1,720,964 research outputs found
Different points of view in a changing world: The tobacco tree flowers through the eyes of its pollinators in native and non-native ranges
No full textDifferent pollinators show distinct visual and cognitive abilities that can influence floral colour evolution. Nicotiana glauca is a South American hummingbird-pollinated plant that has become a significant invasive of semi-arid parts of the world, where it is visited by local animals like sunbirds in South Africa or diurnal hawkmoths in Spain. We measured corolla reflectance spectra from native and non-native populations encompassing the different pollination contexts. Flower colour loci were represented in the visual space of tetrachromatic birds and trichromatic hawkmoths. Variation in corolla reflectance spectra was revealed, both across pollination contexts and among populations. From the pollinators' point of view (hummingbirds, sunbirds and hawkmoths), flowers from native populations were, in general, significantly discriminated from those of the non-native populations, which mostly were not discriminated as different from each other. We discuss our findings under the hypothesis of pollinator-mediated colour selection and alternative evolutionary processes that may occur during invasions.Fil: More, Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Costa, Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Paiaro, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Drewniak, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Coetzee, Anina. University of Cape Town; Sudáfrica34th Annual Meeting of the Scandinavian Association for Pollination EcologyNorthamptonReino UnidoScandinavian Association for Pollinatio
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
The effect of supplementary nectar feeders on bird-plant mutualisms in the Cape Fynbos, South Africa
Get PDFAcross the world, people feed birds to interact with nature. A variety of feeder types have been developed over the years to target a broad bird community. Attracting nectarivorous birds to gardens using supplementary nectar feeders is a popular human activity across the globe, but few studies have explored its effects on birds and the plants they pollinate. Nectar feeders may have positive effects, facilitating the urban adaptation of nectarivorous birds, and supplementing their diets when floral resources are scarce. However, supplementary feeders may also lure birds away from indigenous vegetation, affecting the rate of visits to bird-pollinated plants, with consequences for seed set. This study is the first to investigate the effect of nectar feeders on an African plantpollinator mutualism. Given that many plant species in the fynbos biome are bird pollinated, this study was conducted in residential gardens and natural vegetation along the urban edge of the Cape Peninsula, South Africa. I carried out a feeding experiment with a matched paired design to answer two main questions: (1) Do nectar feeders affect bird abundance and distribution ranges? If so, (2) do these affect their visitation rates to bird-pollinated plants? I conducted bird surveys to compare relative bird abundance and local distribution patterns for three feeding guilds (i.e., nectar-specialists, nectar-opportunists and non-nectarivores) between feeder and control treatments (Chapter 2). I then tested whether the presence of nectar feeders in gardens affected sunbird visitation rates to two bird-pollinated Erica species (Erica plukenetii subsp. plukenetii and Erica abietina subsp. atrorosea) in the neighbouring vegetation compared to control sites (Chapter 3). In chapter 2, I found that nectar feeders attracted higher densities of avian nectarivores (but not non-nectarivores) to gardens relative to natural vegetation, and decreased their densities in the neighbouring fynbos, even when floral abundance in the neighbouring vegetation was high. In chapter 3, I found that the consequent changes to sunbird distribution patterns (the main pollinators of ericas) seemed to have no influence on visitation rates to E. abietina, but decreased visitation to E. plukenetii flowers within 300 m of gardens with feeders. Thus, nectar feeders may have positive effects for birds themselves by reducing their urban sensitivity but may also have negative effects on the surrounding fynbos ecosystem. Given that nectar feeders appear to compete with the flowers of E. plukenetii, and perhaps those of other birdpollinated species, supplementary feeding may inadvertently threaten bird-plant pollination networks. This issue is particularly concerning in biomes such as the Cape Floristic Region where many bird-pollinated plants occur near urban edges
Nectar distribution and nectarivorous bird foraging behaviour at different spatial scales
Get PDFThesis (PhD)--Stellenbosch University, 2016.ENGLISH ABSTRACT: While foraging strategies of animals may be shaped by the distribution of their food resources, these strategies in turn also affect the ecology and evolution of their resources. In this regard, African systems, of all the different bird-pollination systems worldwide, have been least studied. I investigated the relationships between these aspects at population, community and landscape levels in the bird-pollination systems of the Cape Floristic Region. This biodiversity hotspot in the southwest of South Africa contains an unusually high number of bird-pollinated plant species relative to the number of pollinating bird species.
Chapter 2 describes how I experimentally tested which nectar resource traits affect sunbird foraging behaviour at the small scale within populations. Sunbirds’ behaviour was largely determined by visual signals and distances between nectar resources. The birds showed flower colour preferences, but no flower constancy (selective foraging only on one flower type).
The foraging behaviour of pollinators seems to influence plant community assembly. With the use of null models, I show in Chapter 3 that communities of Proteaceae, a diverse and dominant plant family in the Cape Floristic Region, are structured both by competition for and facilitation of pollination. This was deduced from the non-random structure of the plant communities with respect to pollination syndromes and style lengths, which are proxies of the degree of pollinator sharing and of interspecific pollen transfer.
While species traits were important driving forces of community assembly in natural habitat, I show in Chapter 4 that species and habitat traits may also be important factors structuring bird communities in novel environments such as human settlements. Through a questionnaire, I determined how well different species of nectarivorous birds are adjusting to urban environments and which traits facilitate and prevent this adjustment. Nectar-generalist birds were successful exploiters of urban resources and were most abundant in gardens with large vegetated areas, bird baths and feeders. Nectar-specialist birds were less successful at adjusting, due to their high dependence on nectar. The presence of sugar water feeders and the number of indigenous bird-pollinated plants in gardens best predicted the communities of nectar-specialist birds. All nectarivorous birds were negatively affected by dispersal barriers.
Lastly, in Chapter 5, I use biome-wide atlas databases for birds and proteas to show how nectar distribution affects bird abundances at a landscape scale. The non-significantly different flowering phenology patterns throughout the biome suggest that nectarivorous birds would not need to migrate seasonally. Instead, birds may be sustained within mountain ranges all year round by the complementary flowering of species of different genera. Low floral abundances in the dry months of the year may still produce resource bottlenecks and this may encourage birds to forage in areas of human settlement.
Though we have gained insight into some of the relationships between African nectarivorous birds and their nectar resource distributions in space and time, there is still much to learn. There is also an urgent need to understand the effects of land-use change on the long-term persistence of nectar-feeding birds of the Cape Floristic Region.AFRIKAANSE OPSOMMING: Die voedingsstrategieë van diere kan gefatsoeneer word deur die verspreiding van hul voedselbronne, maar terselfdertyd kan hierdie strategieë die ekologie en evolusie van hul voedselbronne affekteer. In hierdie opsig is Afrika sisteme, van al die verskillende voëlbestuiwingssisteme wêreldwyd, die minste bestudeer. Ek het die verhoudings tussen hierdie aspekte in die voëlbestuiwingsisteme van die Kaapse Blommeryk op populasie-, gemeenskaps- en landskapsvlak ondersoek. Hierdie biodiversiteit-brandpunt in die suid-weste van Suid-Afrika huisves ‘n ongewone groot aantal voëlbestuifde plantspesies teenoor die aantal voëlbestuiwerspesies.
Hoofstuk 2 beskryf hoe ek eksperimenteel getoets het watter nektarbroneienskappe die voedingsgedrag van suikerbekkies op klein skaal binne populasies affekteer. Suikerbekkies se gedrag is grootendeels bepaal deur visuele seine en die afstande tussen nektarbronne. Die voëls het blomkleurvoorkeure getoon, maar nie blomkonstantheid (selektiewe voeding op een blomtipe) nie.
Die voedingsgedrag van bestuiwers blyk plantgemeenskapsamestelling te affekteer. Met die gebruik van nulmodelle, wys ek in Hoofstuk 3 dat gemeenskappe van Proteaceae, ‘n dominante plantfamilie in die Kaapse Blommeryk, deur beide kompetisie vir en fasilitering van bestuiwing gestruktureer word. Dit is afgelei uit die nie-ewekansige struktuur van plantgemeenskappe met betrekking tot bestuiwingsindrome en styllengtes, wat ‘n maatstaf is van interspesifieke stuifmeeloordrag en die mate waartoe plante bestuiwers deel.
Terwyl spesies-eienskappe belangrike dryfkragte was in gemeenskapsamestelling in natuurlike habitat, wys ek in Hoofstuk 4 dat spesie- en habitateienskappe ook belangrike faktore kan wees in die strukturering van voëlgemeenskappe in nuwe omgewings soos menslike nedersettings. Ek het deur ‘n vraelys bepaal hoe goed nektarvretende voëls in stedelike omgewings aanpas en watter eienskappe hierdie aanpassing fasiliteer of verhoed. Nie-spesialis nektarvretende voëls was suksesvolle uitbuiters van stedelike bronne en was die volopste in tuine met groot beplante areas, voëlbaddens en -voerders. Nektarspesialis voëls het minder suksevol aangepas, weens hul hoë afhanklikheid van nektar. Die teenwoordigheid van suikerwatervoerders en die aantal inheemse voëlbestuifde plante in tuine was die belangrikste bepalers van nektarspesialis voëlgemeenskappe. Alle nektarvretende voëls was negatief geaffekteer deur verspreidingshindernisse.
Laastens gebruik ek in Hoofstuk 5 bioomwye atlasdatabasisse van voëls en proteas om te wys hoe nektarverspreiding voëlgetalle op die landskapsvlak affekteer. Die nie-beduidende verskille in blombloeiingspatrone regdeur die bioom suggereer dat nektarvretende voëls nie seisoenaal hoef te migreer nie. Voëls kan regdeur die jaar binne bergreekse onderhou word deur komplimentêre bloeipatrone van spesies van verskillende genera. Die lae getal blomme in die droeë maande van die jaar kan steeds voedselbronbottelnekke veroorsaak en dit mag dalk voëls aanmoedig om in menslike nedersettings voedsel te soek.
Alhoewel ons insig oor die sommige van die verhoudings tussen Afrika nektarvretende voëls en die verspreiding van hul nektarbronne in tyd en ruimte gegroei het, is daar steeds baie om te leer. Daar is ook ‘n dringende behoefte om die effek van veranderings in landgebruik op die langtermyn-voortbestaan van nektarvretende voëls van die Kaapse Blommeryk te verstaan.Doctora
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
- …
