970 resultados para Trade competition defense


Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fruit traits evolve in response to an evolutionary triad between plants, seed dispersers, and antagonists that consume fruits but do not disperse seeds. The defense trade-off hypothesis predicts that the composition of nutrients and of secondary compounds in fruit pulp is shaped by a trade-off between defense against antagonists and attraction to seed dispersers. The removal rate model of this hypothesis predicts a negative relationship between nutrients and secondary compounds, whereas the toxin-titration model predicts a positive relationship. To test these alternative models, we evaluated whether the contents of nutrients and secondary compounds can be used to predict fruit removal by mutualists and pathogens in 14 bird-dispersed plants on a subtropical island in São Paulo state, southeastern Brazil. We selected eight to ten individuals of each species and prevented fruit removal by covering four branches with a net and left fruits on four other branches available to both, vertebrate fruit consumers and pathogens. The persistence of ripe fruits was drastically different among species for bagged and open fruits, and all fruit species persisted longer when protected against seed dispersers. We found that those fruits that are quickly removed by vertebrates are nutrient-rich, but although the attack rate of pathogens is also high, these fruits have low contents of quantitative defenses such as tannins and phenols. Thus, we suggest that the fruit removal rate by seed dispersers is the primary factor selecting the levels of fruit defense. Likewise, nutrient-poor fruits have low removal of seed dispersers and low probability of attack by pathogens. These species retain ripe fruits in an intact condition for a prolonged period because they are highly defended by secondary compounds, which reduce overall attractiveness. However, this strategy might be advantageous for plants that depend on rare or unreliable dispersers.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes Bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This document provides an overview of the most relevant developments in United States trade policy relating to Latin America and the Caribbean in 2002. U.S. policy continued to promote trade liberalization through advancing negotiations on multiple fronts- globally (WTO), regionally (FTAA) and bilaterally or sub regionally- with a view that the various negotiations are mutually reinforcing and seek to create a constructive competition for liberalization" among trade partners. The passage of Trade Promotion Authority (TPA) included in the Trade Act of August 2002 enhanced the U.S. Administration's ability to negotiate trade agreements. It provided an impetus to conclude bilateral negotiations with Chile as well as to advance a number of trade agreements currently under negotiation, including negotiations toward the Free Trade Area of the Americas (FTAA) and bilateral negotiations with Central America. The Trade Act also renewed the Generalized System of Preferences, extended the Caribbean Trade Partnership Act by liberalizing apparel provisions and augmented the Andean Trade Preference Act, increasing the list of duty free products. On the multilateral front, in partial fulfillment of the Doha mandate, the U.S. tabled in 2002 two comprehensive proposals for the reduction of trade barriers on agricultural and non-agricultural goods. Along with these trade liberalizing proposals, the U.S. Administration imposed temporary safeguard measures on key steel products to provide relief to the sectors of the steel industry that have been most affected by import surges. In addition, the U.S. Congress passed the 2002 Farm Security and Rural Investment Act that substantially increased U.S. domestic farm subsidies to shield domestic farm producers from competition from subsidized products from abroad."

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Includes bibliography