1,720,982 research outputs found
Princeton University Press, Princeton, NJ, USA, 2022, 224 pp, £25.00 (hardcover), ISBN-9780691231907
No full textTens of thousands of migrating hoverflies found dead on a strandline in the South of France
No full textKnowledge on insect migration is scattered, and we are only starting to grasp the extent and ecological impacts of their massive seasonal bioflows. Hoverflies (Diptera: Syrphidae) are one group of insects which partake in these long‐distance journeys, which are thought to have important ecological consequences including pollination, biocontrol and nutrient transfer.
Yet, few sightings of mass spring migration have been documented so far. Here, we report observations of tens of thousands of dead insects on a strandline in the South of France in mid‐May 2022.
Hoverflies represented 77% of all dead flying insects found on the strandline and most individuals belonged to the species Episyrphus balteatus and Eupeodes corollae, which are species known to exhibit migratory behaviour.
We assume that strong winds or a localised storm were the cause behind their stranding. Putative flight origins for these insects are north‐eastern Catalonia or the Balearic Islands.
This rarely documented observation enabled us to highlight the scope of hoverfly migration in spring and to discuss some of the challenges they face along their migratory route.A high number of insects were found dead on a beach in the South of France. We suspect strong winds or a localised storm were at the origin of their stranding.
All dead species recorded are known for their migratory behaviour and hoverflies made up about 77% of the dead insects.
This rarely documented observation enabled us to highlight the scope of hoverfly migration in spring and to discuss some of the challenges they face along their migratory route
Large-scale versus small-scale agriculture: Disentangling the relative effects of the farming system and semi-natural habitats on birds’ habitat preferences in the Ethiopian highlands
No full textWhile the Western World is facing an inexorable decline of its farmland biodiversity following continuous intensification of production modes, agricultural landscapes in Africa are still largely dominated by small-scale subsistence farming operated by smallholders, mostly harbouring high biodiversity. However, as most African countries are confronted to an unprecedented population growth and a rapid economic development, efforts to intensify food production are widespread, with concomitant potentially negative effects on biodiversity. We conducted a study in a highly contrasted agricultural landscape of the Ethiopian highlands comprising two distinct farming systems: large-scale farming relying on modern, combine machinery and technology (e.g. enhanced crop varieties, application of herbicides, pesticides and synthetic fertilizers) vs small-scale traditional
farming. Our objective was to disentangle the effects upon avian biodiversity of the operating farming system and the extent of semi-natural habitat features in the wider landscape. We performed a model selection approach to assess habitat selection by the overall bird community as well as the wintering, endemic and open habitat species, respectively. Our results show that habitat preferences of birds in the Ethiopian highlands were mainly driven by the amount of semi-natural habitats within the landscape, with varying effects depending on the farming system itself. While large-scale farming had overall more negative effects on birds, some typical open habitat species were mostly restricted to these wide-open landscapes. Our findings thereby suggest that both farming systems could coexist as long as semi-natural habitats are preserved and agricultural management maintained in its current practices. We emphasize the urgent need to conduct further studies integrating the socio-economic aspects in order to better predict future impacts of agricultural intensification processes on
African farmland biodiversity
High semi‐natural vegetation cover and heterogeneity of field sizes promote bird beta‐diversity at larger scales in Ethiopian Highlands
Full text link1. The intensification of farming practices exerts detrimental effects on biodiver-
sity. Most research has focused on declines in species richness at local scales
(alpha-diversity) although species loss is exacerbated by biotic homogenization
that operates at larger scales (i.e. affecting beta-diversity). The majority of stud-
ies have been conducted in temperate, industrialized countries while tropical
areas remain poorly studied. Agricultural landscapes of sub-Saharan Africa are
still largely dominated by small-scale subsistence farming, but strenuous efforts
to intensify farming practices are currently spreading to meet a growing food
demand. It is therefore crucial to understand how these intensified practices
affect biodiversity to mitigate their negative impacts.
2. We investigated how farming system (small- vs. large-scale farming) and land-
scape complexity (semi-natural vegetation cover) drive bird species composi-
tion, community turnover and beta-diversity patterns in Ethiopian Highlands'
agroecosystems. We evaluated the following hypotheses: (1) large-scale farm-
ing homogenizes bird communities, (2) community turnover is higher in small-
scale farms, (3) interactive effects between landscape complexity and farming
systems shape avian communities and (4) heterogeneity of field sizes increases
community turnover at larger scales.
3. Bird communities underwent greater compositional changes along the land-
scape complexity than along the agricultural intensity gradient. Contrary to
our expectations, beta-diversity was not significantly lower within large-scale
farms (no biotic homogenization), and complex landscapes that still offer a high
amount of semi-natural vegetation promoted community turnover in both farm-
ing systems.
4. Semi-natural vegetation cover mediated how avian communities responded to
agricultural intensification: the compositional differences between small- and large-scale farms increased with vegetation cover, further promoting avian com-
munity heterogeneity at the landscape level.
5. The heterogeneity in field sizes also enhanced bird community turnover, sug-
gesting that a combination of both small- and large-scale farming systems within
a given landscape unit would promote beta-diversity at larger scales, provided
large-scale farms do not become dominant.
6. Synthesis and applications. Landscape complexity shaped avian communities to
a stronger degree than farming intensity, emphasizing the importance of semi-
natural vegetation and landscape heterogeneity for the maintenance of diverse
bird communities and for achieving multifunctional landscapes promoting biodi-
versity and associated ecosystem services on the High Ethiopian plateaus
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
) in its prime wintering grounds, the cereal‐dominated Ethiopian Highlands
Full text linkAbstract
Agricultural intensification and land-use changes are major factors impacting farmland biodiversity. The Ortolan Bunting Emberiza hortulana is the long-distance trans-Saharan migratory passerine that has undergone the most dramatic decline among all European farmland birds. The factors responsible for this decline may originate from the breeding grounds, migration stopovers and/or overwintering quarters. Very little is known about conditions on the species' wintering grounds, but a recent study has highlighted the utmost importance of the traditionally managed agroecosystems in the Ethiopian Highlands as a key wintering area, apparently harbouring as much as 90% of the world's Ortolan Bunting population. Using radiotracking and line transect surveys, this study aimed to provide fine-grained information about species–habitat relationships in the Ortolan Bunting overwintering quarters. Our results showed the importance, at the landscape scale, of small-scale agriculture, notably of traditionally managed, cereal-dominated fields interspersed with semi-natural structures. At a foraging-site scale, on the other hand, patches of bare ground in combination with large areas of post-harvesting stubble represented key habitat features. Stubbles provide an essential food resource and bare ground promotes ground foraging by enhancing food accessibility. The maintenance of a traditional agricultural economy will be essential to maintain the habitat potential for the Ortolan Buntings overwintering in the Ethiopian Highlands and will be instrumental in preserving its world population from further decline
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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