Simon R. Leather

Unravelling the evolution of autumn colours: an interdisciplinary approach

Leaf colour change is commonly observed in temperate deciduous forests in autumn. This is not simply a side effect of leaf senescence, and, in the past decade, several hypotheses have emerged to explain the evolution of autumn colours. Yet a lack of crosstalk between plant physiologists and evolutionary ecologists has resulted in slow progress, and so the adaptive value of this colour change remains a mystery. Here we provide an interdisciplinary summary of the current body of knowledge on autumn colours, and discuss unresolved issues and future avenues of research that might help reveal the evolutionary meaning of this spectacle of nature.

The biology and ecology of the large pine weevil, Hylobius abietis (Coleoptera: Curculionidae): a problem of dispersal?

The biology and pest status of Hylobius abietis Linnaeus in Europe are critically reviewed. New data are presented and the relationships between the weevil and its host plants considered. In Europe, H. abietis is the major pest of establishment forestry causing millions of ECUs of damage annually and perpetuating the addition of insecticide residues to sensitive habitats. Predator and parasitoid complexes in Britain and Europe are compared and contrasted. The lack of knowledge of the processes involved in adult dispersal and longevity are highlighted as major areas of concern. The biology and behaviour of the adult and larval stages are reviewed and new data presented. The feeding preferences of the adult weevils are considered and the possibility of using deterrents as a pest management strategy discussed. The development of risk assessment and forecasting tools aimed at more effective deployment of pest-management options are discussed. Risk criteria have their origins in important ecological relationships which require new understanding, but the prospects for determining high-risk forest sites are promising. The options for biological control are evaluated, in particular the use of mycopesticides and increased larval predation. It is concluded that much more research into the biology and ecology of H. abietis is required before a successful Integrated Pest Management (IPM) programme can be initiated.

Insect sampling in forest ecosystems

Contributors. Methods in Ecology series. Preface. 1 Sampling theory and practice: Simon R. Leather & Allan D. Watt. 2 Sampling insects from roots: Alan C. Gange. 3 Pitfall trapping in ecological studies: B.A. Woodcock. 4 Sampling methods for forest understorey vegetation: Claire M.P. Ozanne. 5 Sampling insects from trees: shoots, stems, and trunks: Martin R. Speight. 6 Insects in flight: Mark Young. 7 Techniques and methods for sampling canopy insects: Claire M.P. Ozanne. 8 Sampling methods for water--filled tree holes and their artificial analogues: S.P. Yanoviak & O.M. Fincke. 9 Sampling devices and sampling design for aquatic insects: Leon Blaustein & Matthew Spencer. 10 Methods for sampling termites: David T. Jones, Robert H.J. Verkerk & Paul Eggleton. 11 Parasitoids and predators: Nick Mills. Index

Factors determining the pest status of the bird cherry-oat aphid, Rhopalo-siphum padi (L.) (Hemiptera: Aphididae), in Europe: a study and review

The biology and pest status of Rhopalosiphum padi (L.) in Europe are critically reviewed. New data are presented and the temporal occurrence of the aphid and its host-plants considered. In Britain, R. padi is a pest mainly because of its ability to transmit virus diseases, in particular barley yellow dwarf virus. In other European countries, especially in Scandinavia, R. padi is a pest in its own right. Predator and parasite complexes in Britain and Finland are compared and contrasted. The occurrence of R. padi as a pest of cereals in Europe is compared with that of Sitobion avenae (F.) and Metopolophium dirhodum (Walker). It is postulated that the great abundance of the primary host of R. padi , bird cherry ( Prunus padus ), and the spring planting of cereals in colder climates such as in Finland are major factors contributing to the differences in pest status of this aphid between Britain and in Scandinavia.

Aphid growth and reproductive rates

Aphid size, although generally a good indicator of fecundity is not a good indicator of aphid performance over a wide range of conditions. In general, the greater the mean relative growth rate (MRGR) of apterous morphs of Rhopalosiphum padi (L.), the greater their fecundity. Intrinsic rate of increase (rm) is even more closely correlated with mean relative growth rate than fecundity.

INSECT SPECIES RICHNESS OF THE BRITISH ROSACEAE: THE IMPORTANCE OF HOST RANGE, PLANT ARCHITECTURE, AGE OF ESTABLISHMENT, TAXONOMIC ISOLATION AND SPECIES-AREA RELATIONSHIPS

SUMMARY (1) The number of species of Lepidoptera, Hymenoptera, Homoptera and Diptera feeding on British Rosaceae generally increases with the size of the geographic range of the host species, and with the complexity of the hosts morphology. (2) Within the Rosaceae, trees support more insect species than shrubs which in turn support more insect species than herbs. In addition, trees have more insect species within each insect guild and taxonomic grouping associated with them than shrubs, which in turn have more than herbs. (3) Although shrubs and herbs begin to accumulate insect species at a lower level of abundance than trees, trees accrue species at almost twice the rate of herbs and shrubs. The species-accrual rate for different guilds of insects (chewing, sucking and gall-forming) and for the four taxa of insects considered (Lepidoptera, Hymenoptera, Diptera and Homoptera) is greatest on trees except in the case of gall-forming insects and Diptera, where the rate is similar for trees, shrubs and herbs. (4) The older the plants history of establishment, based on the number of Quaternary records, the more insect species that are associated with it. Also, more recent less widespread plants have a greater polyphagous insect fauna than older more widespread plants. (5) Various analyses enabled 83%, 83% and 45% of the variation in insect species richness between trees, shrubs and herbs to be accounted for, respectively. The low variation accounted for in the case of the herbs may be the result of the poor quality of insect records for this group of plants. (6) Within given genera of plants, increases in geographical range and plant complexity are associated with an increase in the number of insects feeding upon them. When each genus within the Rosaceae was considered as a separate entity a similar pattern was seen. (7) Of the six plant genera with at least three members (Prunus, Sorbus, Rubus, Rosa, Cotoneaster, and Potentilla), Prunus has the most insect species associated with it and

Oviposition preferences in relation to larval growth rates and survival in the pine beauty moth, Panolis flammea

Abstract. 1. Adult female pine beauty moths, Panolis flammea (D & S), when given a choice of whole plants or needle pairs of four provenances of Lodgepole pine, Pinus contorta (Douglas), laid most eggs on that provenance on which the larvae attained their greatest growth rates.

The potential for manipulating crop–pest–natural enemy interactions for improved insect pest management

This review identifies key ways in which manipulations of the crop environment based on detailed understanding of tritrophic interactions can contribute to improvements in the control of insect pests. Such approaches are likely to be of particular benefit against those pests, notably certain species of Lepidoptera and aphid, which are difficult to control with insecticides because of insecticide resistance or suppression of natural enemies. Particular attention is given to the compatibility (or otherwise) of partial plant resistance and biological control, citing examples which support contrasting tritrophic theories. Other areas considered and supported with examples include the use or effects of allelochemicals, refugia, intercropping, crop backgrounds, fertilization regimes, parasitoid conditioning (by host plants) and transgenic crops. Examples of manipulations involving use of selective insecticides which show compatibility with biological methods are also included owing to their possible suitability in integrated crop management programmes.

Insect-induced chemical changes in young lodgepole pine (Pinus contorta): the effect of previous defoliation on oviposition, growth and survival of the pine beauty moth, Panolis flammea

ABSTRACT. 1. Significantly more eggs were laid by adult female pine beauty moths (Panolis flammea (D&S)) on previously undefoliated lodgepole pine (Pinus contorta Douglas) saplings than on those which had been partially defoliated the year before.

SEASONAL VARIATION IN REPRODUCTIVE POTENTIAL: A PROGRAMMED FEATURE OF APHID LIFE CYCLES

SUMMARY (1) Individuals of six species of aphid from two families were dissected and the number of ovarioles recorded. Variation in ovariole number occurred within and between generations. The spring generation(s) in each species had the highest number. (2) Generations with many ovarioles were more fecund than those with few. In those generations showing variability an individual with a high number of ovarioles was potentially more fecund and reproduced at a greater rate than individuals with few ovarioles. (3) The changes in reproductive potential are programmed and anticipate predictable