Despite the importance of consumers in structuring communities, and the widespread assumption that consumption is strongest at low latitudes, empirical tests for global scale patterns in the magnitude of consumer impacts are limited. In marine systems, the long tradition of experimentally excluding herbivores in their natural environments allows consumer impacts to be quantified on global scales using consistent methodology. We present a quantitative synthesis of 613 marine herbivore exclusion experiments to test the influence of consumer traits, producer traits and the environment on the strength of herbivore impacts on benthic producers. Across the globe, marine herbivores profoundly reduced producer abundance (by 68% on average), with strongest effects in rocky intertidal habitats and the weakest effects on habitats dominated by vascular plants. Unexpectedly, we found little or no influence of latitude or mean annual water temperature. Instead, herbivore impacts differed most consistently among producer taxonomic and morphological groups. Our results show that grazing impacts on plant abundance are better predicted by producer traits than by large-scale variation in habitat or mean temperature, and that there is a previously unrecognised degree of phylogenetic conservatism in producer susceptibility to consumption.

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Density, biomass and productivity of animals >0.5 mm were estimated in 4 shallow subtidal rocky reef habitats in temperate northeastern New Zealand. The main objective was to determine the relative contributions of mobile epifauna (0 5-10 mm) and megafauna (> 10 mm) to the flux of materials on the reef. The habitats surveyed were (1) Carpophyllum plumosuln var. capillifolium forest (Phaeophyceae: Fucales), (2) Ecklonia radiata forest (Phaeophyceae: Laminariales), (3) urchin barrens, and (4) articulated coralline algal turf flats. Epifauna comprised >99.5% of individuals in each habitat. Epifauna dominated biomass (>8ti':11) in the finely structured C~rpophyllum forest and turf flats, where they contributed > g ? % of total secondary product~vity. Although lower in the other 2 habitats, the epifauna1 contribution to total secondary product~vity was still -78":) on the scale of the entire reef. These results show that epifauna are major contributors to the flux of materials in rocky reef habitats, and should therefore be included in trophic models of these systems. Consumption by fish could only account for -26% of epifaunal product~on, with the fate of the remainder unknown. Estimated annual secondary productivity within the Carpophyllum torest and turf flats habltats (100 to 115 g AFDW in-' yr-') was hlgher than literature values for a range of soft sediment habitats, and was exceeded only by 2 other hard-bottom communities.

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The synthesis, characterization, and exploratory chemistry of two classes of alkene-platinum-silyl complexes, which have been postulated as hydrosilation intermediates, are described in this report. The unique dimeric complexes 1, [R(3)Si(mu-Cl)(eta(2)-COD)Pt](2) [R(3)Si = Et(3)Si, MeCl(2)Si, Me(2)ClSi, "(EtO)(3)Si", PhMe(2)Si, and (Me(3)SiO)Me(2)Si; COD = cycloocta-1,5-diene], and the bis-silyl complexes 2, (eta(4)-COD)Pt(SiR(3))(2) (R(3)Si = Cl(3)Si, MeCl(2)Si, Me(2)ClSi, and PhMe(2)Si), are formed from the sequential reaction of 2 and 4 equiv of the corresponding hydrosilanes, respectively, with Pt(COD)Cl(2) in the presence of a small excess of COD. Complexes 1 are stable for many days in solution at room temperature but decompose via slow elimination of chlorosilane. Some of the bis-silyl compounds 2 are stable for extended periods under inert atmosphere and especially below 0 degrees C, either in the solid state or in solution (in the presence of a small excess of free COD). Complexes 2 display catalytic activity as discrete, molecular, and mononuclear species for hydrosilation and isomerization reactions. Compound 2c (R(3)Si = MeCl(2)Si) was fully characterized via multinuclear NMR spectroscopy and X-ray crystal structure analysis. The facile H-transfer rather than Si-transfer to bound COD provides experimental support for the sequence of insertive steps in the Chalk-Harrod catalytic cycle, at least for Pt-catalyzed hydrosilation.