Ponds are diverse habitats that make major contributions to regional biodiversity, yet have received relatively little attention compared to other freshwater environments. This study investigated the physico-chemical characteristics and ecology of a nationally important concentration of temporary upland ponds in Radnorshire, Wales in both spatial and temporal dimensions (up to 80 ponds over 18 months). Plant and macroinvertebrate communities were typical of oligotrophic, acidic ponds and appeared to vary along gradients of pH and hydroperiod, whilst including several nationally rare/threatened taxa. A national classification based on the biological community of temporary ponds grouped Radnorshire ponds with a few others in western Britain. Ponds were generally small, shallow and acidic with low concentrations of nutrients and dissolved minerals. Water chemistry was associated with concentration by evaporation and dilution by rainwater, whilst the overall hydrology of ponds was successfully modelled using local meteorological data. Over the course of the study, large increases in macroinvertebrate abundance were observed, but assemblage composition and richness were broadly constant. Seasonality in the abundance of individual macroinvertebrate taxa was evident and suggested that autumn was the optimum time for invertebrate sampling in terms of abundance and diversity. Nearly 40% of the variation among ponds in macroinvertebrate and plant communities was explained by a combination of a species-area effect and differences in pH: no effect of pond isolation was detected within the context of the study region. A cumulative species-area analysis found that a group of small ponds support higher biodiversity than a single large pond of the same area, highlighting the importance of considering beta diversity. Taken together, the findings of this PhD project justify the designation of Radnorshire as an Important Area for Ponds: the ponds form a distinct ‘pondscape’ of >80 waterbodies, with a highly dynamic environment and biota, and which provide a major habitat resource for rare species in the UK.

Lathyrus species are well placed to meet the increasing global demand for food and feed, at the time of climate change, provided that the problem of the neurotoxins is solved. Conservation and sustainable use of the genetic resources of Lathyrus is of significant importance to allow the regain of interest in Lathyrus species in world. A comprehensive global database of Lathyrus species originating from the Mediterranean Basin, Caucasus, Central and West Asia is developed using accessions in major genebanks and information from eight herbaria in Europe. This information allowed to determine gaps in ex situ collections, mainly for wild relatives of cultivated species, and to identify appropriate sites for in situ conservation, mainly in the Fertile Crescent region. Core subsets were identified and the Focused Identification of Germplasm Strategy (FIGS) was used to derive a subset for heat and drought tolerance. This study used morphological characters and AFLP markers to better understand the taxonomic classification of different Lathyrus sections and species and to gain insights on the phylogenetic relationships among them. A Field Guide for Lathyrus L. species of the Mediterranean Basin and Caucasus, Central and West Asia is produced, to ease their identification by non-professional taxonomists.

The non-native predatory phytoseiid mite \(Neoseiulus\) \(californicus\) has been found in recent years in UK apple orchards. The aims of this study were to determine whether this mite could establish in the UK and its potential as a biocontrol agent for \(Panonychus\) \(ulmi\). By reviewing the literature and examining specimens of \(N. californicus.\) it was concluded that taxonomic synonymies with \(Amblyseius\) \( californicus.\) \( Amblyseius\) \(chilenensis\) and \(Typhlodromus\) \( mungeri\) could be supported, but those with \(Typhlodromus\) \( marinus\) and \(Neoseiulus\) \(fallacis\) could not. \(Neoseiulus\) \(californicus\) was found in strawberry, hop, blackcurrant and apple plantations in the main fruit growing regions of the UK. Field and laboratory studies showed that \(N.californicus\) possesses the ability to diapause, is a chill tolerant species and can survive winter field conditions in the UK. \(Neoseiulus\) \(californicus\) was found to readily consume both \( Panonychus\) \(ulmi\) and \(Tetranychus\) \(urticae\) and consumed greater numbers of prey than the native phytoseiid \(Typhlodromus\) \(pyri\). Deutonymphs consumed an average of 1.8 and 1.6 immature \(P. ulmi\) stages per day respectively and an average of 2.6 and 1.4 \(T. urticae\) respectively. The total mean development time for \(N. californicus\) was 7.47 days and for \(T. pyri\) was 12.45, feeding on \(P.ulmi\). \(Neoseiulus\) \(californicus\) from USA, Spain and UK displayed differences in measurements of a selection of morphological characteristics, diapause ability (16, 0 and 960/0 diapause respectively), development times (shortest for USA and longest for UK), fecundity (0.82-0.97 eggs per day) and esterase banding patterns, indicating the existence of different detectable strains. In conclusion, \(N. californicus\) was found to be a component of fruit plantation fauna in the UK, has the potential to survive winter field conditions and readily consumes \(P. ulmi\) and \(T.urticae\).

In order to examine population structure (micro-evolution) in Begonia and its congruence to higher patterns of diversity (macro-evolution), nuclear microsatellite markers have been isolated and applied to two Begonia species, B. socotrana and B. sutherlandii. Begonia socotrana is endemic to the Haggeher Mountains of the island of Socotra in the Indian Ocean, where it has a total range of less than 10 x 15 km. Population surveys have highlighted the need for its conservation status to be reassessed, and it is proposed to reduce its status from 'endangered' to 'least concern'. Population genetic analyses using microsatellite data show a significant degree of population structure (RST= 0.081, P<0.01; q=0.096, P<0.01) and significant isolation by distance, even over small spatial scales. The pattern of isolation by distance could be due to restricted gene flow, or the result of small scale vicariance events in the fragmented peaks of the Haggeher Mountains during climate change and resulting altitudinal migration. Begonia sutherlandii is native to eastern and southern Africa, where it is restricted to shaded, moist banks in indigenous forest. A high degree of population structure was found (q=0.482, P<0.001; RST=0.634, P<0.001), which along with a high number of private alleles reflects the severe isolation of populations in a patchily distributed forest habitat. Population relationships appear to be strongly governed by the history and continuity of forest cover in the region. The population genetic studies of B. socotrana and B. sutherlandii show a strong correlation of genetic variation with geography which reflect patterns seen at larger scales. The correlation of micro and macro evolutionary patterns is congruent with a hypothesis of restricted gene flow promoting speciation in Begonia.

To maintain genetic integrity, eukaryotic cells must faithfully segregate their chromosomes to daughter cells during mitosis. Errors during bi-orientation lead to aneuploidy, a hallmark of human cancers. A highly conserved mechanism termed the Spindle Assembly Checkpoint (SAC) delays the onset of anaphase until all chromosomes have correctly aligned on the metaphase plate. The proteins responsible for the SAC signal include Mad1, Mad2, BubR1 (Mad3 in fission yeast), Bub1, Bub3 and Mph1 kinase. The SAC monitors tension across the spindle and the attachment status of kinetochores; large, proteinaceous structures that assemble on centromeres during mitosis, and is maintained until all kinetochores are properly attached to microtubules. Phosphorylation and dephosphorylation at the kinetochore also regulate chromosome biorientation. Although the SAC has been intensively studied, the exact kinetochore binding site of some SAC components and regulatory mechanisms surrounding the SAC are poorly understood. I have shown, subsequent to previous work which implicated Protein Phosphatase 1 (PP1) in SAC silencing, that two PP1-binding motifs within the N-terminus of kinetochore protein Spc7 (KNL-1 in human cells) bind Dis2, a fission yeast homologue of PP1, in vitro. This interaction is essential for viability and efficient SAC silencing. I also present data implicating kinesin motor proteins Klp5 and Klp6 in PP1-binding and SAC silencing. Furthermore, I have established a role for the Spc7 MELT motifs in recruiting Bub1, Bub3 and Mad3 to the kinetochores using phospho-null (spc7-9TA) and phosphomimetic (spc7-9TE) mutants, and present evidence that this interaction is required for the recruitment of other SAC components. Additionally, the MELT motifs have a role in SAC maintenance and chromosome segregation, and spc7-9TE cells are able to silence the SAC more efficiently than wild type cells. Results presented in this thesis highlight KNL-1 as a major platform for SAC silencing at the kinetochore and will likely form the basis of future studies within the field of mitosis.

There is a growing need to engineer an increased yield in food crops coupled with greater resistance to environmental stresses, such as drought, to meet the requirement of a growing population. As plant responses to drought (and other abiotic stress) are complex, many studies have attempted to understand the drought response in a holistic manner, for example, by analysing transcriptomics data obtained from plants subjected to drought. Preliminary work of obtaining time-series microarray data from a slow-drying experiment of Arabidopsis was used to construct Gene Regulatory Networks using Variational Bayesian State Space Modelling. This led to the identification of a number of transcription factors RAP2.12, FD, BHLH038, ANL2, and two unknown genes, UKTF and POZ, as possibly being important regulatory genes in the drought response. Loss- and gain-of-function mutants of these genes, as well as those of AGL22 identified by Bechtold et al. (2016), were phenotyped under drought conditions. Only the flowering time AGL22 showed a drought phenotype. Network connections in the gene network of AGL22 were tested by qPCR. Drought responsive transcription factors, such as DREB1A and WRKY20 were found to be induced by AGL22.

Atmospheric CO2 levels have been increasing at an accelerated rate for the last 250 years, much of which is absorbed by the oceans, resulting in a process called ocean acidification (OA). This phenomenon has the capacity to disrupt many marine biological processes that utilise carbon, in particular photosynthesis and calcification, and as such phytoplankton have been a main topic of OA studies. While research has accelerated over the last decade, establishing general trends still remains confounded by methodological inconsistencies. Coccolithophores, particularly the species Emiliania huxleyi, are both ecologically and biogeochemically important phytoplankton; however, one strain (NZEH) has produced highly varied results. Here, we present a multivariate analysis that suggests previous inconsistencies between past studies of NZEH may be driven by variance of the light:dark (L:D) cycle used for growth. Experimental analysis on NZEH showed that under a 14:10h L:D cycle, CO2 induces significantly slower growth rates and higher PIC and POC cell-1, but this effect is dampened under 24h of light. This was widened to encompass more taxa, including more isolates of E. huxleyi (PLY70-3, PLY124-3, RCC962), and two other species of coccolithophore; Gephyrocapsa oceanica and Coccolithus pelagicus. L:D cycle changed the observed OA response, with two main responses divided by biogeographical origin. In tropical taxa, 24h light enhanced the effects of increased photosynthesis, but dampened the decrease in calcification in response to CO2. For temperate taxa, 24h dampened both the increases in photosynthesis and calcification with CO2. Evaluation of photobiology reveals that both CO2 and longer photoperiods induce a “high light” acclimation response, and changes in coccosphere thickness suggest it has a photoprotective role. Finally, results from bioassay experiments on natural phytoplankton populations in the polar regions show that CO2 response is hard to predict and based on community composition and ambient starting conditions. This work serves to further highlight the importance of environmental variables that moderate the OA response in accurately understanding future biogeochemical cycles. Future models attempting to predict the impact of OA upon marine systems must critically account for interactive role of light availability.

Sporophytic self-incompatibility is a genetically controlled inbreeding prevention mechanism, which is prevalent in the Brassicaceae, and has been reported in a variety of high profile species. Despite the benefits of preventing self-fertilization in terms of maintaining genetic diversity, variation in the strength of self-incompatibility (SI) has also been well documented, as has a shift from SI to inbreeding at the species and population levels. An important underlying driving force behind a switch to inbreeding could be the reproductive assurance provided by not requiring an unrelated mating partner for sexual reproduction. This could be beneficial for a species undergoing rapid colonization, because only a single individual is required to begin a sexually reproducing colony after a long-distance dispersal event (Baker’s law), which is characteristic of the plight of many species after the last glacial maxima. The purpose of my thesis was to evaluate the effects of variation in mating system on post-glacial colonization, using two model species that show intraspecific variation in outcrossing rates. The first, Arabidopsis lyrata, represents an excellent model system to assess post-glacial colonization history because it exhibits broad geographical and ecological ranges, and has a recently completed genome sequence. In North America, A. lyrata has further benefits as a model system, namely it exhibits variation in the strength of SI and shift to SC at the population level, which is not observed in Europe. The second species is Arabis alpina, which also appears to show population level variation in mating system strength in Europe based on variation in FIS. This has been putatively linked to colonization history after the last glacial maxima. Unlike in A. lyrata however, its mating system has not been characterized. Mating system delimitation in A. alpina has the potential to aid the interpretation of patterns of ecological genetic diversity, which may in part be influenced by local or regional stochastic changes to mating system variation. My first objective was to identify if A. alpina had a functioning SI system based on both self-fertilization experiments, and allozyme based outcrossing rate estimations. I found strong evidence to suggest the presence of a functional barrier preventing self-fertilization in A. alpina. I identified multiple putative SRK alleles (the female determinant of self-incompatibility), suggesting that the same type of sporophytic system seen in other Brassicaceae species governs SI in this species. I also demonstrated linkage of SI phenotype to some SRK genotypes by diallel crosses, strengthening the case for a functional SI system in this species. Further to this I demonstrate variation in mating system strength between populations, and autonomous inbreeding was seen in a single population. I note that the potential changes in SI status coincide with areas suspected to differ in post-glacial history based on allozyme diversity reported in previous work. While the number of populations sampled was insufficient to link mating system variation to colonization history in A. alpina, mating system variation has been more extensively characterized in North American A. lyrata, allowing more fine-scale resolution of population structure and post-glacial colonization history; an underlying objective of my thesis. I used three molecular marker systems (cpDNA, nuclear micro-satellites and allozymes) to assess these phylogeographic questions, and present evidence of three putative colonization routes for the Great Lakes region. These putative routes are congruent with those described in other species, particularly amphibians and reptiles. Further to this I considered the possible location of glacial refugia, and likelihood that plant taxa may have survived during Pleistocene glaciation in close proximity to the Laurentide Ice Sheet, particularly in Illinois, Indiana, Wisconsin and Minnesota, which may also be true for some animal taxa. I examined patterns of population structure, and scenarios that may have influenced this, and present support for the previously documented theory of multiple breakdowns in SI in this geographic region. My final objective was to assess the suitability of the three marker systems for phylogeographic reconstruction in A. lyrata, by comparing and contrasting the patterns of population structure, and colonization history suggested by each system. Levels of variation observed between the marker systems used varied, and I explored how these patterns complemented and contradicted each other. As expected, the nuclear micro-satellite loci represent the system with the greatest genetic diversity, but do not allow meaningful conclusions to be drawn regarding colonization history because of low levels of shared variation between populations. Conversely, the allozyme loci presented much lower levels of genetic diversity, but support population structuring conclusions based on both cpDNA data and previous studies of A. lyrata and other taxa in this area. The cpDNA marker (trnF) represents a somewhat contentious system to use for phylogeography in A. lyrata, as it contains a tandem array of highly variable, but complexly evolving duplications (pseudogenes). I concluded that these structural changes could be phylogenetically informative when pseudogene evolutionary relationships can be resolved This was based on variation in patterns of diversity, and the subsequent population structure change that occurred when using different methods of assessing trnF variation.

The aim of this project was to try to find the mode of action of azadirachtin in cultured cells, and to compare its cytotoxicity with some well-known phytochemical pesticides. The results presented here showed that azadirachtin was toxic to the cultured insect cells used (Sf9 and C6/36, derived respectively from Spodoptera frugiperda and Aedes albopictus) even in very low concentrations with an EC50 for the Spodoptera cells estimated at 5x10-9 M, but that the mammalian fibroblast cell line L929 was little affected except at concentrations greater than 10-4M. The other major neem terpenoids, nimbin and salannin, showed low toxicity towards the cultured cells. The neurotoxic pyrethrum showed little effect against the cultures, except for some slight stimulatory effect on growth at 10-8 M. Rotenone, known to inhibit the electron transport chain, effectively inhibited the growth of both insect and mammalian cells. Nicotine, another neurotoxic phytochemical, had little effect on the growth of the cultured cells. It was concluded that while cell growth assessment is not appropriate for all phytochemical pesticides, it is useful for those, such as azadirachtin and rotenone, whose effect is on the essential mechanisms of insect cells in general. Rotenone was used as a positive control to investigate if azadirachtin had its effect on respiration of the cells. Only at the highest feasible concentration of azadirachtin, was there a slight but significant (15%) reduction of respiration which was the same in both insect and mammalian cells. As expected, rotenone inhibited both insect and mammalian cells even at concentrations as low as 10-11 M. When the effects of azadirachtin on the cell cycle were examined by means of cell cytometry, it was shown that the compound arrested the cell-cycle in G2/M phase, and that the effect was related to the concentration. Microscopy confirmed that there was a three-fold increase in the mitotic index after 2 hours of exposure of 2x10-6 M azadirachtin. The similarity of the of the nuclear profiles and cell-cycle distribution to Sf9 cells treated with colchicine, a well-known antimitotic phytochemical, suggested there was a similarity of action between the two compounds.

Mangroves are a group of woody plants that occur in the dynamic tropical and subtropical intertidal zones. Mangrove forests offer numerous ecosystem services (e.g. nutrient cycling, coastal protection and fisheries production) and support costal livelihoods worldwide. Rapid environmental changes and historical anthropogenic pressures have turned mangrove forests into one of the most threatened and rapidly vanishing habitats on Earth. Yet, we have a restricted understanding of how these pressures have influenced mangrove abundance, composition and functions, mostly due to limited availability of mangrove field data. Such knowledge gaps have obstructed mangrove conservation programs across the tropics. This thesis focuses on the plants of Earth’s largest continuous mangrove forest — the Sundarbans — which is under serious threat from historical and future habitat degradation, human exploitation and sea level rise. Using species, environmental, and functional trait data that I collected from a network of 110 permanent sample plots (PSPs), this thesis aims to understand habitat preferences of threatened mangroves, to explore spatial and temporal dynamics and the key drivers of mangrove diversity and composition, and to develop an integrated approach for predicting functional trait responses of plants under current and potential future environmental scenarios. I found serious detrimental effects of increasing soil salinity and historical tree harvesting on the abundance of the climax species Heritiera fomes. All species showed clear habitat preferences along the downstream-upstream gradient. The magnitude of species abundance responses to nutrients, elevation, and stem density varied between species. Species-specific density maps suggest that the existing protected area network (PAN) does not cover the density hotspots of any of the threatened mangrove species. Using tree data collected from different salinity zones in the Sundarbans (hypo-, meso-, and hypersaline) at four historical time points: 1986, 1994, 1999 and 2014, I found that the hyposaline mangrove communities were the most diverse and heterogeneous in species composition in all historical time points while the hypersaline communities were the least diverse and most homogeneous. I detected a clear trend of declining compositional heterogeneity in all ecological zones since 1986, suggesting ecosystem-wide biotic homogenization. Over the 28 years, the hypersaline communities have experienced radical shifts in species composition due to population increase and range expansion of the disturbance specialist Ceriops decandra and local extinction or range contraction of many endemics including the globally endangered H. fomes. Applying habitat-based biodiversity modelling approach, I found historical tree harvesting, siltation, disease and soil alkalinity as the key stressors that negatively influenced the diversity and distinctness of the mangrove communities. In contrast, species diversity increased along the downstream – upstream, and riverbank — forest interior gradients, suggesting late successional upstream and forest interior communities were more diverse than the early successional downstream and riverbank communities. Like the species density hotspots, the existing PAN does not cover the remaining biodiversity hotspots. Using a novel integrated Bayesian modelling approach, I was able to generate trait-based predictions through simultaneously modelling trait-environment correlations (for multiple traits such as tree canopy height, specific leaf area, wood density and leaf succulence for multiple species, and multiple environmental drivers) and trait-trait trade-offs at organismal, community and ecosystem levels, thus proposing a resolution to the ‘fourth-corner problem’ in community ecology. Applying this approach to the Sundarbans, I found substantial intraspecific trade-offs among the functional traits in many tree species, detrimental effects of increasing salinity, siltation and soil alkalinity on growth related traits and parallel plastic enhancement of traits related to stress tolerance. My model predicts an ecosystem-wide drop in total biomass productivity under all anticipated stress scenarios while the worst stress scenario (a 50% rise in salinity and siltation) is predicted to push the ecosystem to lose 30% of its current total productivity by 2050. Finally, I present an overview of the key results across the work, the study’s limitations and proposals for future work.