Criminal directionality and the structure of urban form

Spatial criminology has three interrelated elements: place, distance, and direction. Though directionality has had theoretical support for many years, very few empirical verifications of this component of crime have emerged. In this article, we investigate the strength of directionality by comparing a simulated randomized dataset and a large incident-based dataset of repeat offenders. We find strong evidence for a strong presence of directionality in criminal spatial decision-making. This aspect of the spatiality of crime must be considered in any attempts to understand the aetiology of crime.     

Ecological Status of a Margaritifera margaritifera (Linnaeus, 1758) Population at the Southern Edge of its Distribution (River Paiva, Portugal)

An important population of the critically endangered pearl mussel Margaritifera margaritifera (Linnaeus, 1758) was surveyed at the edge of its southern distribution (River Paiva, Portugal). Although an earlier study suggested that this population had a very low number of individuals (<500), a narrow distribution, and was mainly comprised by old specimens our data contradict these findings. Our assessment estimated a population with probably more than 5,000 individuals distributed across 80 km of the river length. From the 32 sites surveyed, 19 contained M. margaritifera with higher abundances verified in the middle and upper parts of the river (a maximum of 78 ind. per 100 m of river stretch was recorded). The pearl mussels showed a clear preference for areas near the banks, in shallow water, sandier and gravel sediments, and a high degree of riparian vegetation cover. The population structure was skewed with a very high percentage of large (and old) animals but 3.7 % of the individuals collected were juveniles (<60 mm in length); therefore, this population can be considered functional. Environmental characterization indicated that this river is still in excellent or good condition although some areas showed deterioration due to discharge of domestic effluents. The main conservation requirements of M. margaritifera in the River Paiva include maintaining the water quality (and if possible stopping the discharge of domestic effluents), increasing riparian vegetation cover, removing several weirs to increase connectivity, and increasing trout density.     

Weapons or mating signals? Claw shape and mate choice in a fiddler crab

Males often possess traits, such as horns, claws, and tusks, which are used during male–male combat. Studies suggest that selection has fine tuned these weapons to improve their effectiveness and that the shape of these weapons provides cues for males to assess the strength of rivals. Similarly, females might also assess a male’s weaponry to determine his value as a mate. The largest weapon relative to body size is the major claw of male fiddler crabs (genus: Uca). Males use their claws both as a weapon and as a courtship signal, waving it to attract females. We used robotic crabs in two-choice experiments to test female mating preferences based on male claw shape in Uca mjoebergi. First, females did not prefer conspecific claws over any of three alternatively shaped stimuli matched for color and for the rate and pattern of waving. The alternative stimuli were two different heterospecific claws and a plain rectangular shape. Second, females significantly preferred the alternative stimuli when they were presented at a faster wave rate. We conclude that claw shape in U. mjoebergi has not evolved under sexual selection imposed by female mating preferences and is more likely to have evolved under selection for effectiveness during male–male competition.     

Fitness consequences of choosy oviposition for a time-limited butterfly

For the majority of insects, a female's choice of oviposition site(s) greatly influences both the success of individual offspring and her own total fitness. Theory predicts that females most strongly limited by egg number will employ greater oviposition site discrimination than those predominately subject to time limitation. The reproductive success of the butterfly Pieris virginiensis at our Connecticut, USA, field site is strongly time constrained on two fronts. First, during their three-week flight season, only 60% of days and 28% of daytime hours were suitable for flight. Second, larval survival is impacted by the rapid senescence of their spring ephemeral host plant Dentaria diphylla, with eggs laid during the first half of the flight season having approximately three times the survival chance of those laid later. Yet, on average, females choose to oviposit on only half the plants they closely inspect and fly over most ramets without any inspection. Our experiments demonstrate that the preferred host ramets confer an approximate two-fold survival advantage. Females are not choosing plants that senesce later, despite the advantage that such plants would confer. We use empirical data on female behavior and larval performance to parameterize a simulation model. Model results suggest that, despite the notable time limitation in this system, the observed level of female oviposition site preference not only increases individual larval survival, but also total female fitness. Low egg loads in this species may contribute to selection for strong host plant discrimination.     

Effects of equilibration time on photoreactivity of the pollutant DDE sorbed on natural sediments

Photolysis of the hydrophobic pollutant 1,1-$\text{bis}$($\text{p}$-chlorophenyl)-2,2-dichloroethylene (DDE) was studied in aqueous suspensions of three well-characterized sediments. Results of the study can be described by equations that are based on a kinetic model that takes into account sorption kinetics. Analysis of the kinetic data using this model indicates that the sorbed DDE is, at equilibrium, about half in reactive sites and half in sites where the DDE is unreactive.     

Genetic and Demographic Threats to the Black Rhinoceros Population in the Ngorongoro Crater

A resident population of 13 black rhinoceros ( Diceros bicornis ) persist in Ngorongoro Crater, Tanzania. The effective population size ( N _e ) may be as few as 5 animals. Projected growth for this population suggests that the effective population size will remain small for the near future, threatening this Iocal population with extinction due to the stochastic factors associated with small population size. A summary of historic and recent demographic data for this population reveals a population crash during the period of heavy poaching that affected this species throughout its range. Although poaching of this species has been brought under control the population remains small. These data and models of projected population growth argue for consideration of more-intensive management within the framework of the small population paradigm. This case is an example of applied conservation resulting from this paradigm used in conjunction with rather than competing with the declining population paradigm. We identify additional monitoring, particularly of density-dependent behaviors, that will be necessary for designing a successful management program. Finally, the use of molecular markers for developing an accurate pedigree for this population is suggested in order to maintain a genetically healthy population. These strategies have broad applicability to black rhinoceros conservation throughout Africa.     

Comparison of photochemical behavior of various humic substances in water: I. Sunlight induced reactions of aquatic pollutants photosensitized by humic substances

Humic substances are shown to photosensitize transformations of several types of synthethic chemicals that do not photoreact when exposed to sunlight in distilled water. In most cases, photoproducts were the same in colored natural waters and in solutions of soil-derived humic substances, including those obtained commercially. Kinetic studies in sunlight indicated that the efficiencies of the reactions photosensitized by humic substances of various origins were the same within a factor of 2.     

Specific detection of organotin compounds with a recombinant luminescent bacteria

Organotin compounds are widely used as biocides in marine and terrestrial environments. Several currently used techniques allow either the measurement of the chemicals or their effects on living organisms. Our current research focuses on the development of a complementary method based on a bacterial bioluminescence-based bioassay for the specific detection of organotin compounds. The performance of the bioassay was assessed. The Escherichia coli bacterial strain used in this study is specific for TBT and DBT (with Cl, Br or I as the halogen group) with the central tin atom important for light production. The assay is conducted after overnight culture of the bacterial strain, followed by 60 min of contact time with the organotin compound for significant light production. The detection limits were found to be 0.08 microM for TBT (26 microgl(-1)) and 0.0001 microM for DBT (0.03 microgl(-1)) with a linear range of one logarithm. The repeatability of the bioassay is 8% and the reproducibility for TBT and DBT was approximately 14%. Lyophilization of the strains did not significantly modify the detection limit as well as the range of detection. Applications of the bioassay to environmental samples are discussed.     

Spatial and temporal trends in surface water and sediment contamination in the Laurentian Great Lakes

Data from recent sediment and surface water surveys have been collated and mapped to illustrate the spatial distribution of contaminants across the entire Great Lakes basin. Information from historical surveys, together with data from surface water monitoring programs in three major connecting channels, has also been collated in order to evaluate temporal trends. In general, Lakes Superior and Michigan exhibited the lowest levels of sediment contamination while Lake Ontario had the highest. Contaminants such as gamma-HCH (lindane) and dieldrin were ubiquitous in surface waters across the entire basin, which was indicative of atmospheric sources. The distribution of other compounds including hexachlorobenzene, octachlorostyrene and mirex indicated the presence of local sources within the watersheds of the connecting channels. Surficial sediment contamination was found to have decreased markedly since the late 1960s and 1970s. Similarly, surface water contamination decreased over the period 1986-1997 with concentrations of dieldrin, hexachlorobenzene, octachlorostyrene and mirex reduced by over 50%. However, the spatial distributions of both sediment and surface water contamination indicate that further effort is warranted in reducing local sources of contaminants, particularly in Lake Ontario.