257 research outputs found
EcologÃa alimentaria del Picaflor Cometa <i>Sappho sparganura</i> en la provincia de Córdoba, Argentina
Se estudió la alimentación invernal y estival del Picaflor Cometa (<i>Sappho sparganura</i>) en tres localidades de las sierras de Córdoba. Este es el único picaflor que permanece en invierno en la provincia y a lo largo del año realiza desplazamientos altitudinales siguiendo la floración de diferentes especies. Aunque utiliza en forma indistinta plantas nativas e introducidas, incluso no especializadas para la ornitofilia, interactúa fuertemente con cinco especies indÃgenas: todas ellas son ornitófilas y <i>S. sparganura</i> serÃa un elemento importante para su reproducción. No obstante ello, en dos de los sitios una planta exótica (<i>Chaenomeles lagenaria</i>) fue la que posibilitó la permanencia del picaflor en los inviernos más frÃos.Summer and winter foraging of the Red-tailed Comet (<i>Sappho sparganura</i>) was studied in three sites in the Córdoba mountain range. This is the only hummingbird species overwintering in the province. Along the entire year it does altitudinal movements looking for different blooming plants. Although the Red-tailed Comet does not discriminate between native or introduced plants, feeding even on non-ornithophilous ones, it strongly interacts with five indigenous species. All of them are ornithophilous species and the hummingbirdÃs visits would be important for reproduction of these plants. However, in two of the sites an exotic species (<i>Chaenomeles lagenaria</i>) was the most important resource allowing overwintering of the Red-tailed Comet in colder years
Primeros registros de <i>Cyanocompsa cyanea</i> en la provincia de Buenos Aires y notas sobre su presencia en Entre RÃos
The Ultramarine Grosbeak (<i>Cyanocompsa cyanea</i>) is reported for the first time for Buenos Aires Province. Data on the general distribution of the species in Argentina (particulary Entre RÃos) is given
Asociación de dos especies de picaflores con árboles del género <i>Eucalyptus (Myrtaceae</i>) en la provincia de Buenos Aires
Association two species of hummingbirds with trees of the genus <i>Eucalyptus</i> (Myrtaceae) in the province of Buenos Aires. The importance of <i>Eucalyptus</i> trees, in particular the <i>E. globulus</i>, in the diet of some species of hummingbirds, specially during the winter, has been reported. Field observations carried out in Villa Gesell (on <i>Leucochloris albicollis</i>), Pereyra Iraola and Ezeiza (on <i> Hylocharis chrysura</i> ), indicate that this association is also present in the province of Buenos Aires. Our observations during late autumn lend support to the belief that both hummingbird species are permanent residents in Buenos Aires province. However, this has not been clearly stated in the bibliography. On the contrary, there are opposed opinions regarding whether the <i> H. chrysura</i> is or is not a permanent resident, while available data on <i> L. albicollis</i> are insufficient to shed a definite light on the matter
Non-Asteraceae plants in the diet of the Hooded Siskin (<i> Carduelis magellanica</i> )
Según los antecedentes Carduelis magellanica habita áreas semiabiertas o cultivadas, con árboles esparcidos, y se alimenta básicamente de semillas de Asteráceas. En el presente trabajo se comunica que hay varias plantas (la mayorÃa exóticas) de otras familias botánicas que son utilizadas por este carduelino en la provincia de Buenos Aires, Argentina. Una de el as (Fraxinus pennsylvanica, Oleáceas) está muy difundida como árbol de calle y su prolongada oferta de frutos (de marzo a diciembre) explicarÃa la presencia frecuente del Cabecitanegra Común en la ciudad de Buenos Aires.Literature reports indicate that Carduelis magellanica inhabits semiopen or cultivated areas with scattered trees, feeding mostiy on Asteraceae seeds. In this paper we provide a list of 10 non-Asteraceae plants consumed by this cardueline finch in the province of Buenos Aires, Argentina. The extended fruit availability (from March to December) of one of them (Fraxinus pennsylvanica, Oleaceae), a widespread exotic street tree, probably explains why the Hooded Siskin is fairly common in Buenos Aires city
Genetic engineering applications in animal breeding
This paper discusses the use of genetic engineering applications in
animal breeding, including a description of the methods, their
potential and current uses and ethical issues. Genetic engineering is
the name of a group of techniques used to identify, replicate, modify
and transfer the genetic material of cells, tissues or complete
organisms. Important applications of genetic engineering in animal
breeding are: 1) Marker-assisted selection (MAS). The objective of this
technology is to increase disease resistance, productivity and product
quality in economically important animals by adding information of DNA
markers to phenotypes and genealogies for selection decisions. 2)
Transgenesis, the direct transfer of specific genes/alleles between
individuals, species, or even Kingdoms, in order to change their
phenotypic expression in the recipients. Compared to the 'traditional'
improvement techniques based on phenotypic information only, these
gene-by-gene techniques allow theoretically a more complete management
of animal genomes for animal breeding. In spite of high expectations
and new technical developments, its actual efficiency is not always
high, as they require a thorough knowledge of functional genomics, and
pose additional technical, economical and ethical problems. The
possible role for cloning adult animals in breeding is also discussed
Visitantes florales diurnos del girasol (Helianthus annuus L., Asterales: Asteraceae) en la Argentina
El girasol (Helianthus annuus L.) es un importante cultivo oleaginoso en la Argentina. Durante tres campañas agrÃcolas, se determinaron la diversidad y la abundancia del elenco de los visitantes florales diurnos de capÃtulos de girasol, en ocho sitios que cubren gran parte del área cultivada en Argentina. Setenta y seis morfo-especies de visitantes florales, pertenecientes a ocho órdenes, fueron capturados sobre capÃtulos de este cultivo. El principal orden fue Hymenoptera, con 37 especies o morfoespecies, de las cuales 32 fueron abejas (Apoidea). Las familias de abejas más representadas fueron Apidae (13), Megachilidae (11) y Halictidae (7). La abeja doméstica (Apis mellifera L.) realizó el 93% de las visitas. La composición del elenco de visitantes no mostró un patrón de variación identificable a lo largo del dÃa, ni con respecto a la distancia al borde del cultivo, pero varió entre sitios de muestreo. Se concluye que la abeja doméstica es el principal polinizador del girasol en la Argentina, aunque varias especies nativas de abejas (Melissodes tintinnans (Holmberg), M. rufithorax Brèthes, Melissoptila tandilensis Holmberg, y Megachile spp.) podrÃan ser consideradas como potenciales polinizadores del cultivo.Sunflower (Helianthus annuus L.) is an important oilseed crop in Argentina. During three agricultural years, the diversity and abundance of diurnal floral visitors of sunflower heads were determined in eight sites spanning much of this crop’s cultivation area in Argentina. Seventysix morpho-species of floral visitors, belonging to eight orders, were captured on sunflower. The principal order was Hymenoptera, with 37 species or morpho-species, of which 32 were bees (Apoidea). The most represented bee families were Apidae (13), Megachilidae (11) and Halictidae (7). The domestic bee (Apis mellifera L.) accounted for 93% of the visits. Floral visitor composition did not show an identifiable variation pattern either throughout the day or with respect to the distance to the edge of the crop, but varied among sites. It is concluded that the domestic bee is the main sunflower pollinator in Argentina, although several native bee species (Melissodes tintinnans (Holmberg), M. rufithorax Brèthes, Melissoptila tandilensis Holmberg, and Megachile spp.) could be considered as potential crop pollinators.Fil: Torretta, Juan Pablo. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica AgrÃcola; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Medan, Diego. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica AgrÃcola; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Roig Alsina, Arturo Hernan. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Montaldo, Norberto H.. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica AgrÃcola; Argentin
Use of molecular markers and major genes in the genetic improvement of livestock
Recent developments in molecular biology and statistics have opened the
possibility of identifying and using genomic variation and major genes
for the genetic improvement of livestock. Information concerning the
basis of these techniques and their applications to the genetic
improvement of animals is reviewed. Main marker molecular marker
systems in animals (RFPL and microsatellites), genome maps, methods for
detecting marker major gene linkages and use of marker assisted
selection, genetic fingerprinting and mixture models based on
segregation analysis are analyzed. The characteristics where the
application of marker assisted selection can be more effective are
those that are expressed late in the life of the animal, or controlled
by a few pairs of genes. The first example correspond to the longevity
and carcass characteristics in meat producing animals, the second, to
the resistance to certain diseases or defects of simple inheritance.
The detection of major genes using mixture models with segregation
analysis can direct the work of identification of DNA marker genotypes
towards populations and characteristics with greater probability of
detecting a major gene using molecular markers. The present trend
indicates that molecular, pedigree and phenotypic information will be
integrated in the future through mixture models of segregation analysis
that might contain major gene effects through the markers, polygenic
inheritance and uses powerful and flexible methods of estimation such
as Gibbs Sampling
Gli effetti dell’introduzione della nuova mappa di pericolosità sulla valutazione del rischio sismico in Italia.
L’introduzione di una versione aggiornata della mappa di pericolosità sismica, definita per diversi periodi di ritorno e per svariati valori di ordinate spettrali, porta inevitabilmente a dei cambiamenti sul livello di rischio sismico del costruito italiano. Poiché la relazione tra domanda e capacità non è lineare per tutto il range di periodi
di vibrazione strutturale, è necessario valutare il cambiamento del livello di rischio sismico calcolando esplicitamente la vulnerabilità sismica di strutture esistenti con diversi periodi di vibrazione, per diversi stati limite e considerando sia la nuova che la precedente definizione di pericolosità . Nel presente lavoro è stato
eseguito un primo studio degli effetti che l’introduzione di mappe aggiornate della pericolosità sismica potrebbe avere sulla valutazione dei livelli di rischio sismico nel territorio italiano. Le caratteristiche generali del costruito sono state ricavate dai dati del 14° Censimento Generale della Popolazione e delle Abitazioni (ISTAT
2001), mentre una procedura probabilistica di valutazione sismica per edifici esistenti a scala urbana è stata impiegata per stimare la capacità . Sono stati considerati tutti i tre stati limite prescritti dall’Ordinanza
(danno lieve, danno severo, collasso) in corrispondenza dei rispettivi valori di domanda, così come il cambiamento delle forme spettrali in funzione della localizzazione e del periodo di ritorno. I risultati dimostrano che la nuova mappa di pericolosità sismica porta a dei livelli di rischio sismico più realistici e meno allarmanti,
rendendo leggermente meno gravoso, anche se non privo di problematiche, il panorama attuale di rischio in Italia
Sistema reproductivo y polinización de especies leñosas en una selva subtropical invadida por plantas exóticas
675-689En la selva ribereña de Punta Lara (provincia de Buenos Aires, Argentina) conviven siete especies leñosas dispersadas por aves, de las cuales cinco son nativas (Ocotea acutifolia, Allophylus edulis, Myrsine laetevirens, Blepharocalyx salicifolius y Citharexylum montevidense) y dos son exóticas invasoras (Rubus ulmifolius y Ligustrum lucidum). Si bien allà se ha estudiado la dispersión de semillas de estas especies, otros aspectos de su reproducción son desconocidos. En este trabajo estudiamos su sistema reproductivo, la calidad del servicio de polinización que reciben y los visitantes florales. Todas las especies son xenógamas. Una especie (M. laetevirens) es anemófila y las demás son visitadas principalmente de DÃpteros, Himenópteros y Lepidópteros. El servicio de polinización parece insuficiente en la mayorÃa de las especies nativas. A. edulis y B. salicifolius produjeron menos frutos en condiciones naturales que cuando se polinizó las flores con polen de otro individuo y sólo O. acutifolia y las dos especies exóticas mostraron cargas polÃnicas estigmáticas suficientes para alcanzar el máximo de producción de semillas. Una posible explicación de los patrones encontrados podrÃa ser la reducción de las poblaciones de las especies nativas producida por la expansión de las exóticas, en particular de L.lucidum
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