Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2031-01-01

Fern classification is in a state of flux, the largest area of disagreement being the family Polypodiaceae (Wagner, 1959). This polyphyletic group (Eame, 1936) has been divided by several prominet workers into many families. Ching (1940) recognized thirty-two, Holttum (1947) five, and Copeland (1947) nine families. Munz and Keck (1959) divided the old famliy Polypodiaceae, as represented by the ferns of California, into five families. The classification of Munz and Keck is the most recent treatment in this paper. Historically, classification of the leptosporangiate ferns has been based on the sorus, but the last half century has seen greater use vegetative characters. Problems of phylogenetic relationships can only be solved by the study of a number of features from all aspects of the planet. The more characters considered and evaluated, the more accurate and valuable are the conclusions. This line of reasoning has been pursued fruitfully in other plant groups as exemplifed by Metcalfe (1960) in his work on the anatomy of the monocotyledons. In this work the microscopical characters of the lamina were taken as being of major importance because of eary availability and the fact that one does not have to have the plant in flower before investigations can proceed. Another important reason for studying vegetative characteristics is that they are often preserved in the fossil record. Black (1929), Odell (1932), Florin (1951), and Greguss (1961) have studied cutinized superficial leaf epidermis preserved as fossils. The work of Florin has been particularly important in clarifying the phylogeny of the living conifers The questions of the value of the epidermis in the study of the ferns still remains unsolved problem. Therefore, it is the intention of this paper to explore the possibility of using epidermal charaters as a basis for establishing patterns of morphological and taxonomic significance. Because of their easy availability, the native ferns of California were used for this study.

A Cretaceous fern flora haas been recently discovered near Westwater, Grand County, Utah. Among specimens collected from Westwater are many forms related to extant members of the fern family Matoniaceae. This family was widely distributed geographically throughout most of the Mesozoic Era, and matoniaceous ferns have been collected from several fossil localities in the United States. The Matoniaceae was especially important in the United States during Lower Cretaceous times. Five species, Matonidium brownii Rushforth, Matonidium lanceopennis Rushforth, Matonidium galleyi (Miner) Rushforth, Matonidium americanum Berry em. Rushforth, and Matonidium sp., and one variety, Matonidium brownii var. extenda Rushforth, are considered in the present paper.

Madagascar est une île continentale de l’Océan Indien, au large de l’Afrique. C’est également un point chaud de biodiversité, hébergeant plus de 12 000 espèces de plantes vasculaires, dont plus de 600 espèces de fougères caractérisées par un endémisme dépassant les 45%. L’Afrique continentale n’héberge en comparaison que 800 espèces. Comment peut-on expliquer une telle concentration de biodiversité à Madagascar ? Quelles sont les origines biogéographiques des fougères malgaches ? L’apport de nouvelles données et la littérature préexistante permettent de proposer ici des hypothèses sur l’histoire biogéographique des fougères de Madagascar. Quatre groupes de fougères ont fait l’objet d’une étude biogéographique : les sous-familles de fougères grammitides et blechnoides, les genres Rumohra et Lindsaea-Odontosoria, ainsi qu’un genre de lycophytes, Phlegmariurus, représentant un réplica dans une autre lignée de plantes vasculaires à spores. L’histoire biogéographique des lignées malgaches au sein de ces groupes a été reconstruite, à partir de phylogénies moléculaires mondiales complétées par les espèces malgaches, de datations moléculaires, ainsi que de l’estimation des aires ancestrales.Bien que Madagascar soit d’origine ancienne, gondwanienne, les résultats des analyses biogéographiques montrent que les fougères et les lycophytes auraient colonisé Madagascar après son isolement, durant le Cénozoïque (< 66 Ma), depuis les néotropiques (Amérique du Sud) l’Afrique et l’Asie tropicale (au sens large, incluant l’Asie continentale et le sud-est asiatique jusqu’en Australasie). En particulier, de nombreuses dispersions ont été observées à partir du Miocène (< 23 Ma). Ces résultats seraient expliqués par une combinaison d’événements au Cénozoïque (formation des forêts tropicales humides Malgaches, formation de courants éoliens permettant la dispersion par spores) et des préférences écologiques des fougères et des lycophytes pour les forêts tropicales humides d’altitude, s’étant formées à partir du Miocène dans les régions sources. / Madagascar is a continental island in the Indian Ocean, near African coasts. It is also a biodiversity hotspot, comprising more than 12,000 species of vascular plants and including more than 600 fern species with an endemism reaching the 45%. Comparatively, continental Africa comprises only 800 species. How can such a diversity be explained in Madagascar? What are the biogeographical origins of the Malagasy ferns? Thanks to new data combined to the literature, hypotheses on the biogeographical history of Malagasy ferns are here proposed.Four fern taxa were newly investigated: grammitid and blechnoid subfamilies, Rumohra and Lindsaea-Odontosoria, as well as Phlegmariurus, a genus of lycophytes considered as a phylogenetic replicate in another vascular spore-bearing plant lineage. The biogeographical history of the Malagasy lineages was inferred, based on worldwide molecular phylogenies completed by Malagasy species, molecular dating and ancestral area estimates.Despite its Gondwanian origin, ferns and lycophytes would have colonized Madagascar after its isolation, during the Cenozoic (< 66 Ma), from the Neotropics (South America), Africa and tropical Asia s.l. (meaning from continental Asia to Southeast Asia and Australasia). Dispersal events were especially inferred from the Miocene (< 23 Ma). These results could be explained by the combination of events during the Cenozoic (establishment of the Malagasy rainforests, onset of wind currents allowing spore dispersal) and ecological preferences of ferns and lycophytes for elevated tropical rainforests that have established from the Miocene in the source regions.

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Tree ferns are listed as endangered species under Mexican law and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Despite this status, tree ferns are currently being harvested by rural communities, and sold in the form of handicrafts, traditional medicines, and household ornaments In the state of Veracruz, some authors argue that the harvesting of tree fern caudexes (trunks) to obtain a material made out of the fern’s adventitious roots called maquique poses a major threat to tree fern conservation. This thesis systematically explores the effect of harvesting activities on the distribution of tree fern species in the tropical montane cloud forest’s fragmented landscape using vegetative regeneration as a proxy for maquique harvesting. The study was conducted in El Zapotal in the municipality of Acajete and El Riscal in the municipality of Coatepec, two small communities with different land use histories. A census was performed at each site to georeference and document all tree fern individuals, including information on diameter, height and presence/absence of vegetative regenerations due to maquique harvesting per individual tree fern. Four species were present in the study: Alsophila firma, A. tryoniana, Cyathea bicrenata, and C. fulva. ArcGIS Desktop was used to calculate distances from individual tree ferns to trails and rivers, which were regarded as points of access for maquique harvesters. These data were used to infer how and whether maquique affects the distribution and abundance of tree fern species at the two studied sites. This study reports for the first time different forms of vegetative regenerations in Mexican tree fern species such as the resprouting of multiple branches from a single tree fern trunk and also documents different forms of harvesting like the “C cut”. Contrary to common conservation arguments, the study shows that tree ferns can continue to thrive even after a severe environmental modification, such as forest clearing and the establishment of tree plantations. Other results suggest that maquique harvesters operating clandestinely are more likely to target tree ferns with maquique closer to points of access (trails or rivers) rather than according to size. In the long run, this pattern of tree fern harvesting could modify the distribution of tree ferns as they are displaced from areas closer to human access, despite the ability of some tree fern species to regenerate in highly disturbed environments. The discovery of tree fern regenerative properties offers potential for the management of certain tree fern species as umbrella species for conservation in central Veracruz. It suggests that maquique harvesting might be sustainable given careful management and government regulation based on scientific data. / text

Doctor of Philosophy(PhD) / Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments.

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Bracken (Pteridium aquilinum) is a cosmopolitan species of fern which possesses extrafloral nectaries. A survey of the arthropod fauna associated with the plant throughout its range in South Africa identified the most widespread and damaging bracken herbivores and those species most likely to be influenced by ants visiting the extrafloral nectaries. Seventeen herbivorous arthropods were found to be definitely feeding on bracken and a further thirteen species with a less certain status were recorded. In addition, several species of ants were observed on the fronds and feeding at the extrafloral nectarie. On the basis of their widespread distribution and abundance, four bracken herbivores emerged as being particularly detrimental to the plant in South Africa. They were an eriophyid gall mite, a leafhopper and two moths. The biology of the two lepidopterans, Appana cinisigna and Panotima sp., suggested that they were potentially vulnerable to ants at various stages of their life histories. Laboratory experiments were undertaken to observe ant-lepidopteran interactions under controlled conditions. The ant Crematogaster peringueyi rapidly removed exposed A. cini igna eggs, but did not appear to regard Panotima eggs as food items. Small instar larvae of both species proved vulnerable, but the larger larvae appeared capable of escaping ant predation. Ant exclusion experiments in the field, using natural and artificially augmented ant densities, were carried out at two sites near Grahamstown. The dominant ant species was C. peringueyi. Neither the numbers of lepidopterans nor levels of herbivory were significantly reduced by the presence of ants . Despite the implications of the laboratory tests, the results of these field experiments did not support the hypothesis that ants which visit bracken extrafloral nectaries benefit the plant. Ant-bracken field studies on other continents also reported no significant ant-related effects, though marginal reductions in the abundance of certain herbivores have been noted at one site in the U.K. Since ant protection does not appear to be an inevitable consequence of having extrafloral nectaries, their value to bracken is in some doubt. The most likely situation where effective protection will occur is when high densities of vulnerable herbivores are preyed upon by large numbers of aggressive ants. However, even under these conditions, enhancement of plant fitness is not inevitable. This raises the question of why extrafloral nectaries have been retained in a plant that is as successful and widespread as bracken.

The validity of niche-assembly rules in explaining community structure is revisited by testing for ecological separation among ferns. An intensive, fine-scale survey of fern abundance and environmental variation was done in 1-ha of old-growth forest. Three methods of detecting niche segregation (canonical correspondence analysis, detrended correspondence analysis and GIS mapping) suggested that most fern species at the site are distributed according to distinct environmental preferences. The most important gradients separating fern species are first, the amount of soil moisture and second, soil nitrate concentration. Contrary to other findings, pH had little influence on controlling fern distribution. Spatial autocorrelation, detected by partialled ordinations, obscured the presence of niche partitioning. As well, sampling grain changed the apparent location of some species on environmental gradients and their ecological similarity to other species. Finer-scaled environmental heterogeneity or dispersal-mediated processes may account for the unexplained variation in fern species abundance of this site.