Changes in the Lepidoptera of Monks Wood NNR (1974-2003)

Introduction Monks Wood has been noted for the richness of its Lepidoptera, particularly butterflies, sinceat least the middle of the 19th century. In 1828 the black hairstreak was discovered for the first time in Britain in Monks Wood. A total of 48 butterfly species have been recorded in the Monks Wood area but today only 30 species (including two non-resident migrants) can be found there. Most of the losses had occurred by the time the Monks Wood book (Steele & Welch 1973) was published (Table 1). Less is known historically about the moth fauna. Steele & Welch (1973) listed some 129 microlepidoptera and 332 macrolepidoptera (hereafter referred to as macro-moths). These records came from variety of sources collated from the many collectors who had visited Monks Wood for well over a century. The list includes some species that have not been recorded in recent decades, some of which are almost certainly extinct in the wood (Table 2). The number of microlepidoptera recorded in the wood has greatly increased but no current list has been compiled. The current list of macro-moths stands at 460 species. Monks Wood has contributed to national recording schemes for both butterflies (Butterfly Monitoring Scheme – BMS) and moths (Rothamsted Insect Survey) for three decades and it is these standardised observations that allow an examination of change within Monks Wood and a comparison with national statistics. An earlier study by Pollard and others (1998), using these data, concluded that an increase in coarse grasses had benefited Lepidoptera feeding on them at the expense of those feeding on finer grasses. Several possible causes included ride management practices, the colonisation of the wood by muntjac, and an increase in atmospheric nitrogen deposition. In the current study we examine both the butterfly transect data and the Rothamsted Insect Survey (light trap) moth data for changes over the last 30 year

A multispecies perspective on ecological impacts of climatic forcing

P>1. In the prevailing context of concerns over climate change and its potential impacts on ecosystems, evaluating ecological consequences of climatic forcing has become a critical issue. 2. Historical data on the abundance of organisms have been extensively used to characterize the ecological effects of climatic forcing through specific weather and/or climatic variables, with most of the studies confined to single population models. 3. However, population responses to environmental fluctuations typically depend upon positive and negative feedbacks induced by interactions with other species. It is therefore important to integrate the insights gained from single population approaches into a multispecies perspective. 4. Here we combine the hierarchical Bayesian modelling approach with the state-space formulation to extend the scope of previously proposed models of population dynamics under climatic forcing to multi-species systems. 5. We use our model to analyse long-term macro-moth (Lepidoptera) community data from the Rothamsted Insect Survey network in the UK, using winter rainfall and winter temperature as environmental covariates. 6. The effects of the two weather variables were consistent across species, being negative for winter rainfall and positive for winter temperature. The two weather variables jointly explained 15-40% of the total environmental variation affecting the dynamics of individual species, and could explain up to 90% of covariances in species dynamics. 7. The contribution of interspecific interactions to community-level variation was found to be weak compared to the contributions of environmental forcing and intraspecific interactions

Melanic frequencies in three species of moths in post industrial Britain

Changing patterns of morph frequency in three moth species (Biston betularia, Odontoptera bidentata and Apocheima pilosaria) have been investigated using data from the Rothamsted Insect Survey. All three exhibited industrial melanism during the period of high atmospheric pollution in Britain. Three historical and habitat types are compared, the old industrial north of England, rural Scotland, Wales and South-West England, and a southern English intermediate region of high human population density but generally low industrialization. Between 1974 and 1999 the carbonaria morph of B. betularia declined in frequency in the industrial region and is nearly absent from rural areas. It is the form which most closely tracks atmospheric change. It is shown that the insularia forms of B. betularia and the melanic morphs in the other two species have decreased in the industrial region, commencing later than carbonaria, but have maintained their presence and possibly reached equilibrium elsewhere. They may be non-industrial polymorphisms. B. betularia is rarer than the other species and all three species are at lower densities in industrial than in non-industrial regions

Long-term changes in the abundance of flying insects

For the first time, long-term changes in total aerial insect biomass have been estimated for a wide area of Southern Britain. Various indices of biomass were created for standardised samples from four of the Rothamsted Insect Survey 12.2 m tall suction traps for the 30 years from 1973 to 2002. There was a significant decline in total biomass at Hereford but not at three other sites: Rothamsted, Starcross and Wye. For the Hereford samples, many insects were identified at least to order level, some to family or species level. These samples were then used to investigate the taxa involved in the decline in biomass at Hereford. The Hereford samples were dominated by large Diptera, particularly Dilophus febrilis, which showed a significant decline in abundance. Changes in agricultural practice that could have contributed to the observed declines are discussed, as are potential implications for farmland birds, with suggestions for further work to investigate both cause and effect