The species of Scolytinae subfamily have a worldwide distribution, and are found mainly in the Neo-tropic regions. They usually dominate the communities of wood borer insects. The aim of the present study was to determine the diversity among Scolytinae species associated with balsa, teak, rubber and gamhar plantations located in the humid tropical zone of the Ecuadorian littoral. In each plantation seven flight interception traps containing an ethanol / gel mixture were installed, with a collection frequency of 15 days for three months in the dry period. A total of 1437 specimens were collected, represented by Xyleborini, Cryphalini, Corthylini and Ipini tribes. In the four plantations, 18 species of Scolitids were collected, of which 16 were recorded in the balsa plantation, while in the other plantations 10 to 12 species were found. The most abundant Scolitids were Hypothenemus spp., Corthylus spp., Xyleborus affinis, Xyleborinus bicornatulus and Premnobium cavipennis. The Shannon-Wiener diversity index was higher in the balsa culture (H’= 2.37) and lower in Teak (H’= 1.57). The Jaccard similarity index was higher among the teak and rubber plantations (Cj = 0.9090) while the balsa plantation obtained less similarity with respect to the other three plantations. The greatest diversity of Scolitids was recorded in the balsa plantation, which is a native species, unlike the other forest species, which are exotic, indicating that the diversity would be influenced by the host tree and the location where they are found.

SummaryThe plant-assisted removal of phenol, with special emphasis on the effects of this compound on some plant's physiological parameters, was investigated. Hydroponic cultures of alfalfa (Medicago sativa L., var. Romagnola) were employed as a model system. These cultures were exposed to two phenol concentrations: 100 and 500 mg/l. A first order kinetic approach was used to describe the removal of phenol from the solution. After 30 days of cultivation, the initial amount of phenol (100 mg/l) was reduced to non-detectable levels in the presence of plants. In the absence of plants, 20% of phenol remained in the solution. The half-life of phenol was reduced from 7.2 to 4.5 days in the presence of plants. After 25 days, the initial amount of 500 mg/l of phenol was reduced to non-detectable levels in the presence of plants not previously exposed to phenol and to approximately 20% with plants previously exposed to the contaminant. In the absence of plants, almost 40% remained in the solution. The presence of plants reduced the half-life of phenol from 18.3 days to 10.4 in the case of plants previously exposed and to 7.8 days in the case of plants without previous contact. Chlorophyll contents in alfalfa leaves of plants exposed to 100 mg/l of phenol were similar to those of control plants and a decrease in total chlorophyll content was observed when plants were exposed to 500 mg/l of phenol. The activity of soluble peroxidases of the roots increased in the presence of 100 mg/l of phenol but the amount of 500 mg/l had a negative effect on the peroxidase fraction. No changes were observed in the case of the ionically-bound cell wall fraction. The growth index of the plants exposed to 100 mg/l of phenol was comparable to that of non-exposed plants, while this parameter was negatively affected in the case of plants exposed to 500 mg/l of phenol. Although alfalfa plants were able to survive an exposure to 500 mg/l of phenol, their physiological parameters and their removal capacity were negatively affected.

Alfalfa (Medicago sativa L.) and other plants bearing an important root system have been shown to be effective in the removal of organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Phenanthrene is one of the main contaminants arising from the petrochemical industry and is included in the USEPA's list of priority toxic pollutants. Hydroponic cultures of alfalfa were employed as a model system to evaluate their capability of removing phenanthrene and to study the plantpollutant interaction without the interference of a soil matrix. The removal of phenanthrene was followed over a period of 30 days. The half-life of phenanthrene in hydroponics (initial concentration 50 mg L -1 ) was reduced 2.7 times when plants were present. Growth index, chlorophyll content of leaves, and peroxidase activity of the roots of plants exposed to phenanthrene were lower than the corresponding values of nonexposed plants. Phenanthrene produced an acute negative effect on the total bacterial counts but also caused an increase in degraders/total bacteria ratio. The Ames Salmonella plate incorporation assay was employed to screen for potential genotoxic metabolites, which could be generated by metabolic activation of the parent compound. None of the samples exhibited a positive response. While lack of a positive response to this test is not a definitive evidence of the absence of genotoxic substances, these results suggest that the plant-assisted removal of phenanthrene merits further investigation.

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