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No description available.

No description available.

No description available.

This study addresses questions concerning the change from the human exploitation of wild grass species to the cultivation of domesticated cereals. These questions are part of a larger issue concerning the understanding of the human exploitation of grasslands in general. To this end, this project has concentrated on fossil pollen evidence, which is a ubiquitous microfossil but has in the past, had limited success in the morphological differentiation of wild and domesticated Poaceae. The innovative approach applied here has been to develop a means of identifying ancient species based on their genetic code by examining fossil pollen DNA. In order to develop and access a methodology for the extraction of ancient Poaceae pollen DNA it was necessary to find pollen samples that fulfilled the criteria of deriving from cold, stable systems and that were dominated by one species of plant, in order to maximise the probability of the presence of DNA from a particular species which could be targeted with specific primers during amplification. In the absence of any readily available source of Poaceae pollen, lake sites were selected in Norfolk which are dominated by <I>Betula </I>pollen and these form the basis for this study. After considerable testing and development a methodological strategy has been developed for use on ancient pollen. It divides into three main stages: pollen cell lysis; recovery and purification of DNA; amplification of DNA using polymerase chain reaction (PCR) and species specific primers. Results from this innovative study have proved successful for the lysis of ancient pollen without unacceptable damage to the integrity of the DNA. Further work is required to perfect the purification of recovered DNA fragments prior to amplification, but considerable progress has been achieved in methodological processes. The results point to the successful recovery of Poaceae DNA in the future and to the identification and differentiation of wild Poaceae from early domesticated species.

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This research assesses how forest-savanna boundaries have shifted in response to past environmental changes, which is crucial to understanding the present-day vegetation mosaic and the origins of Amazon biodiversity as a whole. Individual plant leaf-wax compounds can be extracted from lake sediments and their isotopic values measured by compound-specific 13C analysis, permitting the evaluation of past changes in the abundance of C3 and C4 graminoids, and thereby clarify ambiguities in the pollen record. In this study, a multiproxy approach, using grass-cuticle assemblages and stable carbon-isotope analyses of total organic carbon, is being applied to a lake-sediment core from Laguna Chaplin (14o28’S, 61o04’W), situated in Noel Kempff Mercado National Park (which straddles a climatic transition zone between Amazonian moist evergreen forest, semi-deciduous forest, and savanna). The δ13C values of TOC ranged from 17% at the LGM to 26% in the late Holocene, suggesting an increased representation of C4 graminoids during glacial times. This finding is consistent with the corresponding glacial-age uncharred fossil cuticle coverages of Salviniaceae as well as pollen assemblages, which are dominated by grasses and palms (Mauritia/Mauritiella) with low levels of rainforest taxa, implying an expansion of seasonally-flooded savannas at the expense of seasonally-flooded forest. Compound-specific 13C analyses of leaf-wax n-alkanes and n-alkanoic acids show a dominance of algal and aquatic macrophytes biomarkers in the last glacial period lending additional support to this inference. The palaeoecological inferences previously made from pollen and bulk carbon-isotope data will be tested using these results, permitting overall conclusions to be drawn at much greater taxonomic resolution.

No description available.

No description available.

No description available.