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Prior research has demonstrated a strong association between the species of predators that co-occur with guppies and the evolution of guppy life histories. The evolution of these differences in life histories has been attributed to the higher mortality rates experienced by guppies in high-predation environments. Here, we evaluate whether there might be indirect effects of predation on the evolution of life-history patterns and whether there are environmental differences that are correlated with predation. To do so, we quantified features of the physical and chemical environment and the population biology of guppies from seven high- and low-predation localities. We found that high-predation environments tend to be larger streams with higher light levels and higher primary productivity, which should enhance food availability for guppies. We also found that guppy populations from high-predation environments have many more small individuals and fewer large individuals than those from low-predation environments, which is caused by their higher birth rates and death rates. Because of these differences in size distribution, guppies from high-predation environments have only one-fourth of the biomass per unit area, which should also enhance food availability for guppies in these localities. Guppies from high-predation sites allocate more resources to reproduction, grow faster, and attain larger asymptotic sizes, all of which are consistent with higher levels of resource availability. We conclude that guppies from high-predation environments experience higher levels of resource availability in part because of correlated differences in the environment (light levels, primary productivity) and in part as an indirect consequence of predation (death rates and biomass density). These differences in resource availability can, in turn, augment the effect of predator-induced mortality as factors that shape the evolution of guppy life-history patterns. We found no differences in the invertebrate communities from high- and low-predation localities, so we conclude that there do not appear to be multitrophic, indirect effects associated with these differences in predation.

The oxygen store/usage hypothesis suggests that larger animals are able to dive for longer and hence deeper because oxygen storage scales isometrically with body mass, whereas oxygen usage scales allometrically with an exponent <1 (typically 0.67-0.75). Previous tests of the allometry of diving tend to reject this hypothesis, but they are based on restricted data sets or invalid statistical analyses (which assume that every species provides independent information). Here we apply information-theoretic statistical methods that are phylogenetically informed to a large data set on diving variables for birds and mammals to describe the allometry of diving. Body mass is strongly related to all dive variables except dive:pause ratio. We demonstrate that many diving variables covary strongly with body mass and that they have allometric exponents close to 0.33. Thus, our results fail to falsify the oxygen store/usage hypothesis. The allometric relationships for most diving variables are statistically indistinguishable for birds and mammals, but birds tend to dive deeper than mammals of equivalent mass. The allometric relationships for all diving variables except mean dive duration are also statistically indistinguishable for all major taxonomic groups of divers within birds and mammals, with the exception of the procellariiforms, which, strictly speaking, are not true divers.

Conducting cost-benefit analyses of architectural attributes such as security has always been difficult, because the benefits are difficult to assess. Specialists usually make security decisions, but program managers are left wondering whether their investment in security is well spent. This paper summarizes the results of using a cost-benefit analysis method called SAEM to compare alternative security designs in a financial and accounting information system. The case study presented in this paper starts with a multi-attribute risk assessment that results in a prioritized list of risks. Security specialists estimate countermeasure benefits and how the organization's risks are reduced. Using SAEM, security design alternatives are compared with the organization's current selection of security technologies to see if a more costeffective solution is possible. The goal of using SAEM is to help information-system stakeholders decide whether their security investment is consistent with the expected risks.

The aim of this study was to investigate whether bovine faeces could replace rumen liquor collected from fistulated sheep in the determination of organic matter digestibility (OMD) of forages in vitro. The first experiment compared two inocula that had been prepared by mixing 83 and 333 g of cattle faeces with 1 litre of artificial saliva according to the first stage of the in vitro technique of Tilley and Terry (Journal of the British Grassland Society,18, 104–111, 1963). Inocula made from 333 g of faeces gave higher values of OMD than that prepared from 83 g of faeces and was used in subsequent studies. When a 48‐h acid pepsin digestion, the second stage of the Tilley and Terry (1963) technique, was included, the OMD values and the ease of filtering of undigested residues were increased. The second experiment compared digestibility determined with inocula produced from faeces with that produced from rumen liquor. The OMD of a ryegrass hay determined with an inoculum prepared from faeces was 0·468 compared with 0·528 when using an inoculum prepared from rumen liquor. The third experiment investigated the accuracy of estimating the OMD of eight contrasting forages determined using rumen liquor from three sheep (y) and faeces from two cows (x). All regressions were significant (P < 0·001) and had residual standard deviations (r.s.d.) of between ±0·019 and ±0·022. The final study compared faeces collected from cattle fed with either hay or concentrates. The OMD of forage was higher from the hay‐fed animals, but the r.s.d. values of the regressions were similar. It was concluded that cattle faeces shows potential as an alternative to rumen liquor collected from rumen‐fistulated sheep for use in the in vitro digestibility assay of forages.

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Freshly harvested Striga asiatica L. seeds will germinate in response to a stimulant only after the passage of time, an after‐ripening period, and exposure to moisture at a suitable temperature, a conditioning period. To investigate the role of seed moisture content in the regulation of the after‐ripening period, seeds were placed in chambers having specific relative humidity of 6%, 14%, 33%, 75% and 91% for 30, 60, 90 and 150 days. The seeds were then conditioned and germination percentage, response to tetrazolium and seed moisture contents were measured. Seeds at moisture contents less than 10% at the start of conditioning had germination of greater than 93%. Seeds at moisture contents over 10% at the start of conditioning could germinate between 60% and 3%, with germination decreasing as seed moisture content at the start of conditioning increased. The highest moisture content (17%) and lowest germination percentage (3%) occurred in seeds stored at 91% relative humidity for 150 days. There was a linear relationship of a high degree of correlation (0.997) between a positive tetrazolium test and germination capacity. Germination capacity of seeds could be changed from 90% to 3% by prolonged storage in water (dilute benomyl solution), causing `wet dormancy', then returned to 90% germination by returning to dry storage. Seed moisture content at the beginning of conditioning appears to control the responsiveness of the seeds to germination stimulants. The implications of these findings to the control of the parasite are discussed.