1,721,068 research outputs found
Seirophora villosa (Ach.) Frödén: a multidisciplinary investigation on morphology, ecophysiology and ecology
No full textQuesto progetto mira a studiare l’ecologia e la fisiologia di Seirophora villosa (Ach.) Frödén, specie epifita ritenuta in via di regressione a causa di una sempre più avanzata frammentazione del suo habitat preferenziale, il ginepreto costiero, habitat prioritario secondo la Direttiva 92/43 CEE (2250* “Dune costiere con Juniperus spp.”). La degradazione e la perdita dell’habitat in effetti sono ritenute le principali cause del declino delle popolazioni di S. villosa e recenti studi hanno evidenziato una correlazione positiva fra superficie locale dell’habitat e abbondanza di S. villosa. Tuttavia è stato dimostrato che, anche in situazioni ottimali, S. villosa non occupa tutto l’areale disponibile suggerendo una possibile implicazione di fattori ecologico/biologici limitanti la sua dispersione.
Da queste considerazioni nasce questa ricerca che si propone di indagare sia a livello di popolazione che di individuo le caratteristiche che determinano la distribuzione di questa specie. Per raggiungere questi obiettivi abbiamo proceduto sia con esperimenti in campo che in laboratorio.
In campo sono state valutate le relazioni che intercorrono fra le variabili strutturali del ginepreto e la diversità funzionale e specifica delle comunità licheniche epifite che lo ospitano e in particolare la relazione fra struttura dell’habitat e presenza di S. villosa.
In laboratorio, sono stati indagati gli effetti delle principali variabili ecologiche sulla eco-fisiologia della specie al fine di caratterizzarne la nicchia ecologica. Abbiamo valutato le risposte fisiologiche della specie a cambiamenti di disponibilità della risorsa idrica e luminosa, in relazione alla dimensione dei talli. Inoltre, abbiamo indagato su di un carattere morfologico peculiare di questa specie, la pelosità del tallo, ipotizzando che questo carattere ricopra un ruolo primario nelle performance eco-fisiologiche della specie. Per indagare su questo aspetto abbiamo investigato eventuali meccanismi biochimici e fisiologici che la specie mette in atto per rispondere ed adattarsi alla presenza/assenza del pelo in superficie durante un ciclo di disidratazione e in presenza di stress salino.
I risultati ottenuti dagli esperimenti a livello di popolazione mostrano che effettivamente un ginepreto continuo e strutturato porta ad una varietà e stabilità di microhabitat che supporta una forte differenziazione floristica e funzionale della comunità lichenica che lo ospita. Per quanto riguarda S.villosa, i nostri risultati confermano gli studi pregressi, evidenziando che le pratiche conservazionistiche per questa specie devono essere estese ad una scala ridotta, a livello di albero. I risultati di laboratorio mostrano che le dimensioni dei talli influiscono sulla capacità di ritenzione idrica dei questa specie; i campioni di S.villosa sono suscettibili ad una forte radiazione luminosa in particolare se questa è protratta nel tempo, in particolare i talli più piccoli che una volta fotoinibiti manifestano un’abilità di recupero piuttosto ridotta. Inoltre, i risultati confermano le nostre ipotesi a presenza dei peli sul tallo di S.villosa è risultato essere un tratto morfologico strategico per le performances di questa specie. La presenza del pelo offre un meccanismo passivo ma selettivo dell’acqua, regolandone l’assorbimento e la repulsione. Allo stesso tempo, aziona un meccanismo di resistenza passivo, di elusione dello stress, permettendo di tollerare la presenza di sale, in quanto ne impedisce l’entrata all’interno del tallo lichenico.
Da un punto di vista pratico la conservazione della specie dovrebbe essere attuata garantendo le condizioni ideali a tutti gli stadi di crescita (ad esempio proteggere i propaguli dalla fotoinibizione). In caso di necessità di intervento valutare su scala locale la dinamica di popolazione e utilizzare questo dato per selezionare le aree e gli arbusti sui quali effettuare gli interventi.Light regime, water availability and high salt concentrations are generally the main ecological factors modified by habitat fragmentation that could be detrimental to the survival and establishment of poikilohydric organisms such as lichens, causing rapid dehydration, ionic imbalances and the inhibition of photosynthesis. In the Mediterranean basin, coastal juniper habitats, priority habitat for nature conservation (Natura 2000 habitat code 2250), are known to host numerous epiphytic lichens, that living near the seashore need a morphological and chemical organization to adapt or acclimate to extremely variable disturbances. Among them, the macrolichen Seirophora villosa, which consists in a fruticose habitus characterized by the presence of compressed canaliculated laciniae covered by thin hairiness and the absence of secondary surface metabolites. Recently studies, has demonstrated the dependence of S. villosa on undisturbed Juniperus stands suggesting a significant effect of disturbance on the presence of this lichen species. Moreover, it has been demonstrated that S. villosa is only occupying a small part of its colonizable niche because of a very limited propagation ability.
Since the presence and abundance of S.villosa are positive indicators of the conservation status of coastal nurseries, our study aimed to evaluate the effects of the main ecological variables on the eco-physiology of this species. Our first aim was to investigate whether the habitat structure affects the functional diversity and species richness of lichen communities along a coastal dune system and how affects the presence of S. villosa. Our second aim was to investigate how light regime and water availability affect individual specimens of S. villosa, by studying the relationship between photosynthetic activity and water content to thallus area in different sized. Furthermore, we investigated the role of the thin hairiness on thallus surface characterizing S. villosa to withstand the effects of seawater by continuous exposure to marine aerosol.
Our results showed that epiphytic lichens richness and habitat width used as proxy of habitat integrity. Juniperus stands with higher individuals and cover continuity, probably ensuring a major stability of microclimatic factors, supported richer and functionally more differentiated epiphytic lichen communities. In contrast, the presence of S. villosa resulted not directly related to the habitat structure, suggesting a major role of dispersal and establishment capability therefore suggesting a management tailored at the tree-level aimed to the conservation of mature (apotheciate) specimens. However, ongoing research indicate a possible role of microhabitat structure on the abundance of this species.
The experiments carried out showed that the size of the thalli influence the water retention capacity of S.villosa species, and consequently influence responses to strong exposure to light. Our outcomes showed that S. villosa are susceptible to sudden increases in light exposure, especially in the case of small specimens, which after photoinhibition exhibited a reduced ability to recover. Moreover, our work evidenced for the first time the relevance of hair as a strategic morphological trait in lichens to face extreme environments. Our results suggest that hair could offer a passive, but selective, water control. Furthermore, hair could repel the salt dissolved in water, by activating a passive resistance mechanism, a real avoidance of stress, which by not allowing salt to enter, allows the thallus to tolerate the presence of salt.
In conclusion, from a conservation point it would be necessary to preserve all the growth stages of the population, providing a suitable habitat for the larger thalli that have the role of propagate the species and for the smaller ones giving them the opportunity to colonize and establish in fragment habitat without being photohinbited
Opere di regimentazione delle acque in età arcaica. Roma, Grecia e Magna Grecia, Etruria e mondo italico, Roma
No full textIl volume raccoglie una serie di contributi sui sistemi di regimentazione delle acque in età arcaica, in Grecia, Magna Grecia, Sicilia, mondo Italico e Rom
FIGURE 1 in Revision of the Parmelia saxatilis group in Italy based on morphological, chemical, and molecular data
No full textFIGURE 1. Bayesian consensus tree based on ITS region. Posterior Probabilities and Bootstrap values are indicated near the nodes when> 0.5 and 50% respectively. A clade consists of the P. sulcate group. Clade B represent the P. saxatilis group. Samples in bold are the original materials of this study, the number in parenthesis corresponds to the collection id shown in Table 1. Previously published sequences from GenBank are reported with ID species / GenBank (Table 3).Published as part of <i>Castellani, Maria Beatrice, Bianchi, Elisabetta, Coppi, Andrea, Nascimbene, Juri & Benesperi, Renato, 2021, Revision of the Parmelia saxatilis group in Italy based on morphological, chemical, and molecular data, pp. 28-40 in Phytotaxa 512 (1)</i> on page 33, DOI: 10.11646/phytotaxa.512.1.2, <a href="http://zenodo.org/record/10273302">http://zenodo.org/record/10273302</a>
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
