Pigeon navigation: Charcoal filter removes relevant information from environmental air

Summary Homing pigeons were displaced and kept until they were released in airtight containers ventilated with environmental air that could be passed through: (a) a filter made of fiberglass paper retaining large portions of the solid and liquid aerosol particles, (b) an additional filter consisting of activated charcoal, or (c) no filter (controls). Before its release, each bird was taken out of the container, and its olfactory epithelium was immediately anesthetized by lidocaine (Xylocaine). Thus, neither experimentals nor controls were able to smell while their initial orientation behavior was being observed.The controls' initial bearings were better homeward-oriented than those of pigeons ventilated with charcoal-filtered air in 14 of 17 releases conducted in Italy and Germany, at distances of 24–155 km. In the final analysis, the bearings of the charcoal-filter birds did not show any relation to the direction toward home, whereas those of the controls did. Pigeons ventilated with air that had passed through only the paper filter did not behave noticeably differently from control pigeons.It is concluded that the material bases of olfactory navigation in pigeons are substances dispersed in the atmosphere, most probably in a molecular state.     

Male philopatry,extra-pack copulations and inbreeding avoidance in Ethiopian wolves (Canis simensis)

Monogamous pairings have been regarded as the fundamental social unit in all canid species, including those living in packs. In Ethiopian wolves, however, habitat saturation limits dispersal, which raises the question of whether they avoid inbreeding and, if so, by what mechanism. In two study areas Ethiopian wolf packs had stable memberships. Each pack comprised two to eight adult males, one to three adult females, including a clear-cut dominant individual of each sex, together with one to six yearlings and up to six pups (n = 9 packs). Males remained in their natal packs, apparently throughout their lives. Some females also failed to disperse while others dispersed in their second or third year and became floaters. Dominant females monopolized breeding, and were succeeded either by their most dominant daughters (three cases) or by floaters (two cases). In the former case there is potential for incest; however, 70% of 30 copulations observed were between the dominant female of one pack and a male from an adjoining pack. In Ethiopian wolves, under conditions where dispersal is constrained and the potential for inbreeding is high, extra-pack matings (and associated multiple paternity) result in outbreeding. We raise the possibility that extra-pair copulations may be widespread in canid societies and that the monogamy supposedly fundamental to the family may be more sociological than genetic. Received: 15 October 1994/Accepted after revision: 9 December 1995     

Heavy metals and organic carbon in sediments from the Tuy River basin,Venezuela

The Tuy River basin, located in north-central Venezuela with an annual average temperature of 27°C and precipitation of 140 cm, was selected to conduct a geochemical study of bottom sediments, with the object of establishing the natural and human influences in the abundance and distribution of Fe, Mn, Cr, Co, Cu, Ni, Pb, Zn and organic carbon. The basin is lithologically divided into two sub-basins, north and south. The north sub-basin drains a iow-grade metasedimentary terrain with a population density of 800 persons km^–2 and approximateiy 600 industrial sites, while the south sub-basin in underlain by metavolcanic and ultramafic rocks, with a population density of less than 10 persons km^–2.Stream bottom sediment samples (150) were collected during the years of 1979–1986 in 16 unpolluted sites and 13 polluted sites. The sediments were air dried at room temperature and sieved through a 120 stainless steel mesh (125 m). Samples of grain size smaller than 125 m were analysed, the heavy metals being determined by atomic absorption spectrometry and the organic carbon (Corg) by dry combustion.The higher concentrations of heavy metals and organic carbon found in the pristine areas were in the south sub-basin, especially in those areas with higher annual precipitation and tropical forest. This indicated that the metavolcanic and ultramafic rocks yield higher concentrations of heavy metals than the metasedimentary rocks. It was also noted that the higher concentrations of Cr and Ni are associated with the ultramafic rocks. The results obtained from the sediment samples collected in the polluted sites showed that the elements Pb, Zn and Corg are enriched up to 4 times as a result of ail the human activities taking place in the basin. Organic carbon is an excellent indicator of domestic wastewater, Pb and Zn are good indicators of the automotive traffic and industrial effluents. The concentrations of each heavy metal did not show any significant correlation with grain size fractions; however, the concentration of organic carbon did show a negative correlation with grain size. The lithological, climatic and vegetation influence in the abundance of heavy metals and organic carbon in stream sediments clearly indicates the necessity of establishing background levels for the area under study when carrying out studies in environmental geochemistry.     

The effects of heavy metal contamination on the soil arthropod community of a shooting range

Soils in clay pigeon shooting ranges can be seriously contaminated by heavy metals. The pellets contained in ammunition are composed of Pb, Sb, Ni, Zn, Mn and Cu. The total concentrations of these metals in soils, and the effects of their increasing levels on the arthropod community were investigated at seven sampling sites in a clay pigeon shooting range and compared with two controls. Research revealed that the spatial distribution of Pb and Sb contamination in the shot-fall area was strongly correlated with the flight path of the pellets. Ordination obtained through Redundance Analysis showed that Collembola, Protura and Diplura were positively correlated with major detected contaminants (Pb, Sb), while Symphyla showed a negative correlation with these pollutants. Determination of the soluble lead fraction in soil, and of its bioaccumulation in the saprophagous Armadillidium sordidum (Isopoda) and the predator Ocypus olens (Coleoptera), showed that a significant portion of metallic Pb from spent pellets is bioavailable in the soil and can be bioaccumulated by edaphic organisms, entering the soil trophic network, but without biomagnification.     

Treatment of chlorinated solvents by TiO2 photocatalysis and photo-Fenton: influence of operating conditions in a solar pilot plant

Titanium dioxide photocatalysis (using 20 0mg l(-1) of TiO2), under aerobic and anaerobic conditions, and photo-Fenton (2 and 56 mg l(-1) iron) were applied to the treatment of different NBCS (non-biodegradable chlorinated solvents), such as dichloroethane, dichloromethane and trichloromethane dissolved in water at 50 mg l(-1). All the tests were performed in a 35-l solar pilot plant with compound parabolic collectors (CPCs) under natural illumination. The two solar treatments were compared with attention to chloride release and TOC mineralisation, as the main parameters. Photo-Fenton was found to be the more appropriate treatment for these compounds, assuming volatilisation as a drawback of photocatalytic degradation of NBCS dissolved in water. In this context, several operating parameters related to NBCS degradation, e.g., treatment time, temperature, hydrogen peroxide consumption and volatility of parent compounds are discussed. The correct choice of operating conditions can very often diminish the problem of volatilisation during treatment.     

On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.     

Wheat volatile emissions modified by top-soil chemical characteristics and herbivory alter the performance of neighbouring wheat plants

Plant emission of volatile organic compounds (VOCs) has a significant impact on arthropods and plants and alters important functions in the agroecosystems. Three field source–sink microcosm experiments evaluated variation in wheat plants volatile emissions and its impact on neighbouring wheat plants’ performance caused by genotype, aphid herbivory and soil nutrient availability due to different cropping histories. An electronic nose detected qualitative differences in volatile emissions. Two of the experiments established the source–sink relationships forcing the volatiles through pipes. In these experiments wheat genotype was introduced as a variable of the source plants. In the third experiment, the emissions of volatiles dispersed naturally affecting the neighbourhood only by proximity and wheat genotype was a controlled factor. Plant genotype, aphid attack and soil chemical changes caused by different cropping histories affected wheat volatile emissions despite independent variations in plant biomass or resource allocation. This is the first report of changes in distant plant biomass according to neighbouring plant genotype and agricultural history. Wheat VOCs emissions were associated with changes in soil organic C, Ca, Mg, total nitrogen and cation exchange capacity caused by the different cropping histories of the soils tested. Variability in total biomass and resource allocation increased due to changes in VOCs emissions promoted by longer cropping history or aphid feeding in two genotypes. When volatiles were naturally dispersed into the neighbourhood, tiller weight in the sink individuals depended on plant genotype and cropping history of its neighbours (i.e. VOCs source). These findings highlight that ecological and environmental consequences of agricultural practices are more complex than normally thought.     

Effects of Amazonian flying rivers on frog biodiversity and populations in the Atlantic rainforest

Given the speed at which humans are changing the climate, species with high degrees of endemism may not have time to avoid extinction through adaptation. We investigated through teleconnection analysis the origin of rainfall that determines the phylogenetic diversity of rainforest frogs and the effects of microclimate differences in shaping the morphological traits of isolated populations (which contribute to greater phylogenetic diversity and speciation). We also investigated through teleconnection analysis how deforestation in Amazonia can affect ecosystem services that are fundamental to maintaining the climate of the Atlantic rainforest biodiversity hotspot. Seasonal winds known as flying rivers carry water vapor from Amazonia to the Atlantic Forest, and the breaking of this ecosystem service could lead Atlantic Forest species to population decline and extinction in the short term. Our results suggest that the selection of morphological traits that shape Atlantic Forest frog diversity and their population dynamics are influenced by the Amazonian flying rivers. Our results also suggest that the increases of temperature anomalies in the Atlantic Ocean due to global warming and in the Amazon forest due to deforestation are already breaking this cycle and threaten the biodiversity of the Atlantic Forest hotspot.     

Plant-mediated and nonadditive effects of two global change drivers on an insect herbivore community

Warmer temperatures can alter the phenology and distribution of individual species. However, differences across species may blur community-level phenological responses to climate or cause biotic homogenization by consistently favoring certain taxa. Additionally, the response of insect communities to climate will be subject to plant-mediated effects, which may or may not overshadow the direct effect of rising temperatures on insects. Finally, recent evidence for the importance of interaction effects between global change drivers suggests that phenological responses of communities to climate may be altered by other drivers. We used a natural temperature gradient (generated by elevation and topology), combined with experimental nitrogen fertilization, to investigate the effects of elevated temperature and globally increasing anthropogenic nitrogen deposition on the structure and phenology of a seminatural grassland herbivore assemblage (lepidopteran insects). We found that both drivers, alone and in combination, severely altered how the relative abundance and composition of species changed through time. Importantly, warmer temperatures were associated with biotic homogenization, such that herbivore assemblages in the warmest plots had more similar species composition than those in intermediate or cool plots. Changes in herbivore composition and abundance were largely mediated by changes in the plant community, with increased nonnative grass cover under high treatment levels being the strongest determinant of herbivore abundance. In addition to compositional changes, total herbivore biomass more than doubled under elevated nitrogen and increased more than fourfold with temperature, bearing important functional implications for herbivores as consumers and as a prey resource. The crucial role of nonnative plant dominance in mediating responses of herbivores to change, combined with the frequent nonadditive (positive and negative) effects of the two drivers, and the differential responses of species, highlight that understanding complex ecosystem responses will benefit from multifactor, multitrophic experiments at community scales or larger.