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Spatial Occurrence (spatial + occurrence)
Selected AbstractsWhere do Swainson's hawks winter?DIVERSITY AND DISTRIBUTIONS, Issue 5 2008Satellite images used to identify potential habitat ABSTRACT During recent years, predictive modelling techniques have been increasingly used to identify regional patterns of species spatial occurrence, to explore species,habitat relationships and to aid in biodiversity conservation. In the case of birds, predictive modelling has been mainly applied to the study of species with little variable interannual patterns of spatial occurrence (e.g. year-round resident species or migratory species in their breeding grounds showing territorial behaviour). We used predictive models to analyse the factors that determine broad-scale patterns of occurrence and abundance of wintering Swainson's hawks (Buteo swainsoni). This species has been the focus of field monitoring in its wintering ground in Argentina due to massive pesticide poisoning of thousands of individuals during the 1990s, but its unpredictable pattern of spatial distribution and the uncertainty about the current wintering area occupied by hawks led to discontinuing such field monitoring. Data on the presence and abundance of hawks were recorded in 30 × 30 km squares (n = 115) surveyed during three austral summers (2001,03). Sixteen land-use/land-cover, topography, and Normalized Difference Vegetation Index (NDVI) variables were used as predictors to build generalized additive models (GAMs). Both occurrence and abundance models showed a good predictive ability. Land use, altitude, and NDVI during spring previous to the arrival of hawks to wintering areas were good predictors of the distribution of Swainson's hawks in the Argentine pampas, but only land use and NDVI were entered into the model of abundance of the species in the region. The predictive cartography developed from the models allowed us to identify the current wintering area of Swainson's hawks in the Argentine pampas. The highest occurrence probability and relative abundances for the species were predicted for a broad area of south-eastern pampas that has been overlooked so far and where neither field research nor conservation efforts aiming to prevent massive mortalities has been established. [source] Effect of stinging nettle habitats on aphidophagous predators and parasitoids in wheat and green pea fields with special attention to the invader Harmonia axyridis Pallas (Coleoptera: Coccinellidae)ENTOMOLOGICAL SCIENCE, Issue 4 2009Ammar ALHMEDI Abstract The relative occurrence and seasonal abundance of aphids and their natural enemies were visually assessed between May and July 2005,2006 in four types of habitats located in Gembloux (Namur province, Belgium): green pea, wheat and stinging nettle either planted in or naturally growing in woodland adjacent to these crops. Results showed that: (i) Acyrthosiphon pisum Harris, Sitobion avenae F. and Microlophium carnosum Buckton were the most common aphid species, respectively, on green pea, wheat and stinging nettle either in or near field crops; (ii) stinging nettle and field crops shared several important aphidophagous insect species such as the ladybird Coccinella septempunctata L., hoverfly Episyrphus balteatus De Geer and braconid wasp Aphidius ervi Haliday; (iii) the shared beneficial species were typically recorded earlier on stinging nettles than on crops; and (iv) the spatial occurrence of the invasive ladybird Harmonia axyridis Pallas was distinctly associated with stinging nettles, particularly in 2005. Stinging nettles and field crops partially coincide in time, enabling the movement of natural enemies among them. These findings suggest that the presence of stinging nettles in landscapes seems to enhance the local density of aphidophagous insect communities necessary for aphid biocontrol in field crops. [source] Characterisation of aurone biosynthesis in Antirrhinum majusPHYSIOLOGIA PLANTARUM, Issue 4 2006Kevin M. Davies Aurones are bright yellow flavonoids produced in petals of a limited range of plant species, including Antirrhinum majus. The biosynthesis of aurones is thought to occur by the action of aureusidin synthase (AUS), and possibly aureusidin 7- O -glucosyltransferase (A7GT). The temporal and spatial occurrence of AUS and A7GT transcript was examined in wild-type A. majus and two mutant lines; sulfurea, which has increased aurone production in petals, and violacea, which has reduced aurone production. AUS and A7GT transcript abundance was similar in all three lines, increasing during flower development coincident with yellow coloration. The spatial pattern of AUS occurrence was also similar in all three lines, being spatially restricted to the inner epidermis of the face and throat of the lower petal. A new recessive line (CFR1011) with greatly reduced aurone production in all parts of the petal was identified by ethylmethanesulfonate mutagenesis of the homozygous recessive sulfurea line. Transcript abundance for AUS was not changed in the CFR1011 line compared with the wild-type line, and neither were any point mutations detected in the coding sequences for AUS or A7GT. Thus, the sulfurea, violacea and CFR1011 mutations do not seem to control aurone production through a change in transcript abundance of the predicted biosynthetic genes AUS or A7GT. To examine AUS gene regulation further, the putative AUS gene promoter region was isolated and compared with other A. majus flavonoid gene promoters. A number of conserved potential regulatory regions were identified, in particular a consensus site for the MYB-type transcription factors. [source] Human,environment interactions in residential areas susceptible to landsliding: the Flemish Ardennes case studyAREA, Issue 3 2010Miet Van Den Eeckhaut Studies on landslide susceptibility and landslide risk generally start from the assumption that mainly natural factors control the occurrence of landslides. The role of human activity is considered less important. We investigated the role of human,environment interactions in the Flemish Ardennes, Flanders' most landslide-susceptible region. The establishment of a detailed landslide inventory brought insight into the spatial occurrence of landslides and into the different landslide types and characteristics. A statistical model, i.e. logistic regression, allowed the significance of environmental factors controlling landslide occurrence to be determined, and a landslide susceptibility map to be produced. Being a residential area, however, the Flemish Ardennes is a region where humans play an active role with regard to landslide risk. Although the location of many archaeological sites in this area is known, almost no archaeological sites are found on landslide-susceptible hillslopes. This might indicate that in prehistorical and historical times humans were more familiar with local environmental characteristics and avoided unstable hillslopes. Comparison of topographic maps (1777,2001), on the contrary, indicate that over the last 250 years buildings and other infrastructures have been constructed on old landslides. Given that humans are living, working and driving on or close to unstable hillslopes, the landslide risk has therefore increased. The landslide inventory map and the landslide susceptibility map are important tools for landslide risk reduction. Here ,science meets policy', as both maps allow linking construction norms and other mitigation measures to hillslopes already affected by landslides and to susceptibility classes with very high, high and moderate landslide susceptibility. [source] | ||||||||||