Sexual and natural selection in a continuous time model

We call sexual selection the selection attributable only to the mating system, to distinguish it from other forms of selection (i.e. viability or fertility) which we call natural selection. We introduce a new continuous time model of sexual selection and we explore its relationship with natural selection. This model is an extension of the model proposed by Hoppensteadt [Hoppensteadt, F., 1977. Mathematical Theories of Populations: Demographics, Genetics and Epidemics. SIAM] and considers the three genotypes determined by two alleles in a locus, each with its own mortality and fertility rates, and the respective mating preferences.     

Extractable atrazine and its metabolites in agricultural soils from the temperate humid zone

Extractable atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) were evaluated in agricultural soils from the temperate humid zone (Galicia, NW Spain) under laboratory conditions. The experiment was performed with five soils with different properties (organic C, soil texture and atrazine application history), both unamended and treated with atrazine at field application rate. Measurements of the atrazine compounds were made at different time intervals (1, 3, 6, 9 and 12 weeks) during a 3-month incubation period. Results showed that only hydroxyatrazine was detected in the extractable fraction of the unamended soils, with values remaining relatively constant throughout the incubation period. Atrazine addition notably increased the concentration of the parent compound and its degradation products; deisopropylatrazine and hydroxyatrazine were the main metabolites detected in the extractable fraction of the treated soils, whereas deethylatrazine was not detected. After 7 days incubation, values of total extractable residues, expressed as percentage of initially added atrazine, ranged from 75 to 86% (25–68% of atrazine, 7–11% of hydroxyatrazine and 9–57% of deisopropylatrazine). The values decreased rapidly during the first 3 weeks of incubation, showing values of 2–8% in soils with higher atrazine application and from 28 to 30% in soils with lower application history. At the end of the incubation, 2–8% of total extractable residues were still detected (0–4% of atrazine, 2–3% of hydroxyatrazine and 0–2% of deisopropylatrazine), indicating a residual effect of atrazine addition. These variations in the extractable fraction indicated that most added atrazine was rapidly degraded, especially in soils with higher application history.     

Multiple antibiotic resistance patterns of rhizospheric bacteria isolated from Phragmites australis growing in constructed wetland for distillery effluent treatment

Susceptibility patterns of 12 different antibiotics were investigated against rhizospheric bacteria isolated from Phragmites australis from three different zones i.e. upper (0-5 cm), middle (5-10 cm), lower (10-15 cm) in constructed wetland system with and without distillery effluent. The major pollutants of distillery effluent were phenols, sulphide, heavy metals, and higher levels of biological oxygen demand (BOD), chemical oxygen demand (COD) etc. The antibiotic resistance properties of bacteria were correlated with the heavy metal tolerance (one of distillery pollutant). Twenty-two species from contaminated and seventeen species from non-contaminated site were tested by agar disc-diffusion method. The results revealed that more than 63% of total isolates were resistance towards one or more antibiotics tested from all the three different zones of contaminated sites. The multiple-drug resistance property was shown by total 8 isolates from effluent contaminated region out of which 3 isolates were from upper zone, 3 isolates from middle zone and 2 isolates were from lower zone. Results indicated that isolates from contaminated rhizosphere were found more resistant to antibiotics than isolates from non-contaminated rhizosphere. Further this study produces evidence suggesting that tolerance to antibiotics was acquired by isolates for the adaptation and detoxification of all the pollutants present in the effluent at contaminated site. This consequently facilitated the phytoremediation of effluent, which emerges the tolerance and increases resistance to antibiotics.     

Abundance and diversity of the phyllosphere bacterial communities of Mediterranean perennial plants that differ in leaf chemistry

Summary.  We studied the epiphytic bacterial communities of the summer leaves of eight perennial species naturally occurring in a Mediterranean ecosystem. The species differ in essential-oil content (from rich in essential oil to non-producers) and composition, and also in life form (from herbaceous species to tall shrubs). We compared the epiphytic bacterial communities on the basis of (i) their abundance, (ii) their metabolic profile (derived by use of the BIOLOG Ecoplate system) and (iii) richness and diversity of substrates that they use, as a measure of functional diversity. Among all species, the aromatic Melissa officinalis was the most abundantly colonized. The bacterial communities on the leaves of the aromatic Myrtus communis, Calamintha nepeta and Melissa officinalis, and also of Cistus incanus catabolized all 31 substrates offered; those on the evergreen-sclerophyllous species, Arbutus unedo and Quercus coccifera, catabolized only 14 and 17 substrates, respectively. Carbohydrates were consistently used abundantly by all communities, whereas carboxylic acids were most variably used. On average, the group of aromatic plants scored higher regarding bacterial abundance, and richness and diversity of substrates used by the bacterial communities on their leaves; the lowest values for both substrate-use indices were recorded in A. unedo. Bacterial abundance or richness or diversity of substrates used did not vary with leaf oil content. Abundance was positively correlated with both substrate-use indices. Results support claims that the antimicrobial effects of essential oils are not exerted so much under natural conditions as reports based on biassays with pathogens usually show. Although essential oils play a part in the microbial colonization of the phyllosphere, it is not likely that inhibition of phyllosphere bacteria is essential oils’ primary role, at least in the Mediterranean environment.     

Sexual selection and the function of a melanin-based plumage ornament in polygamous penduline tits <Emphasis Type="Italic">Remiz pendulinus</Emphasis>

Melanin-based ornaments are often involved in signaling aggression and dominance, and their role in sexual selection is increasingly recognized. We investigated the functions of a melanin-based plumage ornament (facial ‘mask’) in male Eurasian penduline tits Remiz pendulinus in the contexts of male–male aggression, mating success, and parental care. The penduline tit is a passerine bird with a unique mating system in which both sexes may mate with several mates in a breeding season, and one (or both) parent deserts the clutch. Our study revealed that mask size of males is more likely an honest signal used by females in their mate choice decisions than a trait involved in male–male competition. First, mask size increased with both age and body condition, indicating that the mask may signal male quality. Second, males with larger masks paired more quickly and had more mates over the breeding season than males with smaller masks. Third, we found no evidence that male mask size signals male–male aggression or dominance during competitive encounters. The increased mating success of large-masked males, however, did not translate into higher reproductive success, as nestling survival decreased with mask size. Therefore, we conclude that there is either no directional selection on male mask size or males with larger masks receive indirect, long-term benefits.     

Global burned-land estimation in Latin America using MODIS composite data.

This paper presents results of the AQL2004 project, which has been develope within the GOFC-GOLD Latin American network of remote sensing and forest fires (RedLatif). The project intended to obtain monthly burned-land maps of the entire region, from Mexico to Patagonia, using MODIS (moderate-resolution imaging spectroradiometer) reflectance data. The project has been organized in three different phases: acquisition and preprocessing of satellite data; discrimination of burned pixels; and validation of results. In the first phase, input data consisting of 32-day composites of MODIS 500-m reflectance data generated by the Global Land Cover Facility (GLCF) of the University of Maryland (College Park, Maryland, U.S.A.) were collected and processed. The discrimination of burned areas was addressed in two steps: searching for "burned core" pixels using postfire spectral indices and multitemporal change detection and mapping of burned scars using contextual techniques. The validation phase was based on visual analysis of Landsat and CBERS (China-Brazil Earth Resources Satellite) images. Validation of the burned-land category showed an agreement ranging from 30% to 60%, depending on the ecosystem and vegetation species present. The total burned area for the entire year was estimated to be 153 215 km2. The most affected countries in relation to their territory were Cuba, Colombia, Bolivia, and Venezuela. Burned areas were found in most land covers; herbaceous vegetation (savannas and grasslands) presented the highest proportions of burned area, while perennial forest had the lowest proportions. The importance of croplands in the total burned area should be taken with reserve, since this cover presented the highest commission errors. The importance of generating systematic products of burned land areas for different ecological processes is emphasized.     

Resource limitation of bacterial production distorts the temperature dependence of oceanic carbon cycling

Our view of the effects of temperature on bacterial carbon fluxes in the ocean has been confounded by the interplay of resource availability. Using an extensive compilation of cell-specific bacterial respiration (BRi) and production (BPi), we show that both physiological rates respond to changing temperature in a similar manner and follow the predictions of the metabolic theory of ecology. Their apparently different temperature dependence under warm, oligotrophic conditions is due to strong resource limitation of BP, but not of BRi. Thus, and despite previous preconception, bacterial growth efficiency (BGE = BPi/[BPi + BRi]) is not directly regulated by temperature, but by the availability of substrates for growth. We develop simple equations that can be used for the estimation of bacterial community metabolism from temperature, chlorophyll concentration, and bacterial abundance. Since bacteria are the greatest living planktonic biomass, our results challenge current understanding of how warming and shifts in ecosystem trophic state will modify oceanic carbon cycle feedbacks to climate change.     

Benthic community response to petroleum-associated components in Arctic versus temperate marine sediments

We assessed the effects of crude oil and drill cuttings on sediment oxygen demand (SOD) of marine benthic communities from Arctic (Barents Sea) and temperate (Oslofjord) areas of the Norwegian continental shelf. Field-collected cores in both areas were subjected to three different treatments: two concentrations of hydrocarbon-contaminated sediments, and drill cuttings (DC). Cores were incubated for 21 days at 5°C (Barents Sea) and at 10°C (Oslofjord) during which SOD was measured five times. We observed significantly higher SOD in the high oil concentration (HOC) and DC treatments compared to control cores from the Arctic, but not in the temperate Oslofjord. No difference was observed between the low oil concentration (LOC) and control at either location. The clear differences in the response of Arctic benthic communities to petroleum compounds compared to temperate benthic communities is likely related to differences in community structure, sensitivity of individual taxa to petroleum-related compounds and different contamination history of the two study areas.     

Effect of chromium on the fatty acid composition of two strains of Euglena gracilis

The effect of hexavalent chromium on fatty acid composition was studied in two strains of Euglena gracilis; UTEX 753 (from the Culture Collection of Algae of Texas University, USA) and MAT (isolated from a highly polluted River). Both were grown in photoauxotrophic and photoheterotrophic conditions and exposed to two metal concentrations, one below and one above IC50. The high malondialdehyde (MDA) levels (3 to 7-fold) obtained with chromium concentration above IC50, suggested the existence of metal-induced lipid peroxidation. Total lipid content increased only with concentration below IC50, whereas it was inhibited by higher metal concentration. Photoheterotrophic control strains exhibited a significantly higher proportion of saturated and polyunsaturated fatty acids. Polyunsaturated acids were most affected by chromium, especially those related to chloroplast structures. Ultra-structure studies showed clear thylakoid disorganization in all treated cells. The results indicate that hexavalent chromium affects levels of fatty acids, especially those related to photosynthetic activity.     

Trace element concentrations in soils along urbanization gradients in the city of Wien, Austria

Urban soil is an important component of urban ecosystems. This study focuses on heavy metal contamination in soils of Wien (Austria) and results are compared to those for a few large European cities. We analysed the elemental contents of 96 samples of topsoil from urban, suburban and rural areas in Wien along a dynamic (floodplain forest) and a stable (oak–hornbeam forest) urbanization gradient. The following elements were quantified using ICP-OES technique: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Pb, P, S and Zn. For heavy metals PI (pollution index) values were used to assess the level of pollution. The PI values indicated high level of pollution by Pb in the suburban and rural area of stable gradient and in the urban area of dynamic gradient; moderate level of pollution was indicated for Cd in the urban area of stable gradient. The level of pollution was moderate for Co in the suburban and rural area of the stable gradient, and for Cu in suburban area of stable gradient, and urban area of dynamic gradient. The pollution level of Zn was moderate in all areas. Urban soils, especially in urban parks and green areas may have a direct influence on human health. Thus, the elemental analysis of soil samples is one of the best ways to study the effects of urbanization. Our results indicated that the heavy metal contamination was higher in Wien than in a few large European cities.