Thesis (Ph. D.)--University of Wisconsin--Madison, 1942. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 23-24).

No description available.

Begonia is one of the ten largest plant genera and is found throughout the tropics. I have used Begonia section Gireoudia to study the genetics underlying vegetative diversity in tropical herbaceous plants. Section Gireoudia is a large Central American group. The section is remarkably diverse in morphology and habitat preference. It ranges from wet rainforests to seasonally dry forests. I have investigated variation in morphological, anatomical and ecophysiological differences for 21 species in Begonia section Gireoudia. Based on the observed variation, species in Begonia section Gireoudia form a complex and unique group that stands out from currently analysed taxa in the global scale of variation on the basis of leaf function and resource use strategy traits as well as their peculiar leaf anatomy. Traits directly related to leaf function such as photosynthesis and stomatal conductance has very low values which overlap with those of CAM and aquatic plants. Values for traits indicative of resource use such as leaf mass area (LMA) and leaf dry matter content (LDMC) are also very low in Begonia when compared with the values observed globally. The trait- trait correlations across the species in section Gireoudia were also investigated and revealed patterns in micromorphology and ecophysiology. Some of the traits measured are correlated with each other in apparently straightforward, well charaterised biological relationships e.g., the variation among Begonia species in stomatal conductance and net assimilation rate are positively correlated. On the other hand, the linkage of high Amass with high Nmass which is in large part the result of a direct causal relationship, has been observed at the global scale but this relationship is not significant in Begonia section Gireoudia. I examined B. plebeja and B. conchifolia, two very closely related though ecologically divergent species from Meso-America, in more detail. I detected significant differences between the species for a number of phenotypic variables which may be related to their habitat preferences. This suggested that environmental conditions have driven divergent evolution of phenotypic traits for these two species. Using a mapping population generated from hybrids between these two species I was able to examine the genetic basis of these differences. This revealed that although some traits (such as anthocyanin accumulation) appear to be under simple genetic control, most of the variation between species has complex genetic inheritance patterns. I used QTL analysis to identify significant QTLs for 20 physiological, anatomical and morphological traits which varied between these two species. Leaf shape traits appear to be largely influenced by a few loci of large effect, making these good potential targets for further analysis. The study also identified clusters of coincident QTLs for different correlated traits identifying pleiotropic genes or suites of linked loci.

Thesis--University of Michigan, 1931. / Cover title. "Papers from the Department of Botany, University of Michigan, no. 359." "Reprinted from the American journal of botany, vol. XIX, no. 4 ... April, 1932." "Literature cited": p. 381-383.

Thesis--University of Michigan, 1931. / Cover title. "Papers from the Department of Botany, University of Michigan, no. 359." "Reprinted from the American journal of botany, vol. XIX, no. 4 ... April, 1932." "Literature cited": p. 381-383.

Inaug.-Diss.--Utrecht. / Bibliography: p. [68]-74.

Begonia is one of the most diverse genera on the planet, with a species count approaching 2000 and a distribution across tropics in South America, Africa and South East Asia. The genus has occupied a vast range of niches; many highly variable growth forms can be found across the distribution, and species exhibit very diverse morphologies, even in closely related species. A recent study has revealed a putative whole genome duplication (WGD) event in the evolutionary history of Begonia, which has prompted an interest in investigating the impact gene and genome duplication has had on the diversification of Begonia. To answer questions about phenotypic and ecological diversification in Begonia, two species from South America, B. conchifolia and B. plebeja were chosen as study species based on their close phylogenetic relationship and divergent ecology and phenotype. RNA-seq data for six tissues from B. conchifolia and B. plebeja was generated using the Illumina sequencing platform, and normalised relative expression data was obtained by mapping reads to transcripts predicted from the B. conchifolia draft genome. A bioinformatics pipeline was devised to compare expression profiles across 6 different tissues between duplicated gene pairs shared between B. conchifolia and B. plebeja. Gene duplicate pairs were selected as candidates if they showed divergent expression in one species but not in another. Such duplicate pairs are suggestive of neofunctionalization in one species, providing evidence of a potential basis for phenotypic divergence and diversification between B. conchifolia and B. plebeja. Two duplicate pairs were identified as showing such divergent expression patterns as well as being functionally ecologically relevant, Chalcone Synthase and 3-Ketoacyl-CoA synthase, involved in anthocyanin biosynthesis and wax biosynthesis respectively. Investigation of expression and duplication patterns in both gene families showed the candidate gene families to be strikingly different. While 3-Ketoacyl-CoA synthase showed deeper duplications shared with outgroup taxa, Chalcone Synthase appeared to be expanded very recently, with a burst of duplications specific to the genus. 3-Ketoacyl-CoA synthase showed examples of partitioned expression by tissue for different gene family members, with at least five members of the gene family being highly expressed in one or two tissues only. Chalcone Synthase, however, showed dominance of one basal gene family member. Other Chalcone Synthase members, though expressed at lower levels, showed some evidence of reciprocal silencing in B. plebeja, though this pattern was not observed in B. conchifolia. Further investigation of the Chalcone Synthase gene family revealed lineage specific duplication in B. plebeja, and more extensive differential duplication patterns were found across other South American Begonias. Additionally, signals of positive selection were found in two branches on the Chalcone Synthase phylogeny.

O presente trabalho refere-se ao levantamento das espécies do gênero Begonia L. (Begoniaceae) de Minas Gerais. A família inclui dois gêneros: Hillebrandia Oliv., monotípico, endêmico do Arquipélago do Havaí e Begonia L. com cerca de 1400 espécies de ervas e subarbustos, largamente distribuídas pelos trópicos e subtrópicos. A maioria das espécies de Begonia apresenta potencial ornamental com folhas vistosas, frequentemente variegadas e diversas espécies são cultivadas no Brasil com essa finalidade. As espécies nativas do Brasil (aproximadamente 240) concentram-se na Mata Atlântica, sendo raras as espécies Amazônicas. De acordo com o levantamento, são encontradas 31 espécies de Begoniaceae em Minas Gerais, crescendo preferencialmente em formações cujo índice higrométrico é bastante elevado, à margem de cursos dágua, nas grotas úmidas, sobre ou entre rochas. O estudo baseou-se no levantamento bibliográfico, consulta a herbários e observações de campo. Constam também descrições, ilustrações, mapas de distribuição geográfica e comentários. / The present work refers to the taxonomic survey of the genus Begonia L. (Begoniaceae) in Minas Gerais State. This family is comprised of two genera: Hillebrandia Oliv., with one species that is endemic to the Hawaiian Islands and the only member of the family native to those islands, and Begonia L. with approximately 1,400 species of herbs and subshrubs that are widely distributed in tropics and subtropics. Most species of the genus Begonia have ornamental potential with showy leaves, frequently variegated and many species are cultivated in Brazil for this purpose. The native Brazilian species (240 - estimated figure) is concentrated on the Atlantic Forest, being Amazonian species rare. According to the survey, there are 31 species of the Begoniaceae in Minas Gerais State, growing up preferably near water, on the moist places, above or among rocks. The study was based on bibliographic review, consults to herbaria, collections and fields observation. Descriptions, illustrations, geographical distribution maps and comments are also presented about each species.

O presente trabalho refere-se ao levantamento das espécies do gênero Begonia L. (Begoniaceae) de Minas Gerais. A família inclui dois gêneros: Hillebrandia Oliv., monotípico, endêmico do Arquipélago do Havaí e Begonia L. com cerca de 1400 espécies de ervas e subarbustos, largamente distribuídas pelos trópicos e subtrópicos. A maioria das espécies de Begonia apresenta potencial ornamental com folhas vistosas, frequentemente variegadas e diversas espécies são cultivadas no Brasil com essa finalidade. As espécies nativas do Brasil (aproximadamente 240) concentram-se na Mata Atlântica, sendo raras as espécies Amazônicas. De acordo com o levantamento, são encontradas 31 espécies de Begoniaceae em Minas Gerais, crescendo preferencialmente em formações cujo índice higrométrico é bastante elevado, à margem de cursos dágua, nas grotas úmidas, sobre ou entre rochas. O estudo baseou-se no levantamento bibliográfico, consulta a herbários e observações de campo. Constam também descrições, ilustrações, mapas de distribuição geográfica e comentários. / The present work refers to the taxonomic survey of the genus Begonia L. (Begoniaceae) in Minas Gerais State. This family is comprised of two genera: Hillebrandia Oliv., with one species that is endemic to the Hawaiian Islands and the only member of the family native to those islands, and Begonia L. with approximately 1,400 species of herbs and subshrubs that are widely distributed in tropics and subtropics. Most species of the genus Begonia have ornamental potential with showy leaves, frequently variegated and many species are cultivated in Brazil for this purpose. The native Brazilian species (240 - estimated figure) is concentrated on the Atlantic Forest, being Amazonian species rare. According to the survey, there are 31 species of the Begoniaceae in Minas Gerais State, growing up preferably near water, on the moist places, above or among rocks. The study was based on bibliographic review, consults to herbaria, collections and fields observation. Descriptions, illustrations, geographical distribution maps and comments are also presented about each species.

Begonia L. is one of the largest plant genera, comprising over 1500 species. Weak species cohesion, and the rapid evolution of reproductive barriers in allopatry, are two processes that have been postulated to explain the generation of such hyper-diversity of taxa within a single genus of plants. The aim of this thesis is to investigate whether these factors are likely to have been important contributors to the diversity of species found in Central American Begonia. Species cohesion was analysed in the widespread Central American species Begonia heracleifolia and B. nelumbiifolia. Interpopulation seed flow was estimated with seven plastid microsatellites. Breeding system estimates and measures of genetic differentiation at nine nuclear microsatellites were used to infer levels of interpopulation pollen flow. Controlled crosses were employed to assess the strength of reproductive barriers both between populations within species, and between species differing in ecology. The potential for gene flow between species in the wild was assessed in natural hybrid zones using molecular markers. Finally a quantitative trait locus (QTL) approach was employed to investigate the genetic basis of reproductive traits that differ between species. No plastid polymorphisms were found in B. nelumbiifolia, suggesting it has been through a recent population bottleneck. In contrast, B. heracleifolia possessed many plastid haplotypes that were strongly differentiated between populations (G’ST = 0.829). Nuclear microsatellites showed high genetic differentiation within species, and both species were self-compatible and self-fertilize at a moderate rate (B. heracleifolia F’ST = 0.506, FIS = 0.249; B. nelumbiifolia F’ST = 0.439, FIS = 0.380). F1s between ecologically similar B. heracleifolia and B. sericoneura were partly fertile (2-5% seed set), and F1s and early generation backcrosses were found in a hybrid swarm. F1s between B. heracleifolia and the ecologically contrasting B. nelumbiifolia were pollen sterile, and 3 hybrid swarms showed no evidence of hybrids beyond the F1 generation. Seven QTL were found for reproductive traits, including: sex ratio, pollen sterility and stamen number. The population biology of Begonia, with limited seed and pollen dispersal, small population sizes and frequent self-fertilization predisposes them to genetic isolation, increasing the chances that reproductive barriers evolve. These characteristics may underlie the large number of endemics in Begonia.