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Approximately 29,000 ha of grass buffer strips in the UK have been established under Agri-Environment Schemes with the objective of mitigating intensive arable management practices that have negatively impacted on invertebrate and plant biodiversity. However, typically these strips are floristically poor and as such offer limited biodiversity value. This study aimed to identify management practices to enhance the biodiversity value of existing grass-only buffer strips on three farms in Southern England. An initial scarification to create germination niches was applied in combination with a wildflower seed mixture. The effectiveness of a graminicide (fluazifop-P-butyl) for controlling the competitive dominance of grasses at different rates and timings was also investigated. Responses of wild flowers and grasses, insect pollinators and spiders were monitored for up to four years after establishment. The combination of scarification, sowing and graminicide resulted in the highest cover, species richness, and diversity of wildflowers, and greatest sward heterogeneity. The benefits of establishing sown wildflowers within the existing buffer strips were highlighted by the positive responses observed for both insect pollinators and spiders, and is likely to reflect greater foraging resources and prey availability respectively. A glasshouse study was also conducted to investigate pre- and post-emergent fluazifop- P-butyl applications on the wildflower species in the seed mixture, and demonstrated no long-term effects following application at the recommended rates for buffer strips. The results of the field and glasshouse studies demonstrate that managing existing grass buffer strips with a combination of scarification, sowing and graminicide, can significantly enhance biodiversity. Further studies at a national scale are essential to convince farmers and policymakers of the widespread applicability and reliability of this approach. If this is achieved then incorporating these management tools into future agri-environrnent options could deliver benefits to pollinating insects, spiders and other components of biodiversity. vi.

Biodiversity, arising at multiple levels, is known as a multi-dimensional and complex concept, but is also known to have a rather loose definition. Imprecise definitions are not very suitable for objective quantification or the rigour of economic valuation. Therefore, to construct a more substantial definition of value for biodiversity, a theoretical argument aiming to link biodiversity and functional (meaningful) information needs to be developed. A working hypothesis is that biodiversity is a measure of the total difference within a biological system, which can be summarised in terms of the system's total information content, of which functional information is a subset. Since functional information has systematic (non-random) Patterns, it therefore, coincides with the scientific meaning of biological complexity, thus providing the foundation of value in biodiversity. The theory presented sets the goal of estimating biological complexity from the potentially valuable information derived from empirical biodiversity metric data (ecological measures). To achieve this, the ecological properties ofa system, as they are measured by ecologists, were translated into a simply defined single valued property. This led to a conclusion that ifthere exists a systematic relationship among empirical biodiversity metrics, then there must be a unifying property underlying intrinsic value ofbiodiversity. Then, an advantage of a representation of biodiversity as information was demonstrated by comparing it with the most commonly used metric - species richness. It was shown that species richness missed a large proportion of diversity, emphasising the importance of additional ecological properties and the need for species databases to record functional traits, presence and abundances in communities, as well as phylogenetic information. Finally, by providing intellectual foundations and developing an analytical tool for biodiversity quantification, this study sets the goal for further research.

The Convention on Biodiversity (CBD) signed at the 1992 Earth summit in Rio formally recognized biodiversity at the habitat, species, and genetic levels. For species and habitat biodiversity there is a well-established set of frameworks under which conservation programmes are constructed and delivered. From a genetic biodiversity perspective, however, there is no clear consensus on how best it should be measured, or how conservation programmes should be implemented. The major reasons for conserving intra-specific genetic biodiversity can be summed up under two inter-related themes, (1) Protecting a broad spectrum of genetic biodiversity, and (2) Maintaining evolutionary fitness and adaptive variation. This thesis takes a case-study approach and explores the issues surrounding these themes for conservation strategies in two angiosperm species: Saxifraga hirculus and Lathyrus japonicus. 1) Protecting a broad spectrum of genetic biodiversity: This section of the thesis considered the evidence for major intra-specific genetic races in Saxifraga hirculus and the spatial distribution of its genetic biodiversity. Variation in Saxifraga hirculus chloroplast DNA was assessed in order to gain information on the biogeography of the British populations in the context of the wider European gene pool, and also to compare this with populations from Alaska and Colorado. In a European context, British popUlations have a high level of chloroplast diversity (three haplotypes) and contain a highly divergent lineage that was previously unsuspected. Seven haplotypes were found in total from 17 popUlations in Europe with marked inter-population differentiation (FST = 0.92). Higher diversity and lower popUlation differentiation was detected in Alaska (33 haplotypes /12 populations; FST = 0.46). Since most popUlations in Europe had unique haplotypes it is not possible to track migration routes or pinpoint refugia for the European popUlations, but the much higher diversity in Alaska compared to Europe indicates that the Beringia region may have acted as a refugium for this species throughout the Pleistocene. This highlights the importance of Alaska for the conservation of intra-specific genetic biodiversity in this species. (2) Evolutionary fitness and adaptive variation: To assess the relationship between population size, genetic variation, morphological variation and fitness, genetic studies were undertaken on populations of Lathyrusjaponicus. Eleven populations of L. japonicus were examined for variation using nine microsatellite loci. The populations show genetic isolation by distance across the distribution of the species in Britain, although isolation by distance breaks down when only the range centre populations are considered. There was no relationship between population size or isolation and genetic variation, with some small and/or isolated populations having high diversity, and large and/or range centre populations having low diversity. There was, however, a significant difference in the inbreeding coefficient of adult versus seedling plants. The heterozygosity of adult plants sampled in the field was significantly higher than seedlings grown in cultivation, indicating a survival advantage for heterozygotes. Significant differences were found between populations for seed weight, number of seeds per pod, number of pods per cluster, and leaf shape of L. japonicus individuals in the field. For seedlings grown in common conditions significant differences were found in leaf shape, pigmentation, and dry weight after two season's growth. Morphological and genetic differentiation were well matched in this species, and gave similar signals. Seedlings from Carnoustie (Scotland) grew much more vigorously in cultivation in Edinburgh than seedlings sourced from English populations, indicating local adaptation. However no significant relationship was found between any fitness associated traits or morphological variation with genetic variation, in spite of the heterozygote advantage revealed by the genetic data. The results from both research themes are discussed highlighting the difficulties in equating patterns of genetic marker variation to traits likely to be of evolutionary and ecological relevance.

The modelling of biological communities is important to further the understanding of species coexistence and the mechanisms involved in maintaining biodiversity. This involves considering not only interactions between individual biological organisms, but also the incorporation of covariate information, if available, in the modelling process. This thesis explores the use of point processes to model interactions in bivariate point patterns within a Bayesian framework, and, where applicable, in conjunction with covariate data. Specifically, we distinguish between symmetric and asymmetric species interactions and model these using appropriate point processes. In this thesis we consider both pairwise and area interaction point processes to allow for inhibitory interactions and both inhibitory and attractive interactions. It is envisaged that the analyses and innovations presented in this thesis will contribute to the parsimonious modelling of biological communities.

The creation of biodiversity involves the evolution of new species. Recent trends in the study of speciation have increased the emphasis on the role of ecology in adaptation and the evolution of reproductive isolation. This includes examining the relative contributions of different types of selection, the role of gene flow and the genomic changes that occur during ecological speciation. The search for speciation genes continues, however our growing knowledge of how the genome translates into phenotypes means we should now consider a broader molecular basis of speciation, which includes genetic, transcriptomic and potentially epigenetic variation that contribute to phenotypic variation. This thesis addresses the molecular basis of speciation by using three different complementary methods to examine the early stages of ecological speciation and the evolution of premating reproductive isolation between two incipient species of the cactophilic fly, Drosophila mojavensis. First, the genetic basis was examined through the sequencing of two candidate genes underlying reproductive isolation (Chapter 2). Second, the historical biogeography of population divergence was uncovered using multiple sequenced loci (Chapter 3). Lastly, gene expression across the whole transcriptome associated with phenotypic plasticity and mating success was assessed (Chapter 4). Further, the role of epigenetic imprinting in the population divergence of a freshwater fish, Girardinichthys multiradiatus, was examined through sequencing of a well known gene involved in sexual conflict (Chapter 5). These studies find that uncovering the genetic variation underlying speciation is difficult, especially when there is extensive phenotypic plasticity. Further, gene expression plasticity may play an important role in the evolution of premating isolation, and this includes a role for epigenetic mechanisms of gene expression. Additionally, it is important to assess the demographic scenario of population divergence to put into context the ecological and functional data on divergent groups. Through these studies this thesis examines the genetic, expression and epigenetic variation associated with on-going population divergence, and emphasises the need to consider the potential role of the full range of gene expression changes during ecological speciation.