1,721,046 research outputs found
Drywood Termites (Kalotermitidae)
No full textThe term drywood termites was introduced for those species nesting and feeding in wood with low or no moisture. The term is used as a synonym for the family Kalotermitidae, although not all kalotermitids exhibit the same substrate prefer- ence. There are, in fact, many species living in rotten or damp wood logs (such as Neotermes). Kalotermitidae are placed among the lower ter- mites, a paraphyletic group that includes early- branching termite lineages and is characterized by the presence of symbiotic flagellates in their gut
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
The evolution of metazoan genomes and highly conserved SINE domains (51881)
No full textShort interspersed elements (SINEs) are non-autonomous retrotransposons with modular structures: a small RNA-related head, a body and an AT-rich tail. Despite their high turnover rate and de novo emergence, the body may retain highly conserved domains (HCD) among different SINE families: in metazoan, up to seven HCD-SINEs have been recognized. Interestingly, two HCD-SINEs (CORE- and Deu-SINEs) have been repeatedly subject to exaptation in mammalian genomes, becoming part of gene regulatory networks. Analyzing molluscan transcriptomes and genomic sequences we characterized four new HCD-SINE families, whose insertion site analyses suggest recent activity. Two HCDs were previously found in chordates' SINEs: the V-domain (here found in gastropods, bivalves and chitons), and the CORE-domain (here found in bivalves and gastropods). A CORE-SINE has been further identified in the horseshoe crab and one more family isolated in snails retains the cephalopods’ Ceph domain. Tracking the ancestry of HCDs in the metazoan phylogeny revealed that some of them date back to the Radiata-Bilateria and the Protostomia- Deuterostomia splits. We suggest that the evolutionary conservation of HCD may account for the high SINE diversity (“module exchange” model) and for their long-term inheritance in metazoan genomes
L'analyse phylogénétique des termites du genre Reticulitermes suggère trois acquisitions indépendantes de l'AQS (Asexual Queen Succession)
No full textDans le genre Reticulitermes (Rhinotermitidae), il a été mis en évidence un système de reproduction particulier appelé ‘Asexual Queen Succession' (AQS). Dans ce système, les œufs fertilisés pondus par la reine primaire peuvent se développer en mâles ou femelles de toutes les castes, à l'exception des femelles néoténiques qui se développent à partir d'œufs non-fertilisés (parthénogenèse thélytoque). Dépourvus d'ailes, ces femelles néoténiques demeurent dans la colonie parentale où elles se reproduiront avec le mâle primaire, ou avec des mâles néoténiques issus de la reproduction sexuée des primaires.
Sur les 9 espèces de Reticulitermes étudiées, l'AQS a été détecté à ce jour chez 3 d'entre elles. Il est intéressant de constater que les espèces exprimant l'AQS ne sont pas des espèces proches au sein du genre. Afin de tester l'hypothèse selon laquelle l'AQS a évolué indépendamment dans le genre Reticulitermes, nous avons conduit des analyses phylogénétiques du genre basées sur 61 taxons et 5 marqueurs moléculaires (3 régions mitochondriales et 2 nucléaires). Les résultats suggèrent fortement que l'AQS a été acquis au moins trois fois indépendamment dans le genre. Cette étude a également permis de préciser l'origine spatio-temporelle des Reticulitermes et leur pattern de diversification
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
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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