740 research outputs found
Life history and mating systems select for male biased parasitism mediated through natural selection and ecological feedbacks
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordMales are often the 'sicker' sex with male biased parasitism found in a taxonomically diverse range of species. There is considerable interest in the processes that could underlie the evolution of sex-biased parasitism. Mating system differences along with differences in lifespan may play a key role. We examine whether these factors are likely to lead to male-biased parasitism through natural selection taking into account the critical role that ecological feedbacks play in the evolution of defence. We use a host-parasite model with two-sexes and the techniques of adaptive dynamics to investigate how mating system and sexual differences in competitive ability and longevity can select for a bias in the rates of parasitism. Male-biased parasitism is selected for when males have a shorter average lifespan or when males are subject to greater competition for resources. Male-biased parasitism evolves as a consequence of sexual differences in life-history that produce a greater proportion of susceptible females than males and therefore reduce the cost of avoiding parasitism in males. Different mating systems such as monogamy, polygyny or polyandry did not produce a bias in parasitism through these ecological feedbacks but may accentuate an existing bias.Flora S. Bacelar acknowledges support from the Balaric Government, and from Spanish MICINN and FEDER through project FISICOS (FIS200760327) and to Emílio Hernández-García for reading the article and useful discussions. Andrew White is supported by a Royal Society of Edinburgh and Scottish Government Support Research Fellowship. Mike Boots is supported by a Leverhulme Trust Fellowship
Análise da expansão da agricultura de grãos na região de Santarém e Belterra, Oeste do estado do Pará.
The images obtained from orbital platforms have been used for the analysis of many occupation processes of the Amazon region along the years. Nevertheless, analyses that have only one date of passage portray just a point in time and, for that, do not explain the occupation process of the region. The evolution of the mechanical agriculture in the towns of Belterra and Santarém, in the west side of Pará state, is causing a series of conflicts between the producers and the environmental movements because of the hypothesis of the expansion of the cultivated area in detriment of the areas of forest formation. Through a time series analysis that uses images from the sensors MSS and TM Landsat from 1975, 1986, 1997, 1999, 2004 and 2005, using digital classification and an intense field work, it was possible to observe the dynamic of the use and the discovery of the land. The results show that there was a reduction of 25% of the forest in the last 30 years. Although the main landscape is the forest formation, it was found that the use of the land with the most occupied area are the regions destinated to the agriculture and cattle activities and which are related to the producers of different levels of technology who try to combine a series of productive systems, aiming the diversity of the natural resources. In addition, it was possible to observe that, unlike other regions in the Amazon, the areas of secondary vegetation presented a high growth in the analyzed time period. Finally it is noticed that the culture of grains was implemented, mostly, in areas that were altered and used for pasture, secondary vegetation and agriculture and livestock activities (related to small and medium producers), having been converted a total of 435 km2 of forest from the year of 1999 to 2004, representing 8% of the total planted area in that year. Although we notice a smaller impact in the environmental context, the direct conversion of the agriculture and livestock class into the grain plantation seems to indicate a process of land concentration and migration of smallholder farmers to the urban areas and/ or new fronts of occupation. This social impact, already observed in Santarém suburbs, should be object of study for the government, mainly concerning the elaboration and implementation of a specific agricultural politics for the Amazon and should enable the smallholder farmer the maintenance of his land and food production
Composição quantitativa de pigmentos durante o desenvolvimento de frutos camu-camu (myrciaria dubia).
40Ar-39Ar age of the copper mineralization at riacho do pontal IOCG district and detrital zircon U–Pb ages of paragneiss host rocks
Geological, structural and metallogenetic characteristics related to the Proterozoic Riacho do Pontal iron-oxide copper gold (IOCG) mineral systems in northeast Brazil have been reinterpreted recently and there is an ongoing discussion regarding their genetic model and associated tectonic setting. The mineralization in the Riacho do Pontal district is represented by small copper deposits strongly controlled by the structural features of the basement rocks. Hydrothermal biotite associated with the copper mineralization has a 40Ar-39Ar of ca. 691 Ma, indicating a probable late Neoproterozoic age for the main mineralization event. Detrital zircon grains from the host rock show that the sedimentary protolith is younger than ca. 2035 Ma and was probably deposited in a convergent setting. Our results help to understand the emplacement of this deposit in the tectonic context of the Riacho do Pontal Belt
Injurias mecânicas e seus efeitos na qualidade pós-colheita de frutos de camu-camu (Myrciaria dubia H. B. K. (Mcvough).
Genotype, Environment and Management Practices on Red/ Dark-Colored Fruits Phenolic Composition and Its Impact on Sensory Attributes and Potential Health Benefits
Phenolic compounds are secondary metabolites abundant in our diet. These compounds may affect positively or negatively the sensory characteristics of food with important impacts on color, flavor, and astringency. An adequate consumption of phenolic compounds may also offer health benefits. After the consumption of fruits, the colon is the main site of microbial fermentation, where high molecular weight phenolic compounds are transformed into low molecular weight phenolic compounds such as phenolic acids or lactone structures by intestinal microbiota, which produce metabolites with biological and antioxidant activity, with evidence on health benefits for humans. A large amount of different phenolic compounds are responsible for physicochemical and sensory characteristics of table grapes and wines. Also, sweet cherry (Prunus avium L.) is one of the most popular temperate table fruits; they contain flavonoids, flavan‐3‐ols, and flavonols in addition to non‐flavonoid compounds. Anthocyanins are the major polyphenols in blueberries, and this group of phytochemicals is thought to be responsible for many of the health benefits of berry consumption. Therefore, considering the importance of red/dark‐colored fruits phenolic composition, the purpose of this chapter is to make a review of the most recent publications about these fruits’ phenolic composition and their impact on sensorial properties as well as the effect of microorganisms on fruit phenolic composition
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