1,720,956 research outputs found
Reproductive strategies and breeding systems in Reticulitermes subterranean termites (Isoptera, Rhinotermitidae)
No full textTermites are eusocial insects that live in colonies characterized by cooperative behavior, where most individuals forego their own reproduction and help to raise the offspring of a few nest members. This may impact on the colony abilities to adapt and exploit the environment. In subterranean termites of the genus Reticulitermes, a new colony is settled by a single, heterosexual pair of winged individuals (primary reproductives; kings and queens); as colony maturate and/or upon founders death, neotenics (secondary reproductive; SRs) develop and contribute to offspring production. This leads to inbreeding as SRs are genetically related. In some species, including the Italian R. lucifugus, primary queens produce secondary queens by parthenogenesis (P); then, secondary queens will mate with the primary king extending the genetic contribution of the primary queen through time (Asexual Queen Succession, AQS), eventually helping to avoid inbreeding. As a consequence of the increasing genetic contribution of the primary queen, AQS colonies show a female-biased sex ratio of winged reproducers. Here we present population genetics and sex ratio analyses of R. lucifugus, and compare results with data on two other species: R. flavipes and R. grassei. Genetic data indicated the presence of AQS in R. lucifugus and its absence in the other two species, accordingly to winged sex ratio observations. Data confirmed that P occurs through a mechanism of terminal fusion. Moreover, winged reproductives resulted all produced by amphigony, confirming that P is only used for secondary queen production. Finally, morphometric and biomass analyses performed on R. lucifugus winged reproductives suggested a larger investment in female sex in AQS colonies. The AQS system has been observed to be scattered among termites, occurring through different mechanisms and leading to different outcomes. This variability still need to be explained in the light of social behavior evolution
Phylogeography of European dry-wood dwelling termites of the genus Kalotermes (Isoptera, Kalotermitidae).
No full textThe only native European dry-wood termites belong to the genus Kalotermes. Until recently, these termites were thought to belong to a single species, Kalotermes flavicollis. However, recent studies described two new species: K. italicus (Italy) and K. phoenicae (Cyprus, Middle-East). Moreover, molecular phylogenetic studies revealed divergent K. flavicollis sublineages in Corse-Sardinia and Southern France. As such lineages have been shown to frequently merge in same colonies, it is important to better understand the evolution of this genus in Europe. To widen the analyses on Kalotermes phylogeography, 22 colonies collected in 11 European localities were analyzed together with those obtained from previous studies, sequencing 912 bp of the mitochondrial genome (COI/tRNA-Leu/COII) in two individuals/colony. Phylogenetic analyses indicate that (i) K. italicus spreads from Central Italy to South France, (ii) the Corse- Sardinian lineage can also be found in the Italian peninsula, and (iii) the Southern France lineage extends to the Iberian peninsula. A time-calibrated phylogeny, computed on two mitochondrial markers (COI/tRNA- Leu/COII; 16S) on representative samples, showed that (i) extant European Kalotermes started differentiating ~32 Myr ago, with the separation of K. phoenicae; (ii) K. italicus and K. flavicollis split ~15 Myr ago; (iii) K. flavicollis sublineages diverged during and after the Messinian salinity crisis, ~6 Myr ago. Another European termite genus, Reticulitermes, comprises in the same area seven species/subspecies and all taxa showed marked intraspecific differentiation. Interestingly, recent analyses indicated that Reticulitermes differentiated in half time with respect to Kalotermes. The different nesting ecology and/or habitat constraints may explain this significant difference
Genetic analysis reveals multiple introduction events of the Balkanic Reticulitermes urbis (Blattodea,Termitoidae, Rhinotermitidae) in Italy and France.
No full textBiological invasions are a key factor in the ecological changes, and social insects are among the most successful invasive animals. Phylogeography and population genetics can provide detailed information on the introduction routes and invasion biology. Reticulitermes urbis is a subterranean termite native of Balkan Peninsula and introduced in Southern France and Eastern Italy. Introductions in these countries probably resulted from anthropic activities and invasive populations currently live in both forests and urban areas. To identify the source population and to infer the minimum number of introductions, we analyzed mitochondrial (COII) and nuclear (6 microsatellites) loci on 7 native and 39 introduced colonies (15 from France; 24 from Italy). Mitochondrial analysis confirmed the presence of two major lineages in which native and introduced populations cluster together, irrespective of the sampling area (native or invasive range). Microsatellite loci analysis identified two genetic clusters, each including individuals from both native and introduced samples. Moreover the analysis of molecular variance evidenced very low genetic differentiation between the three considered areas (native, French or Italian range). Finally, data showed that introduced populations are less variable in both mitochondrial and nuclear markers, suggesting that introductions might have induced a loss of genetic diversity. On the whole, results supported multiple introductions into the two invasive ranges of France and Italy. This is consistent with links between native and invasive areas protracted in time, as expected in cases of human trades routes. Historical data of human settlement and kingdoms might provide explanations for R. urbis modern distribution
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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