1,720,985 research outputs found
Molecular systematics and origin of the Mediterranean sea rock-pool mosquitoes of the aedes mariae (diptera: culicidae) complex
No full textMosquitoes belonging to the Aedes mariae complex, including Aedes mariae (Sergent & Sergent), Aedes zammitii (Theobald), and Aedes phoeniciae (Coluzzi & Sabatini), are among the few animals
inhabiting the extreme habitat of sea rock pools. Morphological analysis of these species and crossing experiments conducted in laboratory and natural conditions inferred the occurrence of three taxa
with a parapatric distribution along the coasts of the Mediterranean Basin. To date, however, genetic characterization of the three species within the Ae. mariae complex and an assessment of their interspecific
differentiation are lacking. In this study, we used both nuclear (i.e., 14 allozymic loci) and mitochondrial genetic markers (i.e., sequences of the cytochrome oxidase I and II genes) to genetically
characterize the three species belonging to the complex. Then, we used mitochondrial markers to inferphylogenetic relationships between the species and estimate the time to most recent common ancestor
(TMRCA). The allozymic and mitochondrial markers showed the occurrence of three distinct gene pools, namely, Ae. mariae, Ae. zammitii, and Ae. phoeniciae. The TMRCAs for the entire in-group were
estimated to have occurred during the early Pleistocene (i.e., mean node age of 1.739 million years ago). An important role of Pleistocene climatic changes could be suggested in the origin of the species of the Ae. mariae complex and in shaping their pattern of intraspecific genetic diversit
Dynamics of mtDNA introgression during species range expansion. Insights from an experimental longitudinal study
Full text linkIntrogressive hybridization represents one of the long-lasting debated genetic consequences of species range expansion. Mitochondrial DNA has been shown to heavily introgress between interbreeding animal species that meet in new sympatric areas and, often, asymmetric introgression from local to the colonizing populations has been observed. Disentangling among the evolutionary and ecological processes that might shape this pattern remains difficult, because they continuously act across time and space. In this context, long-term studies can be of paramount importance. Here, we investigated the dynamics of mitochondrial introgression between two mosquito species (Aedes mariae and Ae. zammitii ) during a colonization event that started in 1986 after a translocation experiment. By analyzing 1,659 individuals across 25 years, we showed that introgression occurred earlier and at a higher frequency in the introduced than in the local species, showing a pattern of asymmetric introgression. Throughout time, introgression increased slowly in the local species, becoming reciprocal at most sites. The rare opportunity to investigate the pattern of introgression across time during a range expansion along with the characteristics of our study-system allowed us to support a role of demographic dynamics in determining the observed introgression pattern
Cannibalism and Necrophagy Promote a Resource Loop and Benefit Larval Development in Insects of Temporary Waters
Full text linkTemporary aquatic habitats are contingent on the allochthonous inputs of plant and animal detritus, whose quality and availability can significantly affect the species developing in these habitats. Although animal detritus (i.e., invertebrate carcasses) is a high-quality food, it is an unpredictable and variable resource. On the contrary, conspecific individuals (dead or alive) are a nutritionally high-quality food source that is always available. In this context, conspecifics consumption, by cannibalism or necrophagy, can be a good strategy to overcome nutrient limitation and allow individual maintenance and development. Here, we tested this hypothesis by using the tiger mosquito Aedes albopictus. By carrying out laboratory and semi-field experiments, we first estimated the relative rate of cannibalism and necrophagy, under different larval densities. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that cannibalism and necrophagy occurred under all experimental conditions, and that conspecific consumption had positive effects on individual development, as it significantly increased the rate of adult emergence and larval survival. Interestingly, about 50% of the initial cohort was consumed by conspecifics, suggesting that cannibalism and necrophagy can drive an important resources loop in temporary aquatic habitats
Per una tassonomia delle occorrenze omometriche nei canti strofici di Sofocle
No full textTra gli strumenti a disposizione del poeta greco, figurano le occorrenze omometriche, forme di coincidenza metrico-verbale che, nell’identità della collocazione metrica in una struttura strofica, nascondono l’intenzione autoriale di un potenziamento della dimensione semantica dell’ode attraverso l’abile sfruttamento dei meccanismi della ripetizione. Nelle composizioni sofoclee, all’obiettivo primario di dimostrarne l’attinenza con l’azione drammatica in svolgimento si sommano altre specializzazioni d’uso che, mentre potrebbero evidenziare il ruolo attoriale attivo della compagine corale, invitano a un’attenta riflessione di ordine tassonomico che colga le plurime sfumature di uno strumento, la cui applicazione offre un ulteriore mezzo per l’esegesi e la profonda comprensione del prodotto poetico antico.Among the instruments at the Greek poet's disposal are homometrical occurrences, forms of metric-verbal coincidence that, in the identity of the metrical collocation in a strophic structure, conceal the authorial intention of an enhancement of the semantic dimension of the ode through the skilful exploitation of the mechanisms of repetition. In the Sophoclean compositions, the primary objective of demonstrating their relevance to the dramatic action in progress is compounded by other specialisations of use that, while they may highlight the active acting role of the choral ensemble, invite a careful reflection of a taxonomic order that grasps the multiple nuances of an instrument, the application of which offers a further means for the exegesis and profound understanding of the ancient poetic product
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
Glacial History of a Modern Invader: Phylogeography and Species Distribution Modelling of the Asian Tiger Mosquito Aedes albopictus
No full textBackground: The tiger mosquito, Aedes albopictus, is one of the 100 most invasive species in the world and a vector of human diseases. In the last 30 years, it has spread from its native range in East Asia to Africa, Europe, and the Americas. Although this modern invasion has been the focus of many studies, the history of the species' native populations remains poorly understood. Here, we aimed to assess the role of Pleistocene climatic changes in shaping the current distribution of the species in its native range. Methodology/Principal Findings: We investigated the phylogeography, historical demography, and species distribution of Ae. albopictus native populations at the Last Glacial Maximum (LGM). Individuals from 16 localities from East Asia were analyzed for sequence variation at two mitochondrial genes. No phylogeographic structure was observed across the study area. Demographic analyses showed a signature of population expansion that started roughly 70,000 years BP. The occurrence of a continuous and climatically suitable area comprising Southeast China, Indochinese Peninsula, and Sundaland during LGM was indicated by species distribution modelling. Conclusions/Significance: Our results suggest an evolutionary scenario in which, during the last glacial phase, Ae. albopictus did not experience a fragmentation phase but rather persisted in interconnected populations and experienced demographic growth. The wide ecological flexibility of the species probably played a crucial role in its response to glacial-induced environmental changes. Currently, there is little information on the impact of Pleistocene climatic changes on animal species in East Asia. Most of the studies focused on forest-associated species and suggested cycles of glacial fragmentation and post-glacial expansion. The case of Ae. albopictus, which exhibits a pattern not previously observed in the study area, adds an important piece to our understanding of the Pleistocene history of East Asian biota
HYBRIDIZATION, NATURAL SELECTION, AND EVOLUTION OF REPRODUCTIVE ISOLATION: A 25-YEARS SURVEY OF AN ARTIFICIAL SYMPATRIC AREA BETWEEN TWO MOSQUITO SIBLING SPECIES OF THE Aedes mariae COMPLEX
No full textNatural selection can act against maladaptive hybridization between co-occurring divergent populations leading to evolution of reproductive isolation among them. A critical unanswered question about this process that provides a basis for the theory of speciation by reinforcement, is whether natural selection can cause hybridization rates to evolve to zero. Here, we investigated this issue in two sibling mosquitoes species, Aedes mariae and Aedes zammitii, that show postmating reproductive isolation (F1 males sterile) and partial premating isolation (different height of mating swarms) that could be reinforced by natural selection against hybridization. In 1986, we created an artificial sympatric area between the two species and sampled about 20,000 individuals over the following 25 years. Between 1986 and 2011, the composition of mating swarms and the hybridization rate between the two species were investigated across time in the sympatric area. Our results showed that A. mariae and A. zammitii have not completed reproductive isolation since their first contact in the artificial sympatric area. We have discussed the relative role of factors such as time of contact, gene flow, strength of natural selection, and biological mechanisms causing prezygotic isolation to explain the observed results
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