Egg cannibalism by sticklebacks: spite or selfishness?

Summary Although it is generally agreed that humans can be spiteful, there are few if any, unambiguous examples of spite by non-human animals. Data are presented suggesting that female threespine sticklebacks show spiteful behaviour. In the field, they seek out conspecific eggs to attack while largely ignoring those of a closely-related sympatric species, the blackspotted stickleback. This occurs despite the fact that the latter's nests are more abundant and less well protected. In the laboratory, female threespine sticklebacks attack the eggs of conspecifics more than those of blackspotted sticklebacks, those of sympatric conspecific females more than those of allopatric females, and older eggs more than younger ones. Because there was no evidence of greater energetic or nutritional advantages from eating conspecific rather than heterospecific eggs, or older eggs rather than younger ones, threespine sticklebacks may be spiteful. Alternative proximate and evolutionary hypotheses to explain this discriminant egg-eating are discussed.     

Ecotypic differentiation in light-related traits of the kelp Laminaria saccharina

Light-related traits were compared for Laminaria saccharina Lamour. collected from three habitats in Maine and New York, USA, with different ambient light regimes. Light-level, expressed as a proportion of surface irradiance (I₀), ranged from 0.04 to 0.32 I₀ in the shallow habitat, but rarely exceeded 0.04 I₀ in the deep and turbid habitats. Juvenile sporophytes collected from each habitat in April, 1985, were grown at four acclimation light-levels (0.065, 0.12, 0.26, and 0.54 I₀) in a common-garden, laboratory experiment. Photosynthesis vs irradiance (PI) parameters, light-harvesting characteristics, and rates of carbon-assimilation and growth were determined for each group of plants. The results indicated that ecotypic differentiation had occurred among the three kelp populations. Photosynthetic capacity (P_max) and photosynthetic efficiency () were generally highest for plants from the turbid habitat, lowest for deep plants, and intermediate for shallow plants. These differences were largely attributable to variations in light-harvesting characteristics. The nature and magnitude of photoacclimation responses also differed among populations. Population differences in photosynthetic parameters resulted in different rates of C-assimilation and growth by plants from shallow, deep, and turbid habitats. Predictions of in situ growth rates indicated that the severity of light-limitation and, therefore, the adaptive significance of efficient light-utilization vary among the three populations. It is concluded that ecotypic differentiation in light-related traits is important to the broad environmetal range of L. saccharina.     

An Inverse Gaussian distribution of tree frequencies based on tree size

Forest stand management often depends on data from a single fixed area inventory plot located at random in a forest stand. The plot provides detailed information about tree size distribution but not about per unit area tree frequency distribution unless one assumes a Poisson (POI) distribution. The POI assumption ignores any relationship between a tree's size and its demand for growing space. This study argues for the Inverse Gaussian (IG) distribution as a more realistic model. Maximum likelihood estimates of the IG parameters are obtained from a transformation of tree size data (diameter) to proxies of tree counts. Data from two stands indicated that an IG model was better at predicting the tree frequency distribution than a POI model.     

Joint versus separate estimation of state and change in category frequencies from repeat stratified two-phase sampling with a fallible classifier

Joint maximum likelihood estimates (JML) of category frequencies and change from repeat stratified two-phase samplingsurveys with a fallible classifier are often seriously biased andhave large root mean square errors when they are obtained for small populations (<5000) with three or more categories and amoderate to small phase II sample size (<1000). JML estimates of state also depend on antecedent or posterior data, a recipe for inconsistency. In these situations, a separate maximum likelihood estimation (SML) of category frequenciesat each survey date appears preferable. SML estimates of net change are obtained as the difference in states. SML standard errors of change are obtained via an estimate of the temporal correlation and variances of state. A bivariate binarylogistic model of change provided the estimate of temporal correlation. SML generally outperformed JMLsignificantly in terms of bias and root mean square errors in eight case studies.     

Nitrate leaching in agriculture to upper groundwater in the sandy regions of the Netherlands during the 1992–1995 period

The Dutch National Monitoring Programme for Effectiveness of the Minerals Policy (LMM) was initiated to allow detection of a statutory reduction in nitrate leaching caused by a decreasing N load. The starting point, or baseline, was taken as the nitrate concentration of the upper metre of groundwater sampled on 99 farms in the 1992–1995 period in the sandy areas of the Netherlands, where predominantly grass and maize grow. We found here that a reduction in nitrate leaching of more than 20% in future would almost certainly be detected with the LMM. Detecting downward trends due to decreasing N load will require nitrate concentrations to also be related to soil drainage, precipitation excess leading to groundwater recharge and to location. Furthermore, we found that about 16% of the N load in the Dutch sandy regions was being leached to the upper metre of groundwater in the 1992–1995 period. The critical N load in approximately 1990 for exceeding the EC limit value for nitrate, NO₃, (50 mg L^–1) in the upper metre of groundwater for the mean situation for grassland, maize and arable land in the sandy area was found to be 210 kg ha^–1 a^–1. Because manure management has been altered, the critical load found will be lower than the current critical load .     

Regulatory risk control through mandatory occupational safety and health (OSH) certification and testing regimes (CTRs)

Governments make increasing use of private certification and testing infrastructures as an alternative for traditional regulatory arrangements in several areas including occupational safety and health (OSH).This research, commissioned by the Dutch Inspectorate for Work and Income (IWI), concerns an analysis of risk control of four certification and testing regimes (CTRs) in the Netherlands, three mandatory regimes and one non-mandatory regime. The aim was to create a better understanding of problems that may arise in the risk control through such regimes and to identify critical processes and factors that can affect the risk control process.The results of this research are reported in two papers in this special issue (see also Zwetsloot et al., this issue). This one presents an analysis of the risk control at the regulatory level, and its associated critical factors and processes. These critical factors are clustered in four essential processes: the regulatory choice for a CTR, the definition of requirements for the auditing or inspection regime, the certification and testing processes as such, and the processes needed for the self-correcting or learning capability of the CTR. Jointly, these factors and processes form a framework for both the design and the evaluation of such regimes. The case studies clearly demonstrate that these critical factors may undermine the effectiveness of such regulatory practices. We propose that a further development of our framework should be used in the (re)design process for proposed and existing CTRs, and in the process of independent evaluation of such regimes.