A simple habitat assessment score (HAS) was designed to assess habitat complexity across several different shallow tropical marine habitats including sandy patches, algal beds, seagrass beds and reefs. It measured rugosity, variety of growth forms, height, refuge size categories, percentage live cover and percentage hard substratum. Multiple regression models using HAS variables as predictors accounted for 71 and 22% of the variation in observed species richness and total fish abundance respectively. The two most important predictors of observed species richness were rugosity and variety of growth forms, while height was the most important predictor of total fish abundance. The HAS method worked consistently across a variety of habitat types and the complexity map closely mirrored the map of observed species richness, reflecting the patchy habitat mosaic of shallow tropical marine areas. Stations at the mouth of an enclosed lagoon, however, had a higher number of species than might have been expected judging from the habitat complexity scores. It is possible that this was linked to the preferential settling of pelagic fish larvae in this area as tidal water exchanges between the bay and the reef were funnelled through one small gap. This study highlights the need for fish biodiversity studies to take habitat complexity into account. # 2005 The Fisheries Society of the British Isles

Sets of artificial reefs were replicated in 5 bays off Tortola in the British Virgin Islands to investigate the effects of habitat complexity on fish assemblages. Increasing percentage hard substrate and the number of small reef holes increased fish abundance on reefs. The observed number of species (S obs ) occurring on each reef increased with increasing rugosity, variety of growth forms, percentage hard substrate, and variety of refuge hole sizes. A rarefied or abundance-corrected species richness measure (S rare ) was calculated to take the varying fish abundances into account. After this correction, rugosity was the only variable that significantly increased fish species-richness. Experimental reefs of different height (20 and 60 cm) did not have significantly different fish abundance or species richness. The presence of long-spined sea urchins Diadema antillarum increased S obs and total fish abundance on artificial rock-reefs and in seagrass beds, but the effect was most pronounced in seagrass beds where shelter was a strongly limiting factor. These results indicate that complex habitats or animals such as D. antillarum that provide shelter to fish are essential for maintaining fish biodiversity at local scales. The most important aspects of complexity are rugosity, hard substrate and small refuge holes. Artificial reefs may be used to mitigate habitat damage in impacted areas, and if management objectives are to increase local fish abundance and species richness, the reefs should provide a stable substrate where this is unavailable, have a rugose surface with many small refuge holes, and have a variety of growth forms.

The diversity of beetle assemblages in different habitat types (primary forest, logged forest, acacia plantation and oil palm plantation) in Sabah, Malaysia was investigated using three different methods based on habitat levels (Winkler sampling, flight-interception-trapping and mist-blowing). The overall diversity was extremely high, with 1711 species recorded from only 8028 individuals and 81 families (115 family and subfamily groups). Different degrees of environmental changes had varying effects on the beetle species richness and abundance, with oil palm plantation assemblage being most severely affected, followed by acacia plantation and then logged forest. A few species became numerically dominant in the oil palm plantation. In terms of beetle species composition, the acacia fauna showed much similarity with the logged forest fauna, and the oil palm fauna was very different from the rest. The effects of environmental variables (number of plant species, sapling and tree densities, amount of leaf litter, ground cover, canopy cover, soil pH and compaction) on the beetle assemblage were also investigated. Leaf litter correlated with species richness, abundance and composition of subterranean beetles. Plant species richness, tree and sapling densities correlated with species richness, abundance and composition of understorey beetles while ground cover correlated only with the species richness and abundance of these beetles. Canopy cover correlated only with arboreal beetles. In trophic structure, predators represented more than 40% of the species and individuals. Environmental changes affected the trophic structure with proportionally more herbivores (abundance) but fewer predators (species richness and abundance) in the oil palm plantation. Biodiversity, conservation and practical aspects of pest management were also highlighted in this study.

The diversity of macromoths in the various fast-growing exotic tree plantations and natural secondary forest in Brumas, Sabah, Malaysia was assessed by means of an annual cycle of light-trap samples. The moth diversity in the forest plantations, viz. Acacia mangium, Gmelina arborea, Paraserianthes (=Albizia) falcataria, Pinus caribaea, and in particular Eucalyptus deglupta, was unexpectedly high. Eucalyptus deglupta showed moth diversity as high as that in the natural secondary forest, a finding attributed to the fact that the E. deglupta plantation had a very diverse understorey both in terms of plant species (secondary regrowth species) and architecture, and thus supported a more diverse moth fauna. Subsidiary samples showed that primary natural forest in the neighbouring Danum Valley does not show higher moth diversity compared to the disturbed forest habitats in Brumas, though moth diversity at Danum is lower than that recorded in other Bornean primary forests. The value of plantation forests for conservation of invertebrate diversity is discussed, together with the implications for plantation management strategy.

Pitfall trapping was carried out in a field of winter wheat in the Vale of York to determine the levels of abundance of adult carabid and staphylinid beetles, (which formed the bulk of the natural predator complex) in the field. A point quadrat survey was carried out at the same time to assess the vegetation cover round each trap. Predation pressure by the beetles in the field was monitored using fruit fly (Drosophila) pupae as artificial prey. These artificial prey were attached to small cards inserted in the field adjacent to the pitfall traps.The numbers of beetles caught were found to be directly related to the frequency and density of Poa annua L. (annual meadow grass) the only abundant non-crop plant present at the time. More beetles were caught in areas where Poa was abundant than where Poa was scarce. This was probably related to the more suitable environmental factors offered by these of the wheat itself was found to be unrelated to captures.The number of fruit fly pupae taken was shown to be related to the numbers of carabid and staphylinid beetles present, and also to the type of vegetation occuring around each card.The implication of these results for the effects of predation on potential pest-outbreaks in the crop are discussed.