Laboratory studies on the aggregation of feeding Dysdercus intermedius Distant (Heteroptera, Pyrrhocoridae)

RESP-540

Assessing Potential Impacts on Biodiversity using Critical Loads.

In many countries there has been much concern over maintaining biodiversity in natural ecosystems in the face of pressures such as changing land use and pollution. The 1992 UN Convention on Biodiversity calls upon signatories to develop national strategies for the conservation and sustainable use of biodiversity. In the UK, the potential impacts of sulphur and nitrogen deposition at the national level are being assessed using national critical loads and modelled deposition maps, together with available information on the occurrence of habitats and plant species. This simple approach gives an indication of the areas where atmospheric deposition may have impacts on biodiversity. The results of the analyses are presented and the strengths and weaknesses of the methods used are discussed. This first approach to considering the effects on biodiversity shows the importance of including the effects of atmospheric deposition in any biodiversity action plan. It also highlights those areas where more or improved information is required for the national strategy. With the modelled deposition data available, it would seem that reduced impacts are to be expected by 2010. However, higher resolution deposition data, better estimates of ammonium deposition, consideration of temporal aspects and the dynamics of change, and the use of higher resolution biological data sets are likely to suggest greater impacts than current predictions

Distribution pattern of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) on choy-sum plants

The distribution of all life-stages of Plutella xylostella (L.) on Choy-sum plants (Brassica rapa var. Spinach mustard) was investigated. The adults had a random distribution (P > 0.05), while the immature stages had a negative binomial (aggregated) distribution (P > 0.05). The adults and eggs were found mainly on the upper surface (P < 0.001) while the larvae (except the first instar) and pupae on the lower leaf surface (P < 0.001). The first instars were usually in the mines of leaves hollowed out by their feeding activities. The adults (P < 0.05), eggs (P < 0.001) and larvae (P < 0.05) were recorded mainly on the fully-opened leaves of intermediate age while the pupae (P < 0.01) on the oldest (also lowest) leaves. The larvae after hatching from eggs tended to clump together although they later dispersed as they grow, only to aggregate again during pupation

Elevated carbon dioxide affects leaf-miner performance and plant growth in docks (Rumex spp.).

Exposure of R. crispus and R. obtusifolius to elevated CO2 (600 ppm) resulted in an increased C:N ratio of leaf tissue and greater leaf areas. Larvae of P. nigritarsis mining leaves of R. obtusifolius during exposure produced significantly bigger mines in elevated than in ambient (350 ppm) conditions. There were no significant treatment effects on pupal weight although in both host species mean weight was greater in ambient than in elevated conditions. These results are consistent with the hypothesis that insect herbivores compensate for increased C:N ratios by increased food consumption. This response by herbivores may partially offset predicted increases in plant biomass in a future high CO2 environment