Thesis (M.S.)--University of Wisconsin--Madison, 1957. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [40-45]).

Thesis (B.S. in Ag.)--Cornell University, 1907.

The present study consists of a taxonomic revision of the New World species of Sesbania (Papilionoideae, Robinieae) and taxonomic studies on the unifoliolate species of Lupinus (Papilionoideae, Genisteae) in Brazil. The genus Sesbania in the New World is here recognised as comprised of the subgenera Sesbania (with three native and three introduced species), Daubentonia (with five species) and Agati (one species, introduced). As part of the taxonomic revision of Sesbania, a survey on chromosome number and studies on pollen and seed morphology are presented. In an outline treatment of the genus Lupinus in Brazil the problems associated with the ca. 16 multifoliolate species are reviewed. The unifoliolate species have been studied in detail and 13 species are recognised. A taxonomic account of the unifoliolate species with key, descriptions and illustrations and specimen citations is presented. A SEM survey of pollen grains and testa of Lupinus, with particular emphasis on the Brazilian unifoliolate species accompanies this study.

The construction of a chloropast DNA restriction enzyme site based phylogeny for the genus Acacia and several related genera was completed. This investigation was initiated due to a perceived need for an independent viewpoint on the phylogeny of the genus. The results of this analysis challenge several previous attempts at classification of the genus using morphological characters. The cpDNA data suggest that subgenus Acacia and subgenus Aculeiferum are closely related. The third subgenus of Acacia, subgenus Phyilodineae, is probably unrelated to either of the other two subgenera. Instead it appears to be closely related to taxa in the Ingeae, a sister tribe to the Acacieae. This analysis also suggests that Faidherbia albida is basal to the Ingeae. The interspecific relationships of taxa within each of the subgenera of Acacia were also partly resolved. Within subgenus Acacia the African accessions studied could not be resolved due to a lack of variation. The American accessions of subgenus Acacia were resolved, and appear to confirm groupings within these taxa suggested by morphological analyses. Within subgenus Aculeiferum the interspecific relationships were less clear, and little support was given to the sections proposed by Vassal (1972), with the exception of section Filicinae, which appears to be monophyletic, the relationships of taxa within subgenus Aculeiferum in regard to their geographical origin suggest that subgenus Aculeiferum was quite well differentiated when Gondwanaland fragmented. The results of an investigation into the putative hybrid A.laeta appear to confirm earlier suggestions that it is a hybrid between A.Senegal and A.mellifera. The appearance of non-additive hybrid phenotypes in the ribosomal nuclear DNA studied prevented an unequivocal determination of the parents of A.laeta. On the basis of the cpDNA characters it appears that A.mellifera is always the maternal parent. The relationships of the subspecies of A.tortilis using RAPD techniques, revealed an interesting divide between North African and South African accessions. The taxa studied appeared to be grouped primarily according to their geographical location, the subspecific designation appearing to be of secondary importance. The divide between the accessions appears to be the boundary of one of the phytogeographical regions of Wickens (1976), corresponding approximately to the Kenyan-Tanzanian border. The physical or biological basis for this boundary is unknown. The investigation also proved the utility of the RAPD technique for investigations of this nature.

The pantropical genus Caesalpinia sensu lato contains about 120 to 130 species, of which 70 to 75% are neotropical. The genus belongs in the Caesalpinia group (Caesalpinioideae: Caesalpinieae) of Polhill and Raven (1981). A morphological cladistic analysis of the Caesalpinia group demonstrates that the traditional circumscription of the genus Caesalpinia is polyphyletic: some species are more closely related to other genera in the group than to each other. The Poincianella and Erythrostemon elements of Caesalpinia sensu lato, selected for more detailed study, have been united and the resulting, strictly neotropical group, has been expanded to include several South American taxa previously placed in other infrageneric groups of Caesalpinia sensu lato. The Poincianella- Erythrostemon group has been revised and 56 taxa in 47 species are currently recognised. These have a geographical range from south eastern U.S.A. to southern Chile and most species have a predilection for semi arid areas. A key to species identification, full descriptions and specimen citations are provided; most species are illustrated and all are mapped. One new species, Caesalpinia coccinea, discovered during this research, has already been published (Lewis and Contreras, 1994). Eight other new taxa and two new combinations presented here are to be effectively published in a future volume of Kew Bulletin. Sections on morphology, seed chemistry, biogeography and floral biology discuss the relationships between the Poincianella-Erythrostemon group and other infrageneric groups of Caesalpinia s.l. A survey of floral secretory structures in Caesalpinia sensu lato is presented in Appendix 1 and an account of the sexual systems of two species of the Poincianella-Erythrostemon group in Appendix 2.

M.Sc. (Botany) / Seed dormancy in Cyclopia spp. (Fabaceae) was investigated using seed from the seeder C. subternata and the resprouter C. intermedia obtained from the Southern Cape region. Seed of both species exhibited seed coat imposed dormancy which could be broken by scarification of the seed coat. However, in addition to an impermeable seed coat, seeds from C. intermedia also exhibit an embryo imposed dormancy which could be broken by cold treatment. Treatment of the seeds with gibberellic acid (GA3 ) , cytokinin (BA) and ethylene could be substituted for the cold treatment. The ethylene sensitivity of the seeds could be enhanced with short-chain saturated fatty acids (octanoic acid) which further stimulated germination. The effect of plant-derived smoke was also investigated and it appears that, in combination, ethylene and short-chain saturated fatty acids present in the smoke stimulate germination of the seeds. Treatment of the seeds with norbornadiene (NBD) before the above treatments resulted in the inhibition of germination, indicating that germination of the seeds of Cyclopia spp. is primarily controlled by the action of ethylene. The interaction between cold treatment, GA3 , BA and ethylene during germination of the seeds will be discussed.

Fabaceae is the second most speciose plant family in the Core Cape Subregion (CCR) of South Africa, a Mediterranean type ecosystem, with mostly nutrient-poor soils. A majority of the legumes occurring in this region belong to the predominantly nitrogen-fixing subfamily Papilionoideae and they employ a variety of strategies for nutrient acquisition. However, legumes are neither uniformly nor randomly distributed in the CCR landscape. Instead, distinct legume species assemblages tend to occupy particular habitats within the landscape. The drivers of this distribution pattern are yet to be determined. In this thesis, it was hypothesized that edaphic factors (soil chemical and physical characteristics) and the distribution of rhizobia have influenced legume distributions in the CCR landscape. The influence of edaphic factors on the distribution of legume species assemblages in the Cape Peninsula (a microcosm of the CCR) is the subject of the second chapter of the thesis. It was hypothesized that the composition of legume species assemblages is correlated with soil physical and chemical properties and that the interaction of Phosphorus (P) and the three cations that often bind P, i.e. Aluminium, Calcium and Iron, making it unavailable to plants, drive legume species assemblages in the landscape. Soils from 27 legume sites, spanning all major soil types of the Cape Peninsula, were analysed for 31 chemical and physical properties. Surveys of legume species present at each site were conducted to generate a presence/absence matrix. Canonical correspondence analysis was used to test for a correlation between legume species composition and edaphic factors. The strength of the association between legume species composition and site groupings based on edaphic properties was assessed using indicator species analysis. A significant correlation between edaphic factors and species composition was found and the key edaphic parameters driving the relationship were clay content, iron (Fe), potassium (K), sulphur (S) and zinc (Zn). Indicator species, characteristic of the various edaphic habitats were also identified. These findings indicate that distinct edaphic habitats are occupied by discrete legume species assemblages, implying a significant influence of edaphic factors on the legume distributions. Chapter three of the thesis sought to determine if the ecological parameters; altitude, pH and soil type influence the distribution of the two main rhizobial genera (Burkholderia and Mesorhizobium) that nodulate various legumes of the CCR, and to determine the diversity and phylogenetic position of rhizobia that associate with the narrowly distributed and rare Indigofera superba in the CCR. The first objective was pursued through molecular characterisation of rhizobial strains isolated from nodules of legume species collected in the field across the Cape Peninsula. DNA sequences for 16S rRNA, recA and nodA were combined with data from a previous study that sampled broadly within the CCR and phylogenetic analyses were conducted. Tests for phylogenetic signals for the three ecological parameters were conducted, using the D statistic for soil type and Pagel’s λ for altitude and pH. These analyses were used to test the hypothesis that closely related species occupy similar habitats with respect to each of the three ecological parameters. For the study of rhizobial symbionts of Indigofera superba, field nodules were sampled from multiple populations across its distribution range and a phylogeny of its symbionts was reconstructed in a matrix that included symbionts of diverse legumes from different habitats within the CCR. The results showed that Burkholderia is restricted to acidic habitats, while Mesorhizobium occurs in both acidic and alkaline habitats. Additionally, both rhizobial genera showed significant phylogenetic clustering for pH and most soil types. However, none of the genera showed a phylogenetic structure with respect to altitude. These findings indicate that pH and soil type influence the distribution of rhizobia in the CCR. Implications of these findings for the distribution of legumes in the landscape are discussed. For the narrowly distributed I. superba, the results showed that it associates with diverse strains within the genus Burkholderia and such strains are not phylogenetically distinct from strains isolated from localities outside its distribution range. These findings lead to the hypothesis that I. superba does not exhibit rhizobia specificity at the intrageneric level. Testing of this hypothesis through analysis of its nodulation capability on soils from outside its distribution range is recommended. The fourth chapter of the thesis determined the extent of horizontal gene transfer among rhizobial genera in the Core Cape Subregion (CCR) of South Africa and reconstructed the ancestral symbionts of the legumes. Phylogenies of two chromosomal genes (16S rRNA and recA) and one nodulation gene (nodA) of rhizobia, isolated from diverse legumes in the CCR, were reconstructed using Bayesian and Maximum Likelihood techniques. A cophylogenetic analysis was used to test for congruence between the chromosomal and the nodA phylogenies. Five genera of rhizobia (Bradyrhizobium, Burkholderia, Ensifer, Mesorhizobium and Rhizobium) were studied. A phylogeny of the legumes was reconstructed from matK and rbcL DNA sequences and it was used to reconstruct their ancestral rhizobia, using Bayesian methods. The chromosomal phylogeny of the rhizobia was mostly incongruent with that of nodA, indicating potential horizontal inheritance of the latter. The nodA genes of Burkholderia, Mesorhizobium and Rhizobium had different evolutionary histories from their counterparts in other parts of the globe. Burkholderia was reconstructed as the ancestral symbionts of the CCR legumes. Evidence of co-diversification between the legumes and their symbionts was observed and this highlights a potential role of the legume-rhizobia interaction to the high diversity of legumes in the CCR. Finally, the availability of compatible rhizobia and their competitive ability are discussed as possible drivers for the lack of shared legumes between the CCR’s Fynbos biome and the Kwongan of Australia. Overall, the study shows that edaphic factors and biotic interactions (rhizobia) have significant influence on the distribution of legumes in the Cape Peninsula and the larger Core Cape Subregion of southern Africa. These findings are consistent with the theory that edaphic factors and biotic interactions have a strong influence on species distributions at local and site spatial scales.

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