Policy-makers increasingly need to use scientific data that are imprecise. This problem is particularly apparent for marine mammal management issues, where practical research constraints leave scientists and managers with the problem of drawing inference from sparse data. Effective use of such data therefore places great demands on our methods of data analysis and statistical inference. In this thesis I introduce novel Bayesian methods for the analysis of data on marine mammal abundance and trends. Bayesian methods are applied to a suite of case studies to inform current management issues of importance both in the UK and overseas. These include estimating the probability of density dependence in the growth of a killer whale (Orcinus orca) population inhabiting the inshore waters of Washington State; estimating the size of a widespread population of bottlenose dolphins (Tursiops truncatus) in the Bahamas; and assessing the population status and abundance trends of bottlenose dolphins within a newly designated Special Area of Conservation in the Moray Firth, NE Scotland. Each of these case studies uses model-based analysis of individual photo- identification data to make inference about unknown population parameters of interest. Specifically, Bayesian inference, based on "posterior" probability distributions and statements, is used to facilitate scientific reporting in the face of uncertainty about these unknowns. Additional issues addressed are the selection of alternative statistical models for inference based on posterior model probabilities; incorporating model selection uncertainty into inference through the estimation of model-averaged parameter estimates; and the use of random effects prior distributions to model the relatedness between unknown parameters and increase estimate precision. The application of these methods is accomplished through the use of Markov chain Monte Carlo sampling methods, which are implemented using the WinBUGS software.

Regeneration of colonising species following disturbance of primary tropical rain forest in Malaysia was studied in artificial gaps ranging in size up to 30% canopy openness. Effects of gap size on soil temperature and water status were investigated. Spatial variation in density and composition of the soil seed bank beneath undisturbed forest was assessed by germination from soil samples, and seed rain was sampled using seed traps. Seed germination, seedling survival and seedling growth were monitored for two years in gaps and beneath intact canopy. Effects on colonisation of gap size, disturbance to microsite and competition from advance regeneration were studied. Maximum soil temperatures increased with gap size but minimum temperature was unaffected. Soil water content showed no relationship with gap size, but might be higher in gaps than forest after dry periods. Primary forest soil seed bank density was very high (mean 1904 seeds m-2). Climbing shrubs/lianes contributed approximately 75% of seedlings and 50% of taxa. Trees accounted for about 25% composition of taxa, but only 15% of seedlings. Soil seed bank composition differed little among primary forest sites. Similarities in composition between one site and secondary forest possibly reflected recent disturbance. Current seed rain intensity was low, very variable, and not consistently different between gaps and closed forest. Germination in the two years after gap creation was < 5% of the soil seed bank, and appeared greatest in medium-sized gaps. Most germination and accession of new taxa occurred in year one, but both continued at low levels during year two. Ordination analysis suggested that some colonising species regenerated only in large gaps. Both exposure and scarification of the soil increased germination, but had no consistent effects on seedling survival or growth. Competition from advance regeneration was potentially important, increasing mortality and reducing maximum growth rate among colonising seedlings.

The ecology of small rodents was studied in Ghana on a farmland and in a primary forest that has been free from human interference for more than 100 years. The commonest species of rodent on the Farmland was Praomys natalensis which comprised 45.3 percent of the trappable population. In the Primary Forest the commonest species was Praomys stella which comprised 79.7 percent of the population. The Farmland supported a more diverse rodent fauna than did the Primary Forest. This is the first report of Steatomys cuppedius in Ghana. Both the estimated population density and standing crop biomass were higher for rodents living on the Fairmland than for those living in the Primary Forest. The species of rodents in both habitats showed seasonal changes in population sizes as a result of the effects of seasonal changes in rainfall, food availability, and variations in the influx of new individuals into the study area. Peaks in population sizes in most cases were mainly influenced by the influx of immigrants. The mean minimum longevity of the resident population in both habitats ranged from 3 to 4.2 months; and the survival rate estimates of most species were lowest during the major rainy season. Breeding in the Farmland rodents was possible, throughout the year with peaks towards the end of the rainy seasons. In the Primary Forest breeding in Praomys stella was also possible throughout the year but unlike the farmland rodents only a relatively small proportion (20-50 percent) of the adult females were pregnant or lactating in most months. Breeding in males in both habitats was continuous throughout the year and without any clear-cut seasonality. Praomys stella in the Primary Forest had the largest home range among the rodents studied. With the exception of Lophuromys sikapusi ull the rodents showed overlapping home ranges. In Lophuromys sikapusi home ranges of individuals of the same sexes did not overlap and on the basis of this and other evidence it has been suggested that Lophuromys sikapusi might have territory.

This study investigates avian fig-eating and Ficus seed dispersal in a patch of lowland rainforest at Kuala Lompat, Peninsular Malaysia, in the period March 1984 to April 1987.Of 38 Ficus species identified in c.2 km2 of forest, 29 possessed seeds primarily dispersed by birds. A phenological study of these species showed that figs were available in every month, and that the Ficus community exhibited distinct aseasonal fruiting rhythms. Nevertheless, crops of large figs (>25mm mean dimension) were rare, with only 13--16 large-fruited fig-patches per km2 of forest per year. The 60 bird species which ate figs at Kaula Lompat partitioned the fig resource according to fruit size, even though the soft nature of figs enabled birds of all sizes to feed on figs of all sizes. All birds, except some pigeons, rapidly defaecated ingested Ficus seeds. Treron pigeons were specialised fig-seed predators, and were found to eat large proportions of some fig crops; c.30% in one studied fruiting. Radiotracking and observations of foraging birds showed that many species stayed close to large fruit patches. As a consequence of this behaviour, and rapid gut-passage rates for Ficus seeds, seed shadows of bird-dispersed Ficus are anticipated to be leptokurtic. The most important Ficus seed dispersal agents, in terms of long distance dispersal, are predicted to be the larger, specialised frugivorous birds. Bird-dispersed Ficus at Kuala Lompat were all epiphytic species, growing predominantly on large commercial timber trees. Selective logging of lowland forest is therefore predicted to severely deplete the density of bird-dispersed Ficus, especially those species with large figs. Birds particularly dependent on such figs, such as Treron capellei and some of the hornbills, are severely threatened by such practices. Recommendations are made to promote the survival of these vulnerable bird species.

Understanding patterns of heterogeneity and their underlying processes at a variety of scales is the basis of ecology. Heterogeneity in the distribution of the amphipod Corophium volutator was assessed at large (10's to 1000's of m), intermediate (m) and small (cm) scales on the Ythan estuary, where it occurs in abundance, and the role of abiotic features, interspecific interactions and intraspecific interactions and individual behaviour in the maintenance and formation of this heterogeneity investigated. Patchiness at small spatial scales of the order of 0-6 cm was demonstrated in situ in winter and summer populations and under laboratory conditions. The processes underlying this heterogeneity seemed to be related to intraspecific interactions and individual behaviour rather than to interactions with either abiotic features or with other infauna. Conversely, heterogeneity at large and intermediate scales seemed related to patchiness in other biotic features (e.g. macroalgal mats) and a complex of related abiotic features (e.g. topography, sediment grade, inundation period and hydrography) rather than interactions with other infauna or megafaunal predators. Studies on the swimming and crawling mobility of Corophium, suggested data adult males dominate crawling activity, but that this only represents on average 3% of the total population in the sediment. Swimming activity is similarly generally low and dominated by adult males, but periodic peaks occur on night high tides in the neap to spring progression with swimming dominated by juveniles. The relative immobility of adults is likely to maintain heterogeneity at large and intermediate scales within time scales of the same order of magnitude as their life-time, but over longer time-scales heterogeneity at these scales may change with changes in biotic and abiotic features, recruitment and survival of juveniles. Conversely small-scale heterogeneity seems likely to change constantly in position in space through time, although its form may be maintained by intraspecific interactions.

The dispersion of wintering cormorants (Phalacrocorax carbo) was studied in an estuarine habitat in northeast Scotland. Birds were dispersed in mobile clumps both when roosting and when foraging. A cormorant's choice of roosting site appeared to be influenced primarily by the nature of the site, but the use of decoys showed that groups arose on suitable sites by social attraction. There was evidence that the communal roost had survival value as an antipredator strategy. The use of decoys demonstrated that foraging clumps arose through social attraction. Cormorants also followed each other from the communal roost to the foraging grounds. It was concluded that the roost acts as an "information centre" in extending the benefits of social foraging by local enhancement in food-finding. Individual foraging success was not influenced significantly by tidal variations or water-roughness and associated turbidities, but success was higher around midday than at other times of day and most birds foraged around this time. Individual foraging success was not affected by the number of birds foraging but rose significantly with increasing clumping. Adult cormorants were more successful than juveniles and captured larger fish. Foraging in tight groups was thought to be more advantageous to the more inexperienced juvenile birds in reducing the risk of no success compared to foraging other than in groups or alone. The enhanced feeding success of birds in clumps was considered to be a consequence of groups arising in the best foraging areas through local enhancement rather than a result of birds in groups behaving differently from non-group foragers. The dispersion in loose flocks was seen as a strategy for successful exploitation of non-shoaling cryptic prey dispersed in unpredictably located patches.

This thesis examines the relationships between red deer and the natural regeneration of birch woodland in the Scottish Highlands. Red deer may influence regeneration at the germination and establishment phases and these effects are considered separately. All studies were carried out at the Creag Meagaidh National Nature Reserve (NNR), where the red deer population has been reduced by culling since 1986. As a result, deer density is low in comparison to many Highland estates. The potential for regeneration was considered in terms of the germinability of seeds collected within the NNR. The results indicated that the availability of germinable seeds was unlikely to be limiting to regeneration in the near future. The potential germination success of birch at the NNR was investigated experimentally by sowing seeds into gaps created in Calluna- and Molinia-dominated vegetation. Germination was compared between bared-soil gaps (6x6cm, 10x10cm, 25x25cm), hoof-print gaps and undisturbed controls. Germination was improved in bared soil only, but there was no benefit for seedling establishment. In a concurrent experiment, there was little evidence to suggest that red deer at low density created bared-soil gaps and were therefore unlikely to improve the potential for regeneration. Red deer browsing patterns were examined at the NNR and an adjacent estate, with higher deer density. There were strong seasonal patterns in browsing, with peak browsing recorded at both sites in winter, when deer selectively browsed birch in both Calluna- and Molinia-dominated vegetation. There was no evidence of a consistent effect of sapling morphology on the selection of individual saplings by deer. Sapling selection varied with vegetation type and site location and it was suggested that the visibility of saplings to deer may be influenced by site-specific factors, including vegetation structure.

The thesis charts the development of vegetation science from its beginnings. In the first chapter, particular attention is given to the work of Alexander von Humboldt and to the genesis of the idea that vegetation exists in natural units. A tradition of Humboldtian plant geography is traced to the end of the nineteenth century and the birth of self-conscious plant ecology. The second chapter follows the development of different notions of the plant association, and different forms of scientific practice,by F.E. Clements in Nebraska and J. Braun-Blanquet in Montpelier. Chapter Three describes the career of Henry Allan Gleason and follows the development of his individualistic concept of the plant association. Chapter Four examines the work of J.T. Curtis and R.H. Whittaker which revived the individualistic hypothesis and established it as dominant in the English-speaking world. The changing character of the scientific practice of plant ecology is correlated with interests, both internal and external to the discipline. A short coda indicates that debate over the nature of vegetation continues. The thesis is narrative history, written throughout from a social and relativistic perspective.

In this thesis an examination is made of the ecology of the meiofauna in a slow sand filter used for the purification of river derived water for industrial and domestic supply. The physical and operational features of the filter are described in relation to the biology of the organisms inhabiting it. Problems encountered with sampling the meiofauna of such a system are discussed and a criticism of the sampling methods employed is presented. A discussion is made of the uses of total particulate organic carbon as a parameter for characterising the biomass changes in the system. An evaluation of the horizontal and vertical distributions of the meiofauna in the filter is presented. Similar observations are made regarding the distributional heterogeneity of the organic carbon in the system. Special attention is directed to the oligochaetes present. A relationship is determined between length and dry weight and also segment number and dry weight of Enchytraeus buchholzi, the only actively sexually reproducing oligochaete worm present. The segment number - dry weight relationship is exploited to obtain quick estimates of the dry weight of the worm for biomass estimates. Seasonal changes in population abundance of the meiofauna are presented. The need to obtain estimates of parameters not easily measured in an operational filter is discussed. The design and functioning of an experimental small-scale filter is described and criticised. A method is detailed for obtaining interstitial water samples without them coming into contact with air. An account of a micro-Winkler oxygen analysis is given. The results of redox potential measurements and dissolved oxygen analyses, made in the pilot filter, are presented together with a discussion on the insight which these measurements give as far as bacterial activity in the filter is concerned. A discussion is made of the ecology of the meiofauna in slow sand filters and further suggestions for research investigations are made.

Prior to 1973, the St Austell china clay industry discharged fine grade waste into local rivers which carried the waste into Mevagissey Bay, Cornwall. The clay waste, a mica and quartz rich silt buried a marine shell gravel substrate by up to 2 metres. The china clay waste and natural sediments on the surface and subsurface of Mevagissey Bay have been studied and the distribution of live and dead benthic faunas analysed. The benthic faunas presently living in the china clay waste and surrounding shell gravel have been compared to faunas from a similar survey taken during the period of peak discharge (1968) and during the reduction of discharges (1970-1973). Within the bay are four different benthic communities whose distribution reflects the amount and nature of china clay waste present. The only notable changes since the the cessation of dumping being the colonisation by a Tellina tenuis community of a previously azoic muddy substrate near the point of waste discharge into the bay. This research suggests that benthic communities in areas subjected toinert solid pollution will change to communities typical of the grain size of the waste. Each community can be recognised by a distinctive death assemblage although these show little resemblance to the composition of the original living community. Different taphonomic processes control the preservation within each community. Radiographs and microscopic examination of impregnated box core samples reveal the important effect of bioturbation on the orientation and position of shells and shell fragments within the substrate. Since the cessation of china clay waste dumping in 1973, shell debris formed by local benthos has began to transform the soft, fine grade substrate into a shell gravel. It is predicted that it will take within the order of 10,000 years for the substrate to resemble the original shell gravel now lying below the china clay waste.