group members found within the PAG are significantly differentiated from those found externally, in the Gulf of Oman and wider waters. However, little is known about this genetic diversity. As an initial step towards understanding whether this diversity could represent niche adapted, selectable populations within the S. thermophilum group that may act as natural sources of stress tolerant associations to Indo-Pacific reefs, we investigate whether the diversity is structured between populations and where the location of the internal-external genetic partition lies. We use regions of the nuclear ribosomal DNA (ITS1-5.8S-ITS2) and chloroplastic psbA gene (non-coding region) from > 100 S. thermophilum group-harbouring Porites spp. (P. lobata, P. lutea, and P. harrisoni) sampled across steep temperature and salinity gradients to conduct analyses of variance and create maximum parsimony networks to assess genetic structure and (dis)similarity within and between populations of S. thermophilum found within the PAG and externally in the Gulf of Oman. Our analyses resolve a sharp genetic boundary between Symbiodinium populations in the western Strait of Hormuz and identify significant genetic structure between populations with as little as 20 km between them demonstrating that differentiation between populations is likely due to factors other than limited connectivity. Further, we hypothesize that genotypes identified outside of the PAG in the Gulf of Oman existing in near-oceanic salinities, yet thermally challenging waters, putatively represent candidates for stress-tolerant symbionts that could act as natural seed populations of stress tolerant genotypes to the wider indo-Pacific.</p
Symbiodinium thermophilum symbionts in Porites harrisoni and Cyphastrea microphthalma in the northern Persian Gulf, Iran
No full textCoral communities of the Persian Gulf (PG) withstand maximum and annual ranges of water temperatures that surpass those found on the majority of reefs elsewhere. As such, these communities may inform on how coral reefs might adapt to the warmer waters of the future. Depending on the algal symbiont (genus Symbiodinium) harboured, advantages in stress tolerance may be conferred to the coral holobiont. Characterizing the algal component is therefore critical in determining the coral holobiont's tolerance phenotype. Coral associations off the Arabian coastline of the PG have been characterized as biogeographically unique, containing a rare group of taxonomically ancestral and thermotolerant algal symbionts, the Symbiodinium thermophilum group. In contrast, waters off the Iranian coast remain poorly characterized with a notable lack of S. thermophilum group symbionts identified in coral associations to date. Here, we characterize the algal component of two reef building corals (Porites harrisoni and Cyphastrea microphthalma) predominant at three sites spanning almost the entire length of the PG's Iranian coast. Genotyping using the chloroplastic 23S and nuclear ITS2 genes, we demonstrate the presence of S. thermophilum group symbionts. We discuss the probable physical drivers of these associations and highlight the need for further research in these relatively understudied waters.<br/
Validation of the binary designation Symbiodinium thermophilum (Dinophyceae)
No full textThe binary designation Symbiodinium thermophilum was invalid due to the absence of an illustration as required by Article 44.2 of the ICN. Herein, it is validated. This species is the most common symbiont in reef corals in the southern Persian/Arabian Gulf, the world's hottest body of water sustaining reef coral growth.</p
Ancestral genetic diversity associated with the rapid spread of stress-tolerant coral symbionts in response to Holocene climate change
No full textCoral communities in the Persian/Arabian Gulf (PAG) withstand unusually high salinity levels and regular summer temperature maxima of up to ?35 °C that kill conspecifics elsewhere. Due to the recent formation of the PAG and its subsequent shift to a hot climate, these corals have had only <6,000 y to adapt to these extreme conditions and can therefore inform on how coral reefs may respond to global warming. One key to coral survival in the world’s warmest reefs are symbioses with a newly discovered alga, Symbiodinium thermophilum. Currently, it is unknown whether this symbiont originated elsewhere or emerged from unexpectedly fast evolution catalyzed by the extreme environment. Analyzing genetic diversity of symbiotic algae across >5,000 km of the PAG, the Gulf of Oman, and the Red Sea coastline, we show that S. thermophilum is a member of a highly diverse, ancient group of symbionts cryptically distributed outside the PAG. We argue that the adjustment to temperature extremes by PAG corals was facilitated by the positive selection of preadapted symbionts. Our findings suggest that maintaining the largest possible pool of potentially stress-tolerant genotypes by protecting existing biodiversity is crucial to promote rapid adaptation to present-day climate change, not only for coral reefs, but for ecosystems in general
Local adaptation constrains the distribution potential of heat-tolerant Symbiodinium from the Persian/Arabian Gulf
No full textThe symbiotic association of corals and unicellular algae of the genus Symbiodinium in the southern Persian/Arabian Gulf (PAG) display an exceptional heat tolerance, enduring summer peak temperatures of up to 36?°C. As yet, it is not clear whether this resilience is related to the presence of specific symbiont types that are exclusively found in this region. Therefore, we used molecular markers to identify the symbiotic algae of three Porites species along >1000?km of coastline in the PAG and the Gulf of Oman and found that a recently described species, Symbiodinium thermophilum, is integral to coral survival in the southern PAG, the world’s hottest sea. Despite the geographic isolation of the PAG, we discovered that representatives of the S. thermophilum group can also be found in the adjacent Gulf of Oman providing a potential source of thermotolerant symbionts that might facilitate the adaptation of Indian Ocean populations to the higher water temperatures expected for the future. However, corals from the PAG associated with S. thermophilum show strong local adaptation not only to high temperatures but also to the exceptionally high salinity of their habitat. We show that their superior heat tolerance can be lost when these corals are exposed to reduced salinity levels common for oceanic environments elsewhere. Consequently, the salinity prevailing in most reefs outside the PAG might represent a distribution barrier for extreme temperature-tolerant coral/Symbiodinium associations from the PAG
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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