No description available.

This study examines contemporary vegetation, pollen taphonomy and Holocene vegetation history across east-west trending environmental transects in the southern Outer Hebridean islands of South Uist and Barra. The pollen depositionalc haracteristicso f sixteenp lant communities are described and modern pollen deposition is found to reflect the distribution of major vegetation types on the islands. The history of Holocene vegetation is investigated at a number of sites which include exposed west coast inter-tidal peat deposits, wooded loch islands and pre-peat soils associated with archaeological features. These studies indicate that Holocene vegetation development followed a pattern typical for the region at similar latitudes. The early post-glacial vegetation mosaic of Empetrum heath, herb-rich grassland and dwarf shrub communities was progressivly altered by the subsequent establishment of predominantly deciduous woodlands. The pollen diagrams record an ordered sequence of tree migration to the islands in which Betula then Corylus were the first colonists followed later by Ulmus, Quercus, Pinus Alnus and Fraxinus. The scales of analysis employed in the study indicate that very local' pollen deposition is a characteristic of the islands' micro-fossil record - a feature which could be exploited in further archaeologically related studies. Woodland appears to have persisted in sheltered locations until c. 5,000 B. P. A gradual reduction of woodland from c. 5,000 B. P. was accompanied by an expansion of the herb-rich grassland and blanket bog communitiues which had been present on the islands from the early Holocene After c 4,000 B.P .w oodland decline accelerateda nd the grasslanda nd blanket peat communities increased to attain their present dominance in the islands vegetation. The vegetation changes recorded in the pollen diagrams are attributed to a combination of factors changing environmental conditions - such as the pedological effects of Holocene climatic conditions, sea level rise and human impacts. There is no archaeological evidence for mesolithic occupation of the islands, however at a point in the 'early' Holocene a brief episode of fluctuating woodland disturbance, charcoal and 'cereal type' pollen is noted at one east coast site, Loch Hellisdale. This data contributes to an increasing body of information which suggests some mesolithic presence along the eastern coast of South Uist.

The application of numerical techniques within palaeoentomology has been sporadic and of a largely simplistic nature. In particular, the assessment of faunal similarity has relied mainly upon subjective value judgements; similarly, the reconstruction of past climates using fossil Coleoptera has been undertaken with only a limited application of numerical methods. This thesis presents a computational approach to these problems. Although the intrinsic properties of palaeoentomological sample units impose limitations on the validity of a statistical analysis of faunal similarity, the use of such techniques is fully justifiable. Several methods have been tested with a wide range of data, using intuitive interpretations as reference standards. Binary data, in conjunction with a limited combination of clustering techniques and resemblance coefficients, produce results which compare favourably with the traditional assessments; numeric data and Principal Components Analysis are useful in difficult analytical situations and / or when particularly complex questions are being asked. To enable palaeoclimatic reconstructions to be produced quickly and accurately a computer package of Fortran programs has been written and implemented. By representing the geographical range of a beetle on climatic axes it is possible to derive estimates of the past thermal climate from an assemblage of fossil beetles. Using the Mutual Climatic Range Reconstruction Package the thermal climate of Britain during the Late Quaternary has been examined in detail. The pattern correlates with that derived from ocean care data, being characterised by abrupt changes between contrasting climatic states. The climatic reconstruction methodology has been inverted to provide a means whereby potential coleopteran faunas can be derived for particular thermal climates. In the context of the origin of the invertebrate faunas of the N. Atlantic Islands, the results of the Pest program provide support for a glacial tabula rasa followed by immigration via ice rafting at c. 10,000 B. P., as opposed to the alternative hypothesis of glacial survival in refugia.

No description available.

No description available.

No description available.

The marine microfossils of planktic foraminifers are widely used for investigating palaeoceanographic and palaeoclimatic conditions. The objective of this project was to investigate genotypic variation within planktic foraminiferal morphospecies and the spatial distribution of genotypes in the subpolar, transitional and subtropical North Atlantic. Foraminiferal genomic DNA was extracted and the ~1000 base pair 3' terminal region of the small subunit ribosomal RNA gene was amplified using the polymerase chain reaction. Using distance-based molecular phylogenetic analysis, a neighbour-joining phylogeny was reconstructed based on 31 planktic and15 benthic previously sequenced foraminifera and extended to include 15 genotype sequences obtained from the North Atlantic during this study. Bulk plankton samples were collected for preliminary examination of genotype/morphotype relationships. The molecular phylogeny is largely consistent with the foraminiferal fossil record. It supports the suggestion that the origins of planktic foraminifers are polyphyletic, as the spinose planktic foraminifers cluster separately from the non-spinose planktic foraminifers within the phylogeny. Brachn length variation within the planktic cluster reflects large differences in evolution rate between morphospecies. Within the North Atlantic, genotypic variation has been identified within the morphospecies, <i>Globigerina bulloides, Turborotalita quinqueloba, Globigerinella siphonifera, Globigerinella calida, Globigerinoides ruber</i> and <i>Neogloboquadrina pachyderma.</i> The distribution of genotypes is complex, and it has been found that genotypes, representing a single morphospecies, often co-exist within the water column. This could be indicative of cryptic speciation, suggesting that North Atlantic planktic foraminiferal diversity is much higher than fossil record interpretations have indicated. The genotypes within <i>G. bulloides, G. siphonifera, G. calida</i> and <i>T. quinqueloba</i> have different geographic distributions within the North Atlantic. It is apparent that <i>G. bulloides </i>Types IIa and IIb and <i>G. siphonifera </i>Types IIa and IIb have extensive distributions suggesting that they are more generalist in adaptation, and tolerant to a wide range of oceanic conditions.

No description available.

No description available.

The anatomy, morphology and distribution of calcareous encrusting organisms (crustose coralline algae, bryozoans, foraminiferans, serpulid worms and corals) from the Recent reefs of Barbados have been related to both physical environmental and biotic factors within the marine environment in order to produce a model of encruster ecology. This model has been used in the interpretation of the conditions of growth of uplifted Pleistocene reefs on the island. Patterns of encruster distribution are based on measurements of encruster size and/or density of colonisation of both natural (reef) and artificial (glass, brick, wood, perspex anti concrete) substrates. For each encruster group, distribution can be related to the influence of specific environmental factors on the settlement and growth of developing individuals. The specific way in which this mechanism operates has been investigated for each encruster group. The differing ability of the various encrusters to withstand and to utilise variations in the physical and biotic environments results in a zonation of species on the Recent reefs. This zonation is summarised in the form of a model of encruster distribution which lists the dominant encrusters found within each habitat (as defined by depth, degree of illumination and hydrodynamic exposure) on the reef. This distribution model is used in the investigation of the palaeoecology of the Pleistocene reefs of Barbados where encrusters have documented not only the environmental conditions prevailing at the time of growth of the reef framework, but, by continued growth, have recorded the entire preservational history of the various framework components after their death and prior to burial sediment. Using encrusters, a detailed picture of Pleistocene reef ecology has been constructed. Finally, the various methods of crust growth are outlined, along with a discussion of the role of encrusters in the construction of the reef and a description of the way in which other processes interract with and affect crust growth and the products which result.