The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Michael Wink - One of the best experts on this subject based on the ideXlab platform.
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Diversity of Secondary Metabolites in the Genus Silene L. (Caryophyllaceae)—Structures, Distribution, and Biological Properties
Diversity, 2014Co-Authors: Nilufar Mamadalieva, Rene Lafont, Michael WinkAbstract:The genus Silene (family Caryophyllaceae) comprises more than 700 species, which are widely distributed in Temperate Zones of the Northern Hemisphere, but are also present in Africa and have been introduced in other continents. Silene produces a high diversity of secondary metabolites and many of them show interesting biological and pharmacological activities. More than 450 compounds have been isolated; important classes include phytoecdysteroids (which mimic insect molting hormones), triterpene saponins (with detergent properties), volatiles, other terpenoids and phenolics. This review focusses on the phytochemical diversity, distribution of Silene secondary metabolites and their biological activities.
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Selection on a eumelanic ornament is stronger in the tropics than in Temperate Zones in the worldwide-distributed barn owl.
Journal of evolutionary biology, 2008Co-Authors: Alexandre Roulin, Michael Wink, Nicolas SalaminAbstract:Spatial variation in the pattern of natural selection can promote local adaptation and genetic differentiation between populations. Because heritable melanin-based ornaments can signal resistance to environmentally mediated elevation in glucocorticoids, to oxidative stress and parasites, populations may vary in the mean degree of melanic coloration if selection on these phenotypic aspects varies geographically. Within a population of Swiss barn owls (Tyto alba), the size of eumelanic spots is positively associated with survival, immunity and resistance to stress, but it is yet unknown whether Tyto species that face stressful environments evolved towards a darker eumelanic plumage. Because selection regimes vary along environmental gradients, we examined whether melanin-based traits vary clinally and are expressed to a larger extent in the tropics where parasites are more abundant than in Temperate Zones. To this end, we considered 39 barn owl species distributed worldwide. Barn owl species living in the tropics displayed larger eumelanic spots than those found in Temperate Zones. This was, however, verified in the northern hemisphere only. Parasites being particularly abundant in the tropics, they may promote the evolution of darker eumelanic ornaments.
Osvaldo E Sala - One of the best experts on this subject based on the ideXlab platform.
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potential effects of climate change on the Temperate Zones of north and south america
Revista Chilena de Historia Natural, 2004Co-Authors: William K Lauenroth, Jose M Paruelo, Howard E Epstein, Ingrid C Burke, Martin R Aguiar, Osvaldo E SalaAbstract:Bajo condiciones actuales, extensas areas de las zonas templadas del oeste de America del Norte y del sur de America del Sur tienen regimenes climaticos aridos a subhumedos, que son vulnerables a cambios climaticos inducidos por actividades humanas. Predicciones obtenidas a partir de modelos de circulacion global bajo una duplicacion del CO2 atmosferico sugieren grandes cambios en temperatura media anual, y cambios pequenos o nulos en la precipitacion media anual y la proporcion de precipitacion estival. Nuestro objetivo fue evaluar como las predicciones de cambio climatico obtenidas de modelos de circulacion global influiran sobre los patrones climaticos, e inferir a partir de ello la distribucion de los ecosistemas de las zonas templadas de America del Norte y del Sur. Calculos de deficit hidrico anual sugieren que, debido al cambio climatico, se duplicara el area afectada por condiciones muy secas. Esta expansion ocurrira en las cercanias de las zonas aridas actuales. Calculos mensuales de deficit hidrico sugieren que aproximadamente la mitad de la zona templada de cada continente se ve afectada por al menos un mes de deficit. Bajo un clima con doble CO2, estas areas se expandirian y cubririan hasta 77 % de las areas templadas de America del Norte y hasta 80 % de America del Sur. Los cambios en la distribucion de ecosistemas resultantes probablemente seran debidos a la expansion de los desiertos a expensas de los pastizales en America del Norte y del Sur, y la expansion de los pastizales a expensas de los bosques deciduos y boreales en America del Norte. Nuestros analisis asumen que los cambios climaticos futuros estaran abarcados por las predicciones de los tres escenarios de duplicacion de CO2 que utilizamos. La situacion mas probable es que los cambios reales, si es que ocurren, seran distintos a nuestros escenarios. Por lo tanto, nuestros analisis deberan interpretarse como indicaciones de la sensibilidad de partes de las zonas templadas de America del Norte y del Sur a aumentos de temperatura. La principal conclusion de nuestros analisis es que cualquier aumento de temperatura debido a cambios climaticos resultara en una expansion de las porciones mas aridas de ambos continentes
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regional climatic similarities in the Temperate Zones of north and south america
Journal of Biogeography, 1995Co-Authors: Jose M Paruelo, William K Lauenroth, Howard E Epstein, Ingrid C Burke, Martin R Aguiar, Osvaldo E SalaAbstract:We performed an analysis of the climatic patterns of the Temperate Zones in North and South America using a global database of monthly precipitation and temperature. Three synthetic variables, identified by a principal component analysis (PCA) of the monthly data, were used: mean annual precipitation, mean annual temperature and the proportion of the precipitation falling during summer. We displayed the spatial gradient of the three variables by constructing a com- posite colour raster image. We used a parallelepiped classification algorithm to locate areas in both continents that are climatically similar to five North American Long Term Ecological Research sites and to two South American long- term ecological research sites. The same algorithm was used to identify areas in South America which are climatically similar to some of the major grassland and shrubland types of North America. There is substantial overlap between the climates of North and South America. Most of the climatic patterns found in South America are well represented in North America. How- ever, there are certain climates in North America that are not found in South America. An example is a climate with relatively low mean annual temperature and high summer precipitation. The climatic signatures of three North American LTER sites (Cedar Creek, CPER and Sevilleta) were not found in South America. The climatic signatures of two LTER sites (Konza and Jornada) had some representation in South America. Two South American research sites (Rio Mayo and Las Chilcas) were well represented climatically in North America. The climates of six out of seven selected North American grassland and shrubland types were represented in South America. The northern mixed prairie type was not represented climatically in South America. Our analysis sug- gests that comparisons of North and South America can provide a powerful test of climatic control over vegetation.
Gerhard Zotz - One of the best experts on this subject based on the ideXlab platform.
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vascular epiphytes in the Temperate Zones a review
Plant Ecology, 2005Co-Authors: Gerhard ZotzAbstract:Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in Temperate forests is little appreciated. This review summarises the available information on epiphytism in the Temperate Zones ( g 23.5 degrees latitude), which has not been reviewed comprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the Temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum: Temperate epiphyte communities are generally dominated by ferns and fern-allies. Other,Temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and,diversity (water scarcity or low temperatures) are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.
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Vascular epiphytes in the Temperate Zones–a review
Plant Ecology, 2005Co-Authors: Gerhard ZotzAbstract:Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in Temperate forests is little appreciated. This review summarises the available information on epiphytism in the Temperate Zones ( g 23.5 degrees latitude), which has not been reviewed comprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the Temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum: Temperate epiphyte communities are generally dominated by ferns and fern-allies. Other,Temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and,diversity (water scarcity or low temperatures) are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.
Nilufar Mamadalieva - One of the best experts on this subject based on the ideXlab platform.
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Diversity of Secondary Metabolites in the Genus Silene L. (Caryophyllaceae)—Structures, Distribution, and Biological Properties
Diversity, 2014Co-Authors: Nilufar Mamadalieva, Rene Lafont, Michael WinkAbstract:The genus Silene (family Caryophyllaceae) comprises more than 700 species, which are widely distributed in Temperate Zones of the Northern Hemisphere, but are also present in Africa and have been introduced in other continents. Silene produces a high diversity of secondary metabolites and many of them show interesting biological and pharmacological activities. More than 450 compounds have been isolated; important classes include phytoecdysteroids (which mimic insect molting hormones), triterpene saponins (with detergent properties), volatiles, other terpenoids and phenolics. This review focusses on the phytochemical diversity, distribution of Silene secondary metabolites and their biological activities.
Brett A. Neilan - One of the best experts on this subject based on the ideXlab platform.
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increased incidence of cylindrospermopsis raciborskii in Temperate Zones is climate change responsible
Water Research, 2012Co-Authors: Rati Sinha, Michele A. Burford, Leanne A. Pearson, Timothy W. Davis, Philip T. Orr, Brett A. NeilanAbstract:The bloom-forming, toxic cyanobacterium, Cylindrospermopsis raciborskii exhibits global distribution. In recent years both the occurrence and dominance of this species, particularly in Temperate regions, has increased. Whilst this may be due to increased sensitivity of analytical detection methods or more rigorous sampling routines, it is possible that this expansion has been assisted by a number of changing conditions in these environments. The geographical expansion of both the organism and toxin production can be attributed to phenomena such as eutrophication and climate change. In this review, we discuss the occurrence of C. raciborskii with respect to current literature against the backdrop of increasing global temperatures. Critically, we identify a concerning trend between the geographical spread of this organism and global climate change.
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Increased incidence of Cylindrospermopsis raciborskii in Temperate Zones – Is climate change responsible?
Water research, 2011Co-Authors: Rati Sinha, Michele A. Burford, Leanne A. Pearson, Timothy W. Davis, Philip T. Orr, Brett A. NeilanAbstract:The bloom-forming, toxic cyanobacterium, Cylindrospermopsis raciborskii exhibits global distribution. In recent years both the occurrence and dominance of this species, particularly in Temperate regions, has increased. Whilst this may be due to increased sensitivity of analytical detection methods or more rigorous sampling routines, it is possible that this expansion has been assisted by a number of changing conditions in these environments. The geographical expansion of both the organism and toxin production can be attributed to phenomena such as eutrophication and climate change. In this review, we discuss the occurrence of C. raciborskii with respect to current literature against the backdrop of increasing global temperatures. Critically, we identify a concerning trend between the geographical spread of this organism and global climate change.
