2000. Macroecology of a host-parasite relationship. -Ecography 23: 11 -20.The larvae of freshwater mussels are obligate ectoparasites on fishes while adults are sedentary and benthic. Dispersal of mussels is dependent on the movement of fish hosts, a regional process, but growth and reproduction should be governed by local processes. Thus, mussel assemblage attributes should be predictable from the regional distribution and abundance of fishes. At a broad spatial scale in the Red River drainage, USA, mussel species richness and fish species richness were positively associated; maximum mussel richness was limited by fish richness, but was variable beneath that constraint. Measured environmental variables and the associated local fish assemblages each significantly accounted for the regional variation in mussel assemblages. Furthermore, mussel assemblages showed strong spatial autocorrelation. Variation partitioning revealed that pure fish effects accounted for 15.4% of the variation in mussel assemblages; pure spatial and environmental effects accounted for 16.1% and 7.8%, respectively. Shared variation among fish, space and environmental variables totaled 40%. Of this shared variation, 36.8% was associated with the fish matrix. Thus, the variation in mussel assemblages that was associated with the distribution and abundance of fishes was substantial ( \ 50%), indicating that fish community structure is an important determinant of mussel community structure. Although animals commonly disperse plants and, thus, influence the structure of plant communities, our results show a strong macroecological association between two disparate animal groups with one strongly affecting the assemblage structure of the other.C. C. Vaughn (c6aughn@ou.edu),

There is a lack of evidence on regulatory effectiveness available to support policy makers with the selection of appropriate instruments to deliver better environmental regulation. We identify the types of evidence required to enable regulatory reform, characterize evidence gaps, and explore how these may be filled through future research. A typology of regulatory instruments is presented, and evidence of what has worked when and why is examined, drawing on international experience and recent cases from the United Kingdom (UK). Evidence of the capabilities of good environmental regulators for regulatory effectiveness is lacking, and it is proposed that ethnographic research that captures the nuances of regulatory practice will prove necessary to address this. This paper is of value to policy makers and regulators around the world considering the selection and deployment of the full range of environmental regulatory instruments to respond to environmental risks and in support of economic growth. It can inform the selection of suitable approaches and the design of institutions capable of delivering them. Copyright © 2012 John Wiley & Sons, Ltd and ERP Environment.

a b s t r a c tIntroducing hierarchy into structures has been credited with improving elastic properties and damage tolerance. Specifically, adding hierarchical sub-structures to honeycombs, which themselves have good-density specific elastic and energy-absorbing properties, has been proposed in the literature. An investigation of the elastic properties and structural hierarchy in honeycombs was undertaken, exploring the effects of adding hierarchy into a range of honeycombs, with hexagonal, triangular or square geometry super and sub-structure cells, via simulation using finite elements. Key parameters describing these geometries included the relative lengths of the sub-and super-structures, the fraction of mass shared between the sub-and super-structures, the co-ordination number of the honeycomb cells, the form and extent of functional grading, and the Poisson's ratio of the sub-structure. The introduction of a hierarchical sub-structure into a honeycomb, in most cases, has a deleterious effect upon the in-plane density specific elastic modulus, typically a reduction of 40 to 50% vs a conventional non-hierarchical version. More complex sub-structures, e.g. graded density, can recover values of density specific elastic modulus. With careful design of functionally graded unit cells it is possible to exceed, by up to 75%, the density specific modulus of conventional versions. A negative Poisson's ratio sub-structure also engenders substantial increases to the density modulus versus conventional honeycombs.

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This study re-analysed 14 semi-structured interviews with policy officials from the UK Department for Environment, Food and Rural Affairs (Defra) to explore the use of a variety of regulatory instruments and different levels of risk across 14 policy domains and 18 separately named risks. Interviews took place within a policy environment of a better regulation agenda and of broader regulatory reform. Of 619 (n) coded references to 5 categories of regulatory instrument, 'command and control' regulation (n = 257) and support mechanisms (n = 118) dominated the discussions, with a preference for 'command and control' cited in 8 of the policy domains. A framing analysis revealed officials' views on instrument effectiveness, including for sub-categories of the 5 key instruments. Views were mixed, though notably positive for economic instruments including taxation, fiscal instruments and information provision. An overlap analysis explored officials' mapping of public environmental risks to instrument types suited to their management. While officials frequently cite risk concepts generally within discussions, the extent of overlap for risks of specific significance was low across all risks. Only 'command and control' was mapped to risks of moderate significance in likelihood and impact severity. These results show that policy makers still prefer 'command and control' approaches when a certainty of outcome is sought and that alternative means are sought for lower risk situations. The detailed reasons for selection, including the mapping of certain instruments to specific risk characteristics, is still developing.