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Durvillaea, a kelp genus occurring only in the Southern Hemisphere, presents an ideal system for studies of marine connectivity and postglacial recolonisation. Durvillaea contains five currently-recognised species, four of which are non-buoyant. Whereas all non-buoyant species are restricted to the south-western Pacific, the sole buoyant species (D. antarctica) has a far wider, circumpolar distribution, strongly suggesting that long-distance dispersal in D. antarctica is achieved by rafting. This contrast in predicted dispersal ability among Durvillaea species provides an opportunity for natural phylogeographic comparisons, thereby assessing the effectiveness of rafting as a long-distance dispersal mechanism. Additionally, the inability of D. antarctica to survive in ice-affected areas, combined with its broad distribution, make it an ideal candidate for studies of postglacial recolonisation. Phylogenetic and biogeographic relationships within Durvillaea were here assessed using sequence data from mitochondrial (COI), chloroplast (rbcL) and nuclear (18S) DNA. Genetic data were obtained from more than 500 specimens, including representatives from across the geographic range of each recognised species of Durvillaea. Mitochondrial data for Durvillaea were found to be highly phylogenetically informative, with 117 variable sites observed over a 629 bp fragment of COI. Chloroplast and nuclear markers, on the other hand, showed less variation than COI, but nonetheless contributed useful phylogenetic information. Phylogenetic analyses were performed using both Maximum Likelihood and Bayesian approaches. Contrasting patterns of genetic diversity were observed across the range of D. potatorum in Australia, with genetic homogeneity throughout western sites versus relatively high levels of diversity in eastern populations. Based on these results, I hypothesise that D. potatorum recolonised much of the western part of its range postglacially, perhaps being entirely eliminated from western Tasmania during the last glacial period by altered oceanographic systems. Additionally, 'western' and 'eastern' D. potatorum haplotypes formed deeply-divergent clades, likely reflecting geographic isolation on either side of the Bassian Isthmus during Pleistocene marine regressions. Substantial genetic diversity was observed across the range of the circumpolar species D. antarctica. Within New Zealand, phylogenetic and morphological analyses of D. antarctica indicate that two morphotypes ('cape' and 'thonged' forms) likely represent reproductively isolated species, with the 'cape' lineage apparently restricted to southern New Zealand. Whereas the 'cape' lineage showed little genetic variation throughout its range, the 'thonged' lineage exhibited marked phylogeographic structure, with high genetic diversity and a clear north - south genetic disjunction delineated by the Canterbury Bight. On a broader, circumpolar scale, D. antarctica showed contrasting patterns of genetic diversity, with high levels of variation in low-latitude regions (e.g., continental coasts of New Zealand and Chile), versus near-homogeneity at high, subantarctic latitudes. These phylogeographic contrasts strongly suggest that D. antarctica recolonised much of the subantarctic region only recently, most plausibly following extirpation by ice scour at the Last Glacial Maximum (LGM). Locations of putative recolonised islands relative to 'refugial' areas indicate that Antarctic sea ice was likely more extensive at the LGM than previous studies have suggested. Latitudinal contrasts in genetic diversity were also observed among Chilean populations of D. antarctica, with a single mitochondrial haplotype detected throughout Chilean Patagonia versus high diversity in central Chile (32�-42�S). The Patagonian populations appear to have recolonised the region postglacially, following recession of the Patagonian Ice Sheet after the LGM. These populations show transoceanic ancestry, with a closer relationship to populations in the subantarctic and southern New Zealand regions than to those in central Chile. Substantial phylogeographic structure was evident across small spatial scales in central Chile, and the correspondence of major genetic disjunctions among central Chilean sites with the presence of long stretches of unsuitable substrate (beaches) strongly suggests that habitat discontinuity drives genetic isolation in this dispersive species. Broad-scale molecular phylogenetic analyses indicate that the current taxonomy of Durvillaea species requires substantial revision. Previously-recognised 'morphotypes' of Durvillaea (of D. potatorum in Australia, and D. antarctica in New Zealand), for example, were here found to be genetically distinct, likely representing reproductively-isolated species. This phylogeographic research on Durvillaea kelp sheds new light on the historical impacts of climate change on Southern Hemisphere marine environments, and on the processes driving evolution in a marine macroalga.

Durvillaea, a kelp genus occurring only in the Southern Hemisphere, presents an ideal system for studies of marine connectivity and postglacial recolonisation. Durvillaea contains five currently-recognised species, four of which are non-buoyant. Whereas all non-buoyant species are restricted to the south-western Pacific, the sole buoyant species (D. antarctica) has a far wider, circumpolar distribution, strongly suggesting that long-distance dispersal in D. antarctica is achieved by rafting. This contrast in predicted dispersal ability among Durvillaea species provides an opportunity for natural phylogeographic comparisons, thereby assessing the effectiveness of rafting as a long-distance dispersal mechanism. Additionally, the inability of D. antarctica to survive in ice-affected areas, combined with its broad distribution, make it an ideal candidate for studies of postglacial recolonisation. Phylogenetic and biogeographic relationships within Durvillaea were here assessed using sequence data from mitochondrial (COI), chloroplast (rbcL) and nuclear (18S) DNA. Genetic data were obtained from more than 500 specimens, including representatives from across the geographic range of each recognised species of Durvillaea. Mitochondrial data for Durvillaea were found to be highly phylogenetically informative, with 117 variable sites observed over a 629 bp fragment of COI. Chloroplast and nuclear markers, on the other hand, showed less variation than COI, but nonetheless contributed useful phylogenetic information. Phylogenetic analyses were performed using both Maximum Likelihood and Bayesian approaches. Contrasting patterns of genetic diversity were observed across the range of D. potatorum in Australia, with genetic homogeneity throughout western sites versus relatively high levels of diversity in eastern populations. Based on these results, I hypothesise that D. potatorum recolonised much of the western part of its range postglacially, perhaps being entirely eliminated from western Tasmania during the last glacial period by altered oceanographic systems. Additionally, 'western' and 'eastern' D. potatorum haplotypes formed deeply-divergent clades, likely reflecting geographic isolation on either side of the Bassian Isthmus during Pleistocene marine regressions. Substantial genetic diversity was observed across the range of the circumpolar species D. antarctica. Within New Zealand, phylogenetic and morphological analyses of D. antarctica indicate that two morphotypes ('cape' and 'thonged' forms) likely represent reproductively isolated species, with the 'cape' lineage apparently restricted to southern New Zealand. Whereas the 'cape' lineage showed little genetic variation throughout its range, the 'thonged' lineage exhibited marked phylogeographic structure, with high genetic diversity and a clear north - south genetic disjunction delineated by the Canterbury Bight. On a broader, circumpolar scale, D. antarctica showed contrasting patterns of genetic diversity, with high levels of variation in low-latitude regions (e.g., continental coasts of New Zealand and Chile), versus near-homogeneity at high, subantarctic latitudes. These phylogeographic contrasts strongly suggest that D. antarctica recolonised much of the subantarctic region only recently, most plausibly following extirpation by ice scour at the Last Glacial Maximum (LGM). Locations of putative recolonised islands relative to 'refugial' areas indicate that Antarctic sea ice was likely more extensive at the LGM than previous studies have suggested. Latitudinal contrasts in genetic diversity were also observed among Chilean populations of D. antarctica, with a single mitochondrial haplotype detected throughout Chilean Patagonia versus high diversity in central Chile (32�-42�S). The Patagonian populations appear to have recolonised the region postglacially, following recession of the Patagonian Ice Sheet after the LGM. These populations show transoceanic ancestry, with a closer relationship to populations in the subantarctic and southern New Zealand regions than to those in central Chile. Substantial phylogeographic structure was evident across small spatial scales in central Chile, and the correspondence of major genetic disjunctions among central Chilean sites with the presence of long stretches of unsuitable substrate (beaches) strongly suggests that habitat discontinuity drives genetic isolation in this dispersive species. Broad-scale molecular phylogenetic analyses indicate that the current taxonomy of Durvillaea species requires substantial revision. Previously-recognised 'morphotypes' of Durvillaea (of D. potatorum in Australia, and D. antarctica in New Zealand), for example, were here found to be genetically distinct, likely representing reproductively-isolated species. This phylogeographic research on Durvillaea kelp sheds new light on the historical impacts of climate change on Southern Hemisphere marine environments, and on the processes driving evolution in a marine macroalga.

Beach‐cast kelp (principally Laminaria spp.), known as macroalgal wrack, has been suggested as a feedstock for biofuel. However, to be extracted sustainably it is necessary to understand its ecological role and predict the impacts of its removal. Field‐based observations combined with food web modelling were used to predict the ecosystem effects of removing wrack from beaches of the Uists, western Scotland. Beaches with wrack were associated with enriched benthic infauna (polychaetes) on the lower shore, and wrack mounds supported abundant macroinvertebrates (mainly Diptera larvae and oligochaetes); with some of the highest biomasses reported globally for beaches. These fauna are valuable prey to shorebirds, as demonstrated by a strong positive relationship (R2 = 0.82) between wader abundances and the percentage cover of wrack on beaches. Inshore, drifting macroalgae was associated with elevated abundances of detritivorous hyperbenthic fauna (mysids, isopods and gammarid amphipods). In addition, the volume of drifting macroalgae inshore was a significant predictor (along with physical beach characteristics) for the abundance of decapods and fish. Food web models and network analysis indicated that beaches which accumulate wrack had a greater diversity of trophic links and more functional redundancy, making their food webs more resilient to perturbations. Such perturbations may include stressors induced by climate change, such as increased erosion of sediments during storms, elevated atmospheric and sea surface temperatures and elevated CO2 concentrations. Model simulations of wrack harvesting predicted an immediate decline in primary consumers in direct proportion to the quantity of wrack removed, and a slow decline in shorebirds in response to reduced prey. Primary consumers were predicted to recover to their pre‐harvest biomasses within 1 to 2 years regardless of harvesting intensity, but recovery times for shorebirds were an order of magnitude longer, and increased with harvesting intensity. Harvesting more than 50% wrack predicted a ‘collapse’ in wader populations within 25 years, and recovery times of 45‐60 years were estimated if >70% wrack was removed. The findings of this thesis suggest wrack provides essential food and shelter to coastal fauna, and its large‐scale removal would have significant negative impacts to the ecosystem functioning.

by Fung Yin Lee, Annie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 181-189). / ABSTRACT --- p.i / LIST OF ABBREVIATIONS --- p.iv / ACKNOWLEDGEMENT --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.ix / INTRODUCTION --- p.1 / LITERATURE REVIEW --- p.4 / Chapter I. --- A. Arterial pressure --- p.4 / Chapter B. --- Regulation of arterial pressure --- p.7 / Chapter II. --- Hypertension --- p.14 / Chapter III. --- Treatment of hypertension --- p.29 / Chapter IV. --- Plants and their effects on blood pressure --- p.48 / Chapter V. --- Characteristics of the three plants being studied --- p.50 / MATERIALS AND METHODS --- p.55 / Chapter A. --- Preparative procedures --- p.55 / Chapter 1. --- Preparation of plant extracts --- p.55 / Chapter 2. --- Animal preparation for invivo blood pressure measurement --- p.56 / Chapter 3. --- Preparation of right atria for in vitro studies --- p.56 / Chapter 4. --- Preparation of artery strips for in vitro studies --- p.57 / Chapter 5. --- Preparation for diuretic studies --- p.58 / Chapter B. --- Experiments done --- p.60 / Chapter 1. --- Cumulative dose response of individual plant extract --- p.60 / Chapter 2. --- Combination of plant extracts --- p.60 / Chapter 3. --- Pharmacological antagonists studies --- p.64 / Chapter a. --- Autonomic ganglion transmission --- p.64 / Chapter b. --- Alpha adrenergic activity --- p.64 / Chapter c. --- Beta adrenergic activity --- p.65 / Chapter d. --- Cholinergic activity --- p.65 / Chapter e. --- Histaminergic activity --- p.65 / Chapter f. --- Serotoninergic activity --- p.65 / Chapter 4. --- Urinary and sodium excretionin water loaded rats --- p.66 / Chapter 5. --- Studies on chronotropic and inotropic effects on isolated right atrium --- p.66 / Chapter a. --- Effect of individual plant extract --- p.66 / Chapter b. --- Effect of combination of plant extracts --- p.66 / Chapter 6. --- Effect of plant extract on contractile responses of rat tail artery strips --- p.70 / Chapter a. --- Effect of individual plant extract --- p.70 / Chapter b. --- Effect of combination of plant extracts --- p.70 / Chapter 7. --- Effect of acute oral feeding of plant extracts on blood pressure of rats --- p.71 / Chapter C. --- Statistics --- p.71 / RESULTS / Chapter A. --- Preparation of plant extracts --- p.72 / Chapter B. --- Effect of plant extracts on blood pressure changes --- p.72 / Chapter 1. --- Individual plant extract --- p.72 / Chapter 2. --- Combination of two plant extracts --- p.73 / Chapter 3. --- Combination of three plant extracts --- p.76 / Chapter C. --- Pharmacological antagonist studies --- p.79 / Chapter 1. --- Autonomic ganglion transmission --- p.79 / Chapter 2. --- Alpha adrenergic activity --- p.79 / Chapter 3. --- Beta adrenergic activity --- p.81 / Chapter 4. --- Cholinergic activity --- p.82 / Chapter 5. --- Histaminergic activity --- p.83 / Chapter 6. --- Serotoninergic activity --- p.84 / Chapter D. --- Urinary and sodium excretion in water loaded rats --- p.85 / Chapter E. --- Chronotropic and inotropic studies of isolated right atrium --- p.88 / Chapter 1. --- Effect of individual plant extract --- p.88 / Chapter 2. --- Effect of combination of plant extracts --- p.89 / Chapter F. --- Effect of plant extracts on contractile responses of rat tail artery strips --- p.101 / Chapter G. --- Effect of acute oral feeding of plant extracts on MAP of rats --- p.102 / DISCUSSION --- p.156 / Chapter A. --- Comment on preparation of plant extracts --- p.156 / Chapter B. --- The hypotensive effects of the plant extracts --- p.157 / Chapter C. --- The mechanism of action --- p.159 / Chapter D. --- The renal effect of plant extracts --- p.161 / Chapter E. --- The interaction of the hypotensive effect of plant extracts --- p.164 / Chapter F. --- In vitro studies --- p.167 / Chapter G. --- The oral effect of the plant extracts --- p.174 / SUMMARY --- p.176 / CONCLUSION --- p.179 / REFERENCES --- p.181 / APPENDIX --- p.190 / "Appendix I To study the hypotensive effects of trypsin treated green bean, rue and kelp" --- p.191 / "Appendix II To study the hypotensive effects of ether treated green bean, rue and kelp" --- p.194

Fung Yin Lee, Annie. / "January 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 132-146). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.