1,721,177 research outputs found
Changes in host-parasitoid food web structure with elevation
No full textGradients in elevation are increasingly used to investigate how species respond to changes in local climatic conditions. Whilst many studies have shown elevational patterns in species richness and turnover, little is known about how food web structure is affected by elevation.Contrasting responses of predator and prey species to elevation may lead to changes in food web structure. We investigated how the quantitative structure of a herbivore‐parasitoid food web changes with elevation in an Australian subtropical rain forest.On four occasions, spread over 1 year, we hand‐collected leaf miners at twelve sites, along three elevational gradients (between 493 m and 1159 m a.s.l). A total of 5030 insects, including 603 parasitoids, were reared, and summary food webs were created for each site. We also carried out a replicated manipulative experiment by translocating an abundant leaf‐mining weevil Platynotocis sp., which largely escaped parasitism at high elevations (≥900 m a.s.l.), to lower, warmer elevations, to test if it would experience higher parasitism pressure.We found strong evidence that the environmental change that occurs with increasing elevation affects food web structure. Quantitative measures of generality, vulnerability and interaction evenness decreased significantly with increasing elevation (and decreasing temperature), whilst elevation did not have a significant effect on connectance. Mined plant composition also had a significant effect on generality and vulnerability, but not on interaction evenness. Several relatively abundant species of leaf miner appeared to escape parasitism at higher elevations, but contrary to our prediction, Platynotocis sp. did not experience greater levels of parasitism when translocated to lower elevations.Our study indicates that leaf‐mining herbivores and their parasitoids respond differently to environmental conditions imposed by elevation, thus producing structural changes in their food webs. Increasing temperatures and changes in vegetation communities that are likely to result from climate change may have a restructuring effect on host–parasitoid food webs. Our translocation experiment, however, indicated that leaf miners currently escaping parasitism at high elevations may not automatically experience higher parasitism under warmer conditions and future changes in food web structure may depend on the ability of parasitoids to adapt to novel hosts
Host-plants of leaf-miners in Australian subtropical rainforest
No full textLeaf-miners are endophytic insect herbivores that are considered to be relatively host-specific compared with other types of insect herbivores, often depending on one or a few congeneric hosts. Because of their degree of host-specificity, they may be particularly vulnerable to environmental change. Despite this, little is known about the host-plants and life histories of the Australian leaf-mining fauna. Here we present new information on the host-plant use of leaf-miners occurring in Australian subtropical rainforest. We repeatedly hand-collected leaf-miners at 14 sampling sites in the ‘Tweed Caldera’ subtropical rainforest region of south-eastern Queensland and north-eastern New South Wales, Australia. Leaf-miners and their host-plants were identified to species (or morphospecies in the case of some leaf-miners). Within the region, a total of 106 plant species was recorded as leaf-miner hosts, on which a total of 12 679 individual leaf-miners was counted, belonging to 50 different species. We measured the local host-plant range of each leaf-miner species for which we had reliable incidence records across sampling sites (24 species). Local host-specificity was relatively high with 66.7 % of species recorded from a single or two congeneric host-plants. 16.7 % of species were restricted to a single plant family and 16.7 % were recorded on a few to several plants of the same plant order or across a range of unrelated host-plants
Elevational turnover in the composition of leaf-miners and their interactions with host plants in Australian subtropical rainforest
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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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The Scribbly Gum Moths: <i>Ogmograptis</i> species
No full textUnusually for an iconic animal, the scribbly gum moths (Ogmograptis spp. Bucculatricidae) are better known for the distinctive tracks they leave. Larvae feed in the phellogen, or cork cambium, of Eucalyptus bark. It is only months later, when a bark layer sheds, that their larval mines are revealed, appearing as if someone has scribbled on the trunk. The scribbles, an accurate record of larval behaviour of some species, have distinct attributes on different host tree species. Considered monotypic for over 75 years, there are now 12 Ogmograptis species described. Larval behaviour is best understood for the ‘scribula’ group which consists of O. scribula, O. fraxinoides, O. racemosa and O. pilularis. The potential distribution of the scribbly gum moths is indicated by records of the moths themselves and their eucalypt hosts. The life history of Ogmograptis species is described, where known, with an emphasis on bark traits which could explain why only some Eucalyptus are hosts for Ogmograptis species and how larvae identify the bark layer in which to mine. Increases in temperature and fire frequency/severity as climate shifts, together with habitat destruction, are concerning threats to scribbly gum moths
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