1,721,018 research outputs found
Biosystematic studies on the mountain plant Gentiana lutea L. reveal variability in reproductive traits among subspecies
No full textBackground: Taxonomic analysis provides a basic understanding for taxon identification and contributes to preliminary information for several branches of applied biology, while studies on reproductive strategies and plant fitness are essential to interpret population status and dynamics. Aims: We tested the reliability of diagnostic characters for identification and to characterise sexual resource allocation, the breeding system and seed predation among subspecies of Gentiana lutea. Methods: We analysed morphological characters in 70 herbarium specimens. In five natural populations we counted pollen and ovule numbers, assessed reproductive output after pollination treatments and evaluated pre-dispersal predation. Results: Taxonomic traits previously indicated as diagnostic were not sufficient to discriminate among subspecies. The pollen number and pollen:ovule (P:O) ratio varied strongly among subspecies; self-pollinated flowers produced a significantly lower number of seeds than open-pollinated flowers. Retention of empty fruits and high levels of pre-dispersal seed predation were observed in every case. Conclusions: The variation of P:O ratios among subspecies suggests different efficiency in pollen transfer. The species is self-compatible, nevertheless all subspecies require pollen vectors to enhance cross pollination and viable seed production. Fruit retention may have evolved as a strategy to reduce predation, ensuring higher plant fitness
The effect of pollination mode on seed performance of Gentiana lutea: A laboratory evaluation of seed germinability
No full textGentiana lutea L. (yellow gentian, Gentianaceae) is a protected orophyte of central and southern Europe, mainly threatened by the uncontrolled collection of its rhizome, used in traditional medicine and for liquor production. The species is self-compatible, but outcrossing mediated by pollinators is needed to obtain a viable progeny. In this study, we considered five natural populations belonging to the four subspecies of G. lutea. We performed controlled pollinations in the field (self- versus cross-pollination) followed by seed germination tests in laboratory conditions, adding a solution of gibberellic acid, in order to evaluate the seed performance. A cumulative index of inbreeding depression was calculated considering maternal reproductive output as well as seed performance traits. Seed weight and seed germination performance was similar between seeds resulting from naturally pollinated and pollen-augmented flowers and higher compared to selfed flowers, highlighting a disadvantage of selfing and the importance of cross-pollen transfer in natural conditions. However, in the small and isolated population of G. lutea subsp. symphyandra on Mt Grande we found a general reduction in seed germination rate, likely due to increased selfing or mating among close relatives as a consequence of a severe bottleneck. We discuss our results with regards to implications for conservation practices
Lack of partner preference system for incest avoidance in the bumble bee Bombus terrestris
No full textInbreeding is caused by the mating of closely related individuals and
produces a decrease in the offspring fitness and deleterious consequences for
adults. In haplodiploid social Hymenoptera inbreeding has a further negative effect
because of their particular mechanism of sex determination (sl-CSD), that causes
the emergence, in half of the founded colonies, of unviable or sterile diploid males.
When these males are able to develop until adult stage, as in bumble bees, they
represent a huge cost for the colony. With respect to these high inbreeding
consequences, a selection for mechanisms of inbreeding avoidance would be
expected in bumble bees. Social recognition is one of the most common and
efficient system to avoid inbred mating in social insect, but it is poorly studied in
bumble bees. In this study we investigated the mating choice between siblings or
non-siblings in queens and males of Bombus terrestris reared in laboratory. To
investigate the role of mating behaviour in mating choice, the tests were performed
both in cage and in tunnel. As opposed to what would be expected, we found that
B. terrestris males and gynes do not show a mating preference for non-siblings
compared to siblings (49.3% in non-siblings and 50.7% in siblings) and the mating
latency was even shorter for sibling matings than for non-siblings ones
Temporal activity patterns in a flower visitor community of Dictamnus albus in relation to some biotic and abiotic factors
No full textSeveral biotic and abiotic factors affect the seasonal and daily activities of flower-visiting insects, which, ultimately, influence the composition and abundance of a pollinator community and the extent of their pollination service. The aim of this four-year study was to assess the effect of some abiotic and biotic factors on the abundance and activity pattern of flower-visiting insects throughout the blooming of a locally rare plant species, Dictamnus albus L. (Rutaceae). We found a large inter-annual variation in the abundance and activity of flower visitors, with up to a six-fold variation in the total number of individual insects observed. Moreover, a similar fluctuation among years was also highlighted by biodiversity indices and by the changes in the relative frequency of each flower-visiting taxon. Annual, seasonal and daily variations were explained by a certain level of “response diversity” between flower-visiting taxa in relation to different environmental conditions during D. albus blooming. The foraging activity was related to ambient temperature in the tribe of Halictini and to relative humidity in four flower-visiting taxa (positive relation in the tribe Anthophorini; negative relation in the taxa Megachilini, Halictini and Syrphidae). The climate conditions during the winter might have also affected the phenology and the abundance of flower-visiting taxa with a large number of insects observed in warmer years. Among the biotic factors, flower availability did not affect the abundance of insects observed in the patch. Moreover, we did not find any significant negative associations (e.g. possible competition) in the co-occurrence of different flower visiting taxa, instead we found six significant positive associations probably related to similar preferences towards specific environmental conditions. In conclusion, our results show that the flower visitor community of D. albus is quite variable among years, seasons and daily hours, but the relative high visitor diversity and the different patterns of activity related to different environmental responses might guarantee a stable pollination service of this plant species in years with extreme environmental conditions
Integrated conservation of bee pollinators of a rare plant in a protected area near Bologna, Italy
Full text linkAn integrated approach was proposed for the conservation of the bee pollinators of the locally rare plant dittany Dictamnus albus. Based on previous studies that revealed the most efficient pollinators, we performed three related actions to improve their presence in the area: (i) we provided artificial nests for bumblebees and solitary bees; (ii) we added bee plants to support local populations of pollinators throughout their life cycle, and (iii) we reared and released bumblebee colonies from wild queens collected in the area. Artificial nests were occupied at high rates by cavity nesting species such as mason bees, leafcutter bees and carpenter bees, while we did not observe any ground nesting bees. Artificial nests for bumblebees did not attract any wild queens. The bee plants established at different rates: transplanted adult individuals survived better than seeds directly sown at the site. In three consecutive years we reared and released several colonies of buff-tailed bumblebees, which survived through the flowering season but only one developed new gynes
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
CONSERVAZIONE INTEGRATA DI UNA PIANTA RARA E MINACCIATA E DELLA COMUNITA' DEI SUOI IMPOLLINATORI SELVATICI: PROGETTO LIFE+ PP-ICON (LIFE09/NAT/IT/000212)
No full textIl progetto PP-ICON (Plant Pollinator Integrated CONservation approach: a demonstrative
proposal) è un progetto LIFE+ Biodiversità della durata di 4 anni incentrato sulla conservazione
integrata di una pianta localmente rara, Dictamnus albus L., e sulla comunità dei suoi impollinatori.
Il sito di intervento si trova all'interno di un’area protetta della provincia di Bologna (Parco
Regionale dei Gessi Bolognesi e Calanchi dell'Abbadessa), che è anche un sito di interesse
comunitario (SIC-ZPS IT4050001 Rete Natura2000).
Le azioni si concentrano in quattro ambiti principali: gestione dell'habitat, salvaguardia degli
impollinatori, sensibilizzazione degli stakeholders e divulgazione. Gli interventi sull’habitat sono
consistiti nella creazione di schiarite boschive, al fine di ristabilire le migliori condizioni ambientali
per la persistenza della pianta, che soffre per la chiusura del bosco. Sono stati individuati gli
impollinatori effettivi del dittamo, al fine di fornire loro siti di nidificazione idonei, e alcune specie
di bombi sono state allevate artificialmente e reintrodotte nella zona. Il sostentamento degli
impollinatori è stato anche favorito dall'incremento delle fonti mellifere, ossia della flora spontanea
necessaria a fornire loro nettare e polline. A tale scopo sono state scelte 16 specie già presenti
nell'area e con una fioritura scalare, per garantire la presenza di fonti alimentari per tutto il periodo
di sviluppo degli insetti. Il successo delle azioni di conservazione viene valutato attraverso il
monitoraggio periodico della fitness della pianta e della diversità degli impollinatori.
Dopo tre anni dall'inizio del progetto la gestione del bosco ha dato esito positivo, con un incremento
della luce incidente nelle due aree di taglio di rispettivamente 5 e 2 volte rispetto alle due aree di
controllo, e un aumento di 6 volte del numero di piante fiorite. L'introduzione di 6 gruppi di nidi
artificiali ha avuto successo per diverse specie di api solitarie (es. varie Megachilidae e Xylocopa
sp.), mentre i 10 nidi per bombi non sono stati colonizzati. Tuttavia, in tre anni, 17 colonie di
Bombus terrestris sono state allevate con successo in laboratorio e reintrodotte nella zona. Le piante
nettarifere trapiantate vengono assiduamente visitate dagli impollinatori selvatici e, anche se i dati
del monitoraggio indicano ancora una generale scarsità di fauna impollinatrice, vi è una relazione
positiva tra abbondanza degli impollinatori e diversità delle specie di fiori; nell’anno successivo
all’introduzione delle nettarifere infatti l’indice di Shannon è aumentato in media di 0,25 punti ogni
mese rispetto all’anno precedente.
Gli eventi di divulgazione, che si concentrano sul rapporto tra piante e impollinatori e sulle strategie
per la loro conservazione, hanno attirato un numero sempre crescente di persone negli anni del
progetto, contribuendo a sensibilizzare l'opinione pubblica sull'importante tema della conservazione
della biodiversità
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
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