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This thesis explores the relative importance of within-patch habitat quality, the temporal persistence and spatial connectivity of habitat patches, for heathland ground beetle assemblages in a forested and open habitat landscape mosaic of Breckland, Eastern England. Comparison of the carabid fauna of two distinct landscape elements: remnants of once extensive lowland heathland and the pine plantations of Thetford Forest managed by rotational clear-felling, showed the high value of the forest landscape for carabid species restricted to grassland, heathland and sandy habitats (GHS). Within the forest landscape, temporal changes in carabid community in planted stands are determined by management and succession, with conditions suitable for GHS species persisting for just seven years after replanting. For persistence of GHS species within Thetford Forest permanent open space, representing approximately ten percent of the area, is essential. Habitat quality, particularly greater cover of bare sand, lower sward and shallow soil litter, were more important predictors of patch suitability for GHS species than patch size. Suitability of linear trackway elements within the plantation was determined by the surrounding matrix, with high GHS species richness in trackways surrounded by younger plantations (<20 years) and very few GHS in those surrounded by older plantations. Behaviour of the model arenicolous species Harpalus rufipalpis differed between these two types of trackways, with greater levels of activity and more leakage in poor quality trackways surrounded by older trees; thus only a subset of trackway elements will serve as corridors for conduit. Despite the interrupted nature of this network, colonisation of newly created clear-fells by GHS species was not affected by their isolation, at least at the current scale of management. Almost all GHS species recorded in permanent open habitats were shown to successfully colonise ephemeral open patches: colonists did not represent a subset of GHS species and were not filtered by dispersal ability.

This thesis describes studies on population variation in laboratory-reared cultures of the Larger Grain Borer, Prostephanutsru ncatus( Horn) (Coleoptera: Bostrichidae). Prior to its introduction into Africa around 1980, P. truncatus was not regarded as being of major economic importance. However, it has since become a major pest of stored maize and dry cassava in Africa causing over £500 million of damage per year. In order to gain a better understanding of the biology of P. truncatus, genetic, morphological and feeding behaviour variability were studied in six laboratory maintained populations collected from single locations: four from Africa (Tanzania, Kenya, Togo and Nigeria) and two from Central America (Costa Rica and Mexico), plus one recently collected field population from Tanzania. Three techniques were used: 1. Cellulose acetate enzyme electrophoresis, 2. Morphometrics and, 3. Behavioural observations, in order to explore potential usefulness of these methods in the study of geographical variation between P. truncatusp opulations. Allozyme electrophoresis (using cellulose acetate gel) as performed in this study showed that genetic variation existed in P. truncates. Of the ten enzyme loci screened, four (phosphoglucoisseo meraceg,lu tamate-oxaloacetatrtaen saminasep,e ptidarea nd malic) revealed clear variation among some of the six laboratory populations. The proportion of polymorphic loci (P) for the six populations was found to be 0.75 and the mean heterozygosity ( H) 0.247 (Togo had the highest- H=0.336 and Costa Rica the lowest- H= 0.141). Comparison of allele frequencies showed significant differences between some of the six laboratory populations (P < 0.001). Pairwise comparisons between allele frequencies for the four polymorphic loci revealed large differences in allele frequencies between the African and Costa Rican populations and great similarities in allele frequencies between African and Mexican populations. This suggests that the African populations are more closely related to the Mexican population and may first have been introduced to Africa from Mexico. No significant allele frequency differences were found between the field and laboratory reared populations from Tanzania. The morphometric study was carried out using seven male characters and nine female charactersT. he results showed that most characters( exceptf our: hindspur and hindtibia for males, and forespur and midantennal segment for females) revealed significant morphological variation between some of the six laboratory populations. All the tests: Univariate Analysis of Variance, Multivariate Analysis of Variance, Discriminant Function Analysis and Principal Components Analysis showed significant population differences. The Costa Rican population showed distinctive morphological differences from the other five populations. The recently collected field population shared similar morphological characters with laboratory reared population from Kenya. The behavioural study focused on variation in the relationship between progeny production and the degree of damage caused to maize grain and dry cassava. After eight weeks, standardised cultures differed significantly with respect to the total number of adults and larvae recorded at the end of the experiment (the populations from Mexico and Kenya had the highest number while the population from Costa Rica had the lowest). When the degree of stored product damage was considered, significant differences were again found, and the ranking was similar. The damage done was significantly correlated with the number of progeny produced (P < 0.001). Comparison of results obtained from laboratory maintained African populations with a field sample obtained from Tanzania indicates the potential usefulness of cellulose acetate electrophoresis of allozymes and morphometrics in the study of geographical variation in African P. truncatesT. his will lead to a better understanding of the biology of this economically important insect and provide more solid data on which to base control measures.

The sex pheromone system of Stegobium paniceum (L.) was studied in the laboratory by means of live female assay experiments as well as extraction of the pheromone from females using solvent and volatilisation techniques. Female beetles were shown to attract only males, which were themselves attractive to neither sex. Female Stegobium were capable of controlled pheromone emission even when body content levels were high. Newly eclosed females contained small quantities of pheromone which reached maximum levels in 6 to 9-day-old insects. Very little emission occurred until females were 2.5-3.5 days old, after which maximum emission rates were reached rapidly between days 3 and 4, the age at which the first mature oocytes were found in the calyx of female ovaries. A series of dilutions of solvent pheromone extracts were bioassayed with males and a theoretical minimum threshold level of response extrapolated to 0.0004 female equivalents. By comparison with a "wild" strain of Stegobium it was suggested that mass rearing over a long period increased male sensitivity to the pheromone but lengthened the period necessary to reach maximum response levels after adult emergence. Mating slightly reduced female pheromone content, but pheromone emission fluctuated markedly after mating for reasons not fully understood. The number of eggs laid per female increased from about 1.5 to over 40 if copulation occurred. Male presence during oviposition increased the percentage of females producing eggs but decreased the number of eggs laid per female of those laying. This reflects decreased fertility of females with age. The antennal sensilla of Stegobium were surveyed by means of light and scanning electron microscopy. The main types present were trichoidea, basiconica, chaetica and coeloconica, and there was no apparent sexual dimorphism of sensilla numbers or distribution. Male antennectomy completely inhibited sex pheromone response and progressive removal of club segments increasingly diminished male response intensity.

Scaritinae are a subfamily of ground beetles (Carabidae), containing about 1900 species and 125 genera. They share a distinctive body shape linked to a burrowing lifestyle. The diversity of Scaritinae is concentrated in the tropics and warmer regions of the southern hemisphere, particularly Southern Africa, Madagascar and Australia. The evolutionary history (phylogeny) of scaritines is unknown, leading to conflicting classification schemes and uncertainty over the definition of genera, especially in one subgroup of scaritines, the tribe Scaritini. In particular, it is unclear whether Scaritinae are descended from a common ancestor (monophyletic) or whether they are an artificial group defined by convergent adaptations to burrowing. Phylogenetic relationships of the Scaritinae were investigated in detail for the first time using morphological and molecular data. Analysis of morphological characters resulted in multiple equally parsimonious trees. Bayesian analysis supported a monophyletic Scaritinae and within Scaritini, a basal position of subtribes Carenina and Pasimachina. Relationships of subtribe Scaritina were impossible to reconstruct due to a complex pattern of convergent evolution and character reversals. 18S rRNA gene sequences were aligned using ClustalX and by incorporating secondary structure information using MAFFT. Consistent results were obtained by Bayesian analysis of the MAFFT alignments, supporting the clades Scaritinae and Scaritini, Carenina and Scaritina. The Australian scaritines (Carenina) were found to be sister to all remaining Scaritini. An historical biogeographic reconstruction of the Scaritini was undertaken by incorporating evidence from extant distributions, fossils and the phylogenetic data. It is likely that evolution of the basal lineages of Scaritini occurred before the fragmentation of Gondwana and that the present-day distributions of the later radiation of Scaritina are due to dispersal. As with most groups of Carabidae, the lack of fossil evidence and molecular clock dating precludes any firm biogeographical conclusions.

Saproxylic beetles feed on decayed dead wood, representing some of the most ecologically important fauna in mature forests dominated by veteran trees, though this habitat is a shadow of its former self in Britain and Europe; confined to a handful of unconnected sites it remains nationally important for the diverse community assemblage it supports. Saproxylics can mediate and manipulate the fungal decay of wood, though this knowledge about the keystone status of saproxylic beetles is still poorly understood, despite some saproxylic beetles being some of the largest and most charismatic invertebrates in Europe. Habitats for saproxylics have been carved up over the course of human development, whilst forestry management practices encouraged the ‘tidying up’ of woodland by removing dead wood, leading to localised extinctions of saproxylics throughout Britain and Europe. Even in cases where extinction/threatened statuses are formally recognised servicing of conservation plans is constrained by limited understanding of their biodiversity. In this research the development and application of a suite of morphological, genetic, and ecological simulation approaches to characterise various components of saproxylic beetle diversity is described. This study focusses on three saproxylics: the Stag Beetle (Lucanus cervus), the Noble Chafer (Gnorimus nobilis), and the Bee Beetles (Trichius spp.). For Stag Beetles, the first microsatellites were developed and utilised along with mitochondrial (mtDNA) Cytochrome Oxidase 1 sequencing to perform a preliminary genetic analysis. mtDNA supported the predominance of a single clade across the species’ distribution which exhibited signatures of historical expansion/contractions linked to glacial/interglacial periods. Both mtDNA and microsatellites revealed a markedly lower level of genetic variation among UK samples compared to continental European counterparts and the implications for sustainability and remedial actions are discussed. For Gnorimus nobilis, a rot-hole specialist confined in England to traditional orchards, geometric and mtDNA sequence analysis characterised and confirmed differences between it and its relative, the Variable Chafer (G. variabilis), as well as supporting recognition of other proposed sub-species. A salient feature of the intraspecific genetic variation was the deep divergence between the Eastern and Western clades, indicating historical vicariance and limited post-glacial overlap between clades. For Trichius, analysis of three distinct species revealed three reciprocally monophyletic mtDNA clades. However, despite support for three distinct morphotypes, there was a high level of mtDNA/ morphological incongruence, i.e. multiple morphotypes were associated with a single clade. Nuclear DNA sequencing supported the hypothesis that the pattern has been generated by historical vicariance and introgression upon secondary contact. Species Distribution Modelling of multiple saproxylics (n=14) indicated that many species had similar glacial refugia: a northern refugium across France and Germany was predicted for many species. In addition, many species were predicted to find the Mediterranean region increasingly unsuitable under climate change simulations, but are also predicted to find suitable climates opening up toward the north-east of Europe. The project represents the first combined study of morphological taxonomy, phylogeography, population genetics and habitat modelling in rot-hole associated beetle species across Europe, and should help direct conservation efforts for these and other saproxylic beetles.

Bruchid beetles are economically important pests of grain legumes. Their medium to high level infestation is being controlled with insecticide. This study investigated the effects of environmental factors such as temperature, toxicant concentration, food and bruchid geographical strain on malathion tolerance in Callosobruchus species (c. maculatus, C. chinensis and C. rhodesianus). There were variations in insecticide tolerance among the species and C. maculatus which is the most widely spread and known showed the highest tolerance. Geographical origin had a pronounced impact on the response of C. maculatus to malathion. There was a positive relationship between temperature effect and bruchid susceptibility to malathion as often observed with organophosphate. The impact of food on insecticide tolerance in Callosobruchus was quite unpredictable. Overall, the interactive effects of all the factors are very complex. An alteration of anyone factor could either enhance or reduce tolerance. This could be driven by bruchid ancestry or fitness cost. Biochemical pathway study with malaoxon (malathion metabolite) ruled out acetylcholinesterase (AChE) as primarily responsible for malathion tolerance in bruchids; though it could be an additional factor to other tolerance mechanisms. However, there was variation in AChE activity among the species and strains with influence from the rearing food. Preliminary screening of the bruchids for the endosymbiont Wolbachia, prior to studies on its effect on insecticide tolerance was undertaken. The study revealed a high probable presence of this organism in C. maculatus and C. rhodesianus, which were previously thought to be non-host species. The implication of these findings in order to optimize bruchid management especially with insecticides to avoid/combat the development of insecticide resistance is discussed. This includes the impacts on legume breeding, production, transportation and storage.

No organism evolves in isolation; the symbiotic microorganisms associated with insects are key determinants of their hosts ecology and evolution. This thesis investigates the fungal communities found with bark and ambrosia beetles (Curculionidae: Scolytinae & Platypodinae) in an attempt to better understand the diversity and variability of this ecologically and economically important system. I start by assessing the efficacy of high throughput sequencing (HTS) and metabarcoding for the characterisation of fungal communities derived from whole arthropod DNA extracts (Chapter 2). I then apply this approach to understanding the biotic and abiotic determinants of beetle associated fungal taxa, and find that both beetle species identity and environmental conditions significantly predict community richness and composition (Chapter 3). In Chapter 4, I expand upon the beetle species level differences in microbial communities to show that they are driven by a relatively small subset of fungal taxa, predominantly belonging to the beetle associated Microascales, but also to the relatively unexplored Saccharomycetes. I further apply HTS to the recreation of beetle evolutionary histories using mitochondrial genomics, and test for correlations between beetle phylogenetic and mycobiotic similarities (Chapter 5). My investigations demonstrate the utility of recently developed sequencing technologies to the study of microbial symbioses and I conclude with a synthetic summary of my findings with suggestions for further research.

No description available.