1,721,021 research outputs found
Trends in hydroidomedusan research from 1911 to 1997
Full text linkThe papers on hydroidomedusae published from 1911 to 1997 total 10,934. They have been assigned to the following categories: faunistics and systematics; sub-organismal biology; ecology; evolution; life cycles; paleontology. The general trend, comprising all papers, can be divided into four time intervals: the first (1911-1939) with an average of sixty papers/year and with a slight decrease due to First World War; the second one (1940-1947), with an average of 38 papers/year, marked by a dramatic decrease coinciding with Second World War; the period 1948-1991 shows a steady increase until the mid-Seventies, when a small decrease occurred, followed by an increasing trend reaching its apex in the late Eighties-early Ninenties with a record of 296 papers in 1991 and with an average of 175 papers/year; the period 1992 1997, with an average of 178 papers/year, is marked by a sharp decrease, reaching the values of the mid Sixties. The most important category in terms of number of papers is sub-organismal biology, followed by faunistics and systematics. Systematic studies dictated the trend in the first decades of the century, whereas sub-organismal ones are prevalent from the Sixties onwards. Faunistic and systematic-taxonomic papers have a steady trend of production, with just a slight decrease over these last years. The formerly leading countries in systematics (UK, USA, France) are now almost inactive in this discipline, whereas countries with little or no tradition in this field (such as Spain) are taking the leadership
Who cares about the Hydrozoa of the Mediterranean Sea? An essay on the zoogeography of inconspicuous groups
No full textThe Messininan crisis, 5 MY before present, marked the recent history of the Mediterranean Sea. The opening of Gibraltar, and the inflow of Atlantic water, brought in the ancestors of the species that inhabit the Mediterranean today. The opening of the Suez Canal allowed the entrance of Indo-Pacific species. Ships and aquacuhure transported species from all over the world. At present, the Mediterranean Sea is a melting pot of a blend of biota that probably has no equivalent in any other part of the world. The tropicalisation of the Mediterranean and Lessepsian migration are conductive to the establishment of tropical species into the basin, with some outstanding examples like that of Caulerpa species, and of the scyphomedusa Rhopilema nomadica. At present, the arrival of new conspicuous species is well monitored and researchers are ready to publish new records of recognisable species. These usually belong to popular groups such as fish. molluscs and decapod crustaceans, or to groups that cannot pass unnoticed due to a marked attitude to form outbreaks, like dinoflagellates or scyphozoan jellyfish and ctenophores. What about the other groups? The bulk of biodiversity, in terms of species numbers, is made of poorly known and inconspicuous species that, usually, can be noticed only by specialised taxonomists. Taxonomy is disappearing front most scientific communities, so that our appreciation of biodiversity is being biased towards conspicuous groups. The Hydrozoa are taken as an example of inconspicuous group whose knowledge has greatly progressed in the last decades due to the presence of some specialists in the Mediterranean area. The number of species recorded from the Mediterranean almost doubled in thirty years and the number of new records is still increasing. The ecological role of these animals, especially those represented also by a medusa stage, can be great due to their general ability to feed upon fish eggs and larvae and/or on the plankton that fish larvae feed upon, so acting as potential predators and/or competitors of commercial species. They might even be keystone predators, depressing potentially monopolising fish species, so leaving space for less competitive species. Neglecting this component of biodiversity might lead to ecological misunderstandings that, in their turn, might lead to misleading interpretations of the causes affecting the yield of fisheries. The main question arising from the example of the Hydrozoa is: are conspicuous groups sufficient to appreciate marine biodiversity and understand its functioning? The answer deriving from the example of the Hydrozoa is: No
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
The Mediterranean in check: Biological invasions in a changing sea
Full text linkIn recent decades, the high introduction rate of alien species (AS) has been mainly due to the increasingly widespread human movements, which often compromise natural barriers, facilitating the invasion of new geographic areas and environments. Being completely new in the recipient habitat, alien invasive species can often have strongly negative impacts on native communities, sometimes causing substantial and irreversible ecological and economic damage. Thus, AS have been branded as “negative” and are often targeted for eradication. However, an accurate assessment of ecological and economic impacts of alien taxa is still lacking in many species, and this is particularly true in marine environments. We focused on the Mediterranean Sea, a very important marine biodiversity “hot spot,” which is among the areas that have been most influenced by the arrival of non-native species, a process also linked to global warming, leading to a deep transformation of this basin. We describe both negative and positive aspects of some well-known introductions, assuming a different view of conservation. Biological invasions are, in fact, a fundamental and integral aspect of nature that has always been present in the history of life on Earth. Imagining that nature is static and needs to be restored to a particular state is not a reasonable way of looking at the processes of life. With this in mind, we argue that defining priorities in management and conservation is a prerogative that should not be based on the containment/eradication of one or another species, but on the conservation of those environmental conditions that are essential for the proper functioning of ecosystems. In other words, native versus non-native species distinction cannot be the main guiding principle in conservation and restoration. For this reason, great attention must be paid to the containment of those human activities that cause greater pollution and rapid changes, and therefore threaten the habitats and biodiversity that we care about most
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
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