1,721,032 research outputs found
Spatiotemporal variation in the pollination systems of a supergeneralist plant: is Angelica sylvestris (Apiaceae) locally adapted to its most effective pollinators?
Get PDFBackground and Aims: In terms of pollination systems, umbellifers (plants of the carrot family, Apiaceae) are regarded as generalists, since their (usually dichogamous) flowers are visited by a wide range of insects representing several taxonomic orders. However, recent analyses of insect effectiveness revealed that these plants may be pollinated effectively by a narrow assemblage of insect visitors. Of particular interest was whether populations of an umbellifer species varied in pollinator assemblages and whether this could lead to local specialization of the pollination system. We also explored whether variation in pollinator assemblages was associated with variation in floral traits, and whether this variation influences reproductive output. Methods: The focus was on Angelica sylvestris, a common European species visited by a taxonomically diverse insect assemblage. In three populations, located along an ~700-km transect, over three growth seasons insect visitors were identified, their effectiveness was assessed by surveying pollen loads present on the insect body, insect activity on umbels, nectar and scent composition was studied, and transplantation experiments were performed. Key Results: The populations investigated in this study differed in their nectar and scent profiles and, despite the similar taxonomic composition of insect visitor assemblages, were effectively pollinated by disparate pollinator morphogroups, i.e. flies and beetles. Although this suggested local adaptations to the most effective pollinators, analyses of body pollen loads and behaviour on umbels demonstrated functional equivalency of the visitor morphogroups, which is probably related to the fact that A. sylvestris bears few ovules per flower. The transplantation experiments confirmed that reproductive success was not related to the source of experimental plants and that the insects do not exhibit preferences towards local genotypes. Conclusions: Angelica sylvestris is morphologically well adapted to ecological generalization, and there is little evidence that the surveyed populations represent distinct pollination ecotypes. Most likely, the observed variation in floral characters can be interpreted as 'adaptive wandering'. Specialization in this family seems possible only under very special circumstances, for example when the pollinator community comprises insect visitor groups that clearly differ in their pollination capacity (e.g. due to differences in their functional morphology) and/or have different perceptional biases (e.g. for colour or scent). However, the barrier to the evolution of morphological adaptations resulting in the fine-tuning of the flower towards particular pollinator types may arise from the architectural constraints on the floral bauplan that make umbellifers so uniform in their floral displays and so successful in attracting large numbers of pollinators
Ewolucja kwiatu w rodzaju Fritillaria L. (Liliaceae) w odpowiedzi na zmianę głównego zapylacza
No full textW jaki sposób wielkość populacji i dostępność zapylaczy moduluje system rozrodu i strukturę genetyczną roślin? Przypadek wielosiłu błękitnego (Polemonium caeruleum, Polemoniaceae), limitowanego pyłkiem gatunku z "Polskiej Czerwonej Księgi Roślin"
No full textLink archiwalny https://depotuw.ceon.pl/handle/item/462
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
Application of regression and classification models of rocks by artificial neural networks methods
No full textPrzeprowadzono modelowanie krzywej czasu interwałowego DT przy pomocy metod sztucznej inteligencji, na podstawie innych krzywych pomiarowych z tego samego otworu oraz wyników profilowań geofizyki otworowej z dwóch innych otworów. Wnioski i informacje zdobyte w modelowaniu wykonanym na danych z otworów o znanym DT zostały wykorzystane do konstrukcji modelu dla otworu, w którym DT nie zostało pomierzone. Optymalną krzywą DT otrzymano upraszczając model poprzez zmniejszenie liczby zmiennych wejściowych. Jako kryterium wyboru najlepszej krzywej uznano korelację z rzeczywistymi krzywymi pomierzonymi w innych otworach oraz wartością czasu interwałowego DPEQ obliczoną w aplikacji interpretacyjnej. Dokonano próby podziału utworów w otworach na grupy przy pomocy metod klasyfikacyjnych Kohonena. Poprzez zmianę liczby skupień, do których sieć ma przyporządkowywać przypadki wybrano optymalny model. Grupowanie przypadków sieciami Kohonena odpowiada w przybliżeniu podziałowi litostratygraficznemu w otworach.Artificial neural network methods was used to model curve of interval times DT in boreholes, based on data from other geophysical curves and other two boreholes in witch DT was measured. The best DT curve was gained simplifying model by reducing number of variables. To choose the best correlation all modeled curves was compared to measured DT and interval time DPEQ, obtained from application estimating geophysical curves, in boreholes in witch DT wasn’t measured. Author also classified soil layers using Kohonen’s self-organizing maps. Optimal model was chosen by changing number of clusters in which artificial network gather samples. The result is comparable to lithostratigraphic divisions received with data.praca magistersk
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
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