Evolution of floral organisation and architecture in Boraginales and Geraniales
Evolution of floral organisation and architecture in Boraginales and Geraniales
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DissertationDate of Exam
03.02.2020Date of Publication
13.08.2020Advisor
Weigend, MaximilianCo-Referee
Smets, Erik F.Metadata
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Abstract
In this thesis, development, morphology and anatomy of structures from selected taxa from the Gera- niales and Boraginales are studied. Furthermore, the integration of structures such as stamen-corolla tube modifications and nectaries into floral architecture is investigated. The results of the investiga- tions are interpreted in the context of the current phylogenetic understanding of the study groups.
The following questions are addressed in this thesis:
1. Are the gynoecium and fruit of Heliotropium sect. Heliothamnus structurally correspondent to those of the Boraginaceae?
2. How does the flower of Codon develop?
3. How do the stamen-corolla tube modifications of Boraginaceae develop, how are they integrated into floral architecture and is there a phylogenetic pattern?
4. How do the stamen-corolla tube modifications of Hydrophyllaceae develop, how are they inte- grated into floral architecture and is there a phylogenetic pattern underlying these structures?
5. How are the internal floral spaces, enclosed by stamen-corolla tube modifications, in Hydrophyl- laceae configured and how are the modifications contributing to the floral architecture?
6. What is the relationship between floral nectaries and floral architecture in Geraniaceae and Hypseocharitaceae?
7. What is the internal floral space and how does it contribute to our understanding of floral ecology and evolution?
8. Can the various stamen-corolla tube modifications found in different Boraginales families be homologise and if so, is it possible to propose an evolutionary series?
To address these questions, the following approaches and methods were used: floral morphology, anatomy and development based on scanning electron microscopy, serial sectioning and light mi- croscopy, and high-resolution x-ray computed tomography (HRXCT) respective micro-computed to- mography (µCT). Based on 3D-HRXCT- and µCT-scans, segmentation of the floral surfaces and internal spaces was conducted. Furthermore, 3D-landmarking based 3D-geometric morphometric analyses were employed. The phylogenetic signal in the 3D-landmarks was tested for on the basis of phylogenetic reconstruction.
This is a cumulative thesis. Chapters 2, 3, 5 and 7 are published and chapter 4 is submitted. Chapters 6 and 8 follow the structure of scientific articles and are in preparation for submission.
Chapter 1 is the general introduction. It introduces the two main research topics: i) study of floral structure in the context of phylogeny and ii) floral architecture. Furthermore, hypotheses, research questions and objectives are formulated and an overview of the thesis is given.
In chapter 2, gynoecium and fruit development in Heliotropium sect. Heliothamnus is investigated using an ontogenetic approach based on scanning electron microscopy, light microscopy and HRXCT. The columella, a structure between the nutlets on which the style is inserted, similar to that found in all Boraginaceae species, was proposed for this section, based on light microscopic observations. We found that a columella is absent and instead a disrupting tissue within the ovary can be ob- served. Based on phylogenetic evidence, homology of columella and disrupting tissue was rejected a priori, the morphological and developmental evidence presented here, further indicates that structural correspondence can be rejected as well. In chapter 3, flower and fruit development of Codon from monogeneric Codonaceae is studied using scanning electron microscopy and light microscopy. Codonaceae are sister to Wellstediaceae and Boraginaceae on the Boraginales I clade. They have polymerous flowers with a 10- to 20-merous calyx, corolla and androecium. The bicarpellate gynoecium has a lobed nectary disc at the base and develops into a capsule. Between filament bases and corolla tube apically broadened septa are formed in late floral developmental stages. The septa compartmentalise the flower which results in revolver architecture.
Chapter 4 is the first systematic study of faucal and basal scales of Boraginaceae. Based on a systematic sampling, their development and morphology are investigated using scanning electron microscopy. Furthermore, the scales integration into floral architecture is visualised using µCT-data and the results are mapped onto a recent phylogeny of the family. Faucal scales were present in 18 and basal scales in 27 out of 29 species. Their development in late floral ontogeny indicates that they are peramorphoses. Faucal scales might have a function in pollination and other ecological interactions, as they tend to narrow the entrance to the corolla tube, are in close proximity to the anthers and, in some species, are involved in anther cone formation. The role of basal scales remains unknown. However, they are fairly conserved in their position within the flower and usually cover either the nectary disc or the entire ovary. Both types of scales can be found in all clades of Boraginaceae. No phylogenetic patterns in presence or absence of faucal and basal scales or in their combinations with other floral architectural characters are found. Only anther cone formation is commonly either associated with faucal scales, or the anthers themselves are modified. Basal scales are probably homologous to stamen-corolla tube modifications found in other Boraginales families. Faucal scales, on the other hand, appear to be an apomorphy of Boraginaceae.
In chapter 5, the development and morphology of stamen-corolla tube modifications and nectaries of Hydrophyllaceae are described using scanning electron microscopy. All Hydrophyllaceae species have ten modifications in antepetalous position. Each filament is basally connected to two adjacent modifications. The development of the modifications starts in late stages of floral development and is correlated to the differential elongation of the three parts of the stamen-corolla tube. The nectary is a gynoecial nectary disc at the base of the ovary. The disc is lobed and in the majority of species, nec- tarostomata are restricted to the tips of the lobes in antepetalous position. Always two modifications are synorganised with the nectary glands and form different types of pockets or tubes, which compart- mentalise the flower resulting in revolver architecture. The position of the modifications in relation to the basal part of the corolla tube indicates variability in revolver architecture. An evolutionary series of the stamen-corolla tube modifications is proposed.
Chapter 6 explores floral architecture and the integration of stamen-corolla tube modifications into floral architecture in Hydrophyllaceae. The study is based on HRXCT- and µCT-scans and molecular phylogenetics. The scans are used for a 3D-landmarking based 3D-geometric morphometric approach. Furthermore, the spaces enclosed by the modifications are visualised through segmentation in the 3D-models. Three types of spatial configurations are described: completely, incompletely and non- compartmentalised flowers. The 3D-geometric morphometric analysis reveals that modification length and position as well as the corolla tube shape have the greatest effect on floral architecture. Both the compartment configuration and the 3D-geometric morphometric analysis show a clear phylogenetic pattern and a test indicates phylogenetic signal. To test the influence of the different compartment configurations on floral function, a nectar removal experiment was conducted by probing each of the five compartments of the flower separately. In the completely compartmentalised flowers, each compartment holds a similar amount of nectar. In incompletely compartmentalised flowers, the results are more variable. In some species, the first probe removed the majority of nectar. In other species, the results are similar to the completely compartmentalised flowers. In non-compartmentalised flowers, the results were similarly variable. The results indicate that not just the configuration of the stamen- corolla tube modifications and the spaces they enclose, but also nectar amount and viscosity have an effect on floral architecture and function.
In chapter 7, the relationship between nectaries and floral architecture in Hypseocharitaceae and Geraniaceae is explored using an ontogenetic approach based on scanning electron microscopy and light microscopy. The receptacular nectaries are in antesepalous position and are initiated in late stages of flower development. Nectar is secreted through nectarostomata. The development of the nectary glands is correlated with the receptacle development, which elongates in most species and forms a short anthophore. In Pelargonium a secondary meristem forms at the level of the single nectary gland lifting up the entire flower, except for the nectary gland. As a result, a receptacular cavity is formed around the gland. The nectary is integrated into floral architecture. Besides the anthophore and the receptacular cavity, the formation of stamen triplets is one of the key features of floral architecture in both families. In some Geranium species, the petal bases are modified, resulting in an elaborate revolver architecture. In the other species, stamen triplets, petal bases and sepals result in a lax revolver architecture. The functionality of these revolver architectures might depend on nectar properties. An evolutionary series of floral architecture in Hypseocharitaceae and Geraniaceae is proposed.
Chapter 8 introduces the concept of the internal floral space. The internal floral space is the air-filled volume of a flower. It can be visualised using 3D-visualisation methods, segmentation and surface rendering. The internal floral space can be equally or unequally compartmentalised. An application of this concept is demonstrated for two Nasa species (Loasaceae), Geranium robertianum (Geraniaceae) and Hydrophyllaceae based on the results of chapter 6. The internal floral space harbours great potential for ecological and evolutionary studies. It can be used for i) comparative morphological approaches, ii) to visualise complex spatial relations, and iii) in volumetric studies.
Chapter 9 are the general conclusions of this thesis. Here, the results of the individual chapters are discussed in the light of the main topics of this thesis and are put into a larger context. Furthermore, an evolutionary series for the stamen-corolla tube modifications of the Boraginales is proposed, taking into account the results of chapters 3, 4 and 5 as well as the information available from the literature. Finally, future research questions, which are related to this thesis, are discussed.
The following questions are addressed in this thesis:
1. Are the gynoecium and fruit of Heliotropium sect. Heliothamnus structurally correspondent to those of the Boraginaceae?
2. How does the flower of Codon develop?
3. How do the stamen-corolla tube modifications of Boraginaceae develop, how are they integrated into floral architecture and is there a phylogenetic pattern?
4. How do the stamen-corolla tube modifications of Hydrophyllaceae develop, how are they inte- grated into floral architecture and is there a phylogenetic pattern underlying these structures?
5. How are the internal floral spaces, enclosed by stamen-corolla tube modifications, in Hydrophyl- laceae configured and how are the modifications contributing to the floral architecture?
6. What is the relationship between floral nectaries and floral architecture in Geraniaceae and Hypseocharitaceae?
7. What is the internal floral space and how does it contribute to our understanding of floral ecology and evolution?
8. Can the various stamen-corolla tube modifications found in different Boraginales families be homologise and if so, is it possible to propose an evolutionary series?
To address these questions, the following approaches and methods were used: floral morphology, anatomy and development based on scanning electron microscopy, serial sectioning and light mi- croscopy, and high-resolution x-ray computed tomography (HRXCT) respective micro-computed to- mography (µCT). Based on 3D-HRXCT- and µCT-scans, segmentation of the floral surfaces and internal spaces was conducted. Furthermore, 3D-landmarking based 3D-geometric morphometric analyses were employed. The phylogenetic signal in the 3D-landmarks was tested for on the basis of phylogenetic reconstruction.
This is a cumulative thesis. Chapters 2, 3, 5 and 7 are published and chapter 4 is submitted. Chapters 6 and 8 follow the structure of scientific articles and are in preparation for submission.
Chapter 1 is the general introduction. It introduces the two main research topics: i) study of floral structure in the context of phylogeny and ii) floral architecture. Furthermore, hypotheses, research questions and objectives are formulated and an overview of the thesis is given.
In chapter 2, gynoecium and fruit development in Heliotropium sect. Heliothamnus is investigated using an ontogenetic approach based on scanning electron microscopy, light microscopy and HRXCT. The columella, a structure between the nutlets on which the style is inserted, similar to that found in all Boraginaceae species, was proposed for this section, based on light microscopic observations. We found that a columella is absent and instead a disrupting tissue within the ovary can be ob- served. Based on phylogenetic evidence, homology of columella and disrupting tissue was rejected a priori, the morphological and developmental evidence presented here, further indicates that structural correspondence can be rejected as well. In chapter 3, flower and fruit development of Codon from monogeneric Codonaceae is studied using scanning electron microscopy and light microscopy. Codonaceae are sister to Wellstediaceae and Boraginaceae on the Boraginales I clade. They have polymerous flowers with a 10- to 20-merous calyx, corolla and androecium. The bicarpellate gynoecium has a lobed nectary disc at the base and develops into a capsule. Between filament bases and corolla tube apically broadened septa are formed in late floral developmental stages. The septa compartmentalise the flower which results in revolver architecture.
Chapter 4 is the first systematic study of faucal and basal scales of Boraginaceae. Based on a systematic sampling, their development and morphology are investigated using scanning electron microscopy. Furthermore, the scales integration into floral architecture is visualised using µCT-data and the results are mapped onto a recent phylogeny of the family. Faucal scales were present in 18 and basal scales in 27 out of 29 species. Their development in late floral ontogeny indicates that they are peramorphoses. Faucal scales might have a function in pollination and other ecological interactions, as they tend to narrow the entrance to the corolla tube, are in close proximity to the anthers and, in some species, are involved in anther cone formation. The role of basal scales remains unknown. However, they are fairly conserved in their position within the flower and usually cover either the nectary disc or the entire ovary. Both types of scales can be found in all clades of Boraginaceae. No phylogenetic patterns in presence or absence of faucal and basal scales or in their combinations with other floral architectural characters are found. Only anther cone formation is commonly either associated with faucal scales, or the anthers themselves are modified. Basal scales are probably homologous to stamen-corolla tube modifications found in other Boraginales families. Faucal scales, on the other hand, appear to be an apomorphy of Boraginaceae.
In chapter 5, the development and morphology of stamen-corolla tube modifications and nectaries of Hydrophyllaceae are described using scanning electron microscopy. All Hydrophyllaceae species have ten modifications in antepetalous position. Each filament is basally connected to two adjacent modifications. The development of the modifications starts in late stages of floral development and is correlated to the differential elongation of the three parts of the stamen-corolla tube. The nectary is a gynoecial nectary disc at the base of the ovary. The disc is lobed and in the majority of species, nec- tarostomata are restricted to the tips of the lobes in antepetalous position. Always two modifications are synorganised with the nectary glands and form different types of pockets or tubes, which compart- mentalise the flower resulting in revolver architecture. The position of the modifications in relation to the basal part of the corolla tube indicates variability in revolver architecture. An evolutionary series of the stamen-corolla tube modifications is proposed.
Chapter 6 explores floral architecture and the integration of stamen-corolla tube modifications into floral architecture in Hydrophyllaceae. The study is based on HRXCT- and µCT-scans and molecular phylogenetics. The scans are used for a 3D-landmarking based 3D-geometric morphometric approach. Furthermore, the spaces enclosed by the modifications are visualised through segmentation in the 3D-models. Three types of spatial configurations are described: completely, incompletely and non- compartmentalised flowers. The 3D-geometric morphometric analysis reveals that modification length and position as well as the corolla tube shape have the greatest effect on floral architecture. Both the compartment configuration and the 3D-geometric morphometric analysis show a clear phylogenetic pattern and a test indicates phylogenetic signal. To test the influence of the different compartment configurations on floral function, a nectar removal experiment was conducted by probing each of the five compartments of the flower separately. In the completely compartmentalised flowers, each compartment holds a similar amount of nectar. In incompletely compartmentalised flowers, the results are more variable. In some species, the first probe removed the majority of nectar. In other species, the results are similar to the completely compartmentalised flowers. In non-compartmentalised flowers, the results were similarly variable. The results indicate that not just the configuration of the stamen- corolla tube modifications and the spaces they enclose, but also nectar amount and viscosity have an effect on floral architecture and function.
In chapter 7, the relationship between nectaries and floral architecture in Hypseocharitaceae and Geraniaceae is explored using an ontogenetic approach based on scanning electron microscopy and light microscopy. The receptacular nectaries are in antesepalous position and are initiated in late stages of flower development. Nectar is secreted through nectarostomata. The development of the nectary glands is correlated with the receptacle development, which elongates in most species and forms a short anthophore. In Pelargonium a secondary meristem forms at the level of the single nectary gland lifting up the entire flower, except for the nectary gland. As a result, a receptacular cavity is formed around the gland. The nectary is integrated into floral architecture. Besides the anthophore and the receptacular cavity, the formation of stamen triplets is one of the key features of floral architecture in both families. In some Geranium species, the petal bases are modified, resulting in an elaborate revolver architecture. In the other species, stamen triplets, petal bases and sepals result in a lax revolver architecture. The functionality of these revolver architectures might depend on nectar properties. An evolutionary series of floral architecture in Hypseocharitaceae and Geraniaceae is proposed.
Chapter 8 introduces the concept of the internal floral space. The internal floral space is the air-filled volume of a flower. It can be visualised using 3D-visualisation methods, segmentation and surface rendering. The internal floral space can be equally or unequally compartmentalised. An application of this concept is demonstrated for two Nasa species (Loasaceae), Geranium robertianum (Geraniaceae) and Hydrophyllaceae based on the results of chapter 6. The internal floral space harbours great potential for ecological and evolutionary studies. It can be used for i) comparative morphological approaches, ii) to visualise complex spatial relations, and iii) in volumetric studies.
Chapter 9 are the general conclusions of this thesis. Here, the results of the individual chapters are discussed in the light of the main topics of this thesis and are put into a larger context. Furthermore, an evolutionary series for the stamen-corolla tube modifications of the Boraginales is proposed, taking into account the results of chapters 3, 4 and 5 as well as the information available from the literature. Finally, future research questions, which are related to this thesis, are discussed.
Subjects
Blütenmorphologie, Blütenarchitektur, 3D-Visualisierung, Blüten- und Fruchtevolution, Boraginales, Geraniales, Flower morphology, Floral architecture, 3D-visualisation, Flower and fruit evolution
Classification (DDC)
580 Pflanzen (Botanik)Jeiter, Julius: Evolution of floral organisation and architecture in Boraginales and Geraniales. - Bonn, 2020. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-59332
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-59332
@phdthesis{handle:20.500.11811/8523,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-59332,
author = {{Julius Jeiter}},
title = {Evolution of floral organisation and architecture in Boraginales and Geraniales},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2020,
month = aug,
note = {In this thesis, development, morphology and anatomy of structures from selected taxa from the Gera- niales and Boraginales are studied. Furthermore, the integration of structures such as stamen-corolla tube modifications and nectaries into floral architecture is investigated. The results of the investiga- tions are interpreted in the context of the current phylogenetic understanding of the study groups.
The following questions are addressed in this thesis:
1. Are the gynoecium and fruit of Heliotropium sect. Heliothamnus structurally correspondent to those of the Boraginaceae?
2. How does the flower of Codon develop?
3. How do the stamen-corolla tube modifications of Boraginaceae develop, how are they integrated into floral architecture and is there a phylogenetic pattern?
4. How do the stamen-corolla tube modifications of Hydrophyllaceae develop, how are they inte- grated into floral architecture and is there a phylogenetic pattern underlying these structures?
5. How are the internal floral spaces, enclosed by stamen-corolla tube modifications, in Hydrophyl- laceae configured and how are the modifications contributing to the floral architecture?
6. What is the relationship between floral nectaries and floral architecture in Geraniaceae and Hypseocharitaceae?
7. What is the internal floral space and how does it contribute to our understanding of floral ecology and evolution?
8. Can the various stamen-corolla tube modifications found in different Boraginales families be homologise and if so, is it possible to propose an evolutionary series?
To address these questions, the following approaches and methods were used: floral morphology, anatomy and development based on scanning electron microscopy, serial sectioning and light mi- croscopy, and high-resolution x-ray computed tomography (HRXCT) respective micro-computed to- mography (µCT). Based on 3D-HRXCT- and µCT-scans, segmentation of the floral surfaces and internal spaces was conducted. Furthermore, 3D-landmarking based 3D-geometric morphometric analyses were employed. The phylogenetic signal in the 3D-landmarks was tested for on the basis of phylogenetic reconstruction.
This is a cumulative thesis. Chapters 2, 3, 5 and 7 are published and chapter 4 is submitted. Chapters 6 and 8 follow the structure of scientific articles and are in preparation for submission.
Chapter 1 is the general introduction. It introduces the two main research topics: i) study of floral structure in the context of phylogeny and ii) floral architecture. Furthermore, hypotheses, research questions and objectives are formulated and an overview of the thesis is given.
In chapter 2, gynoecium and fruit development in Heliotropium sect. Heliothamnus is investigated using an ontogenetic approach based on scanning electron microscopy, light microscopy and HRXCT. The columella, a structure between the nutlets on which the style is inserted, similar to that found in all Boraginaceae species, was proposed for this section, based on light microscopic observations. We found that a columella is absent and instead a disrupting tissue within the ovary can be ob- served. Based on phylogenetic evidence, homology of columella and disrupting tissue was rejected a priori, the morphological and developmental evidence presented here, further indicates that structural correspondence can be rejected as well. In chapter 3, flower and fruit development of Codon from monogeneric Codonaceae is studied using scanning electron microscopy and light microscopy. Codonaceae are sister to Wellstediaceae and Boraginaceae on the Boraginales I clade. They have polymerous flowers with a 10- to 20-merous calyx, corolla and androecium. The bicarpellate gynoecium has a lobed nectary disc at the base and develops into a capsule. Between filament bases and corolla tube apically broadened septa are formed in late floral developmental stages. The septa compartmentalise the flower which results in revolver architecture.
Chapter 4 is the first systematic study of faucal and basal scales of Boraginaceae. Based on a systematic sampling, their development and morphology are investigated using scanning electron microscopy. Furthermore, the scales integration into floral architecture is visualised using µCT-data and the results are mapped onto a recent phylogeny of the family. Faucal scales were present in 18 and basal scales in 27 out of 29 species. Their development in late floral ontogeny indicates that they are peramorphoses. Faucal scales might have a function in pollination and other ecological interactions, as they tend to narrow the entrance to the corolla tube, are in close proximity to the anthers and, in some species, are involved in anther cone formation. The role of basal scales remains unknown. However, they are fairly conserved in their position within the flower and usually cover either the nectary disc or the entire ovary. Both types of scales can be found in all clades of Boraginaceae. No phylogenetic patterns in presence or absence of faucal and basal scales or in their combinations with other floral architectural characters are found. Only anther cone formation is commonly either associated with faucal scales, or the anthers themselves are modified. Basal scales are probably homologous to stamen-corolla tube modifications found in other Boraginales families. Faucal scales, on the other hand, appear to be an apomorphy of Boraginaceae.
In chapter 5, the development and morphology of stamen-corolla tube modifications and nectaries of Hydrophyllaceae are described using scanning electron microscopy. All Hydrophyllaceae species have ten modifications in antepetalous position. Each filament is basally connected to two adjacent modifications. The development of the modifications starts in late stages of floral development and is correlated to the differential elongation of the three parts of the stamen-corolla tube. The nectary is a gynoecial nectary disc at the base of the ovary. The disc is lobed and in the majority of species, nec- tarostomata are restricted to the tips of the lobes in antepetalous position. Always two modifications are synorganised with the nectary glands and form different types of pockets or tubes, which compart- mentalise the flower resulting in revolver architecture. The position of the modifications in relation to the basal part of the corolla tube indicates variability in revolver architecture. An evolutionary series of the stamen-corolla tube modifications is proposed.
Chapter 6 explores floral architecture and the integration of stamen-corolla tube modifications into floral architecture in Hydrophyllaceae. The study is based on HRXCT- and µCT-scans and molecular phylogenetics. The scans are used for a 3D-landmarking based 3D-geometric morphometric approach. Furthermore, the spaces enclosed by the modifications are visualised through segmentation in the 3D-models. Three types of spatial configurations are described: completely, incompletely and non- compartmentalised flowers. The 3D-geometric morphometric analysis reveals that modification length and position as well as the corolla tube shape have the greatest effect on floral architecture. Both the compartment configuration and the 3D-geometric morphometric analysis show a clear phylogenetic pattern and a test indicates phylogenetic signal. To test the influence of the different compartment configurations on floral function, a nectar removal experiment was conducted by probing each of the five compartments of the flower separately. In the completely compartmentalised flowers, each compartment holds a similar amount of nectar. In incompletely compartmentalised flowers, the results are more variable. In some species, the first probe removed the majority of nectar. In other species, the results are similar to the completely compartmentalised flowers. In non-compartmentalised flowers, the results were similarly variable. The results indicate that not just the configuration of the stamen- corolla tube modifications and the spaces they enclose, but also nectar amount and viscosity have an effect on floral architecture and function.
In chapter 7, the relationship between nectaries and floral architecture in Hypseocharitaceae and Geraniaceae is explored using an ontogenetic approach based on scanning electron microscopy and light microscopy. The receptacular nectaries are in antesepalous position and are initiated in late stages of flower development. Nectar is secreted through nectarostomata. The development of the nectary glands is correlated with the receptacle development, which elongates in most species and forms a short anthophore. In Pelargonium a secondary meristem forms at the level of the single nectary gland lifting up the entire flower, except for the nectary gland. As a result, a receptacular cavity is formed around the gland. The nectary is integrated into floral architecture. Besides the anthophore and the receptacular cavity, the formation of stamen triplets is one of the key features of floral architecture in both families. In some Geranium species, the petal bases are modified, resulting in an elaborate revolver architecture. In the other species, stamen triplets, petal bases and sepals result in a lax revolver architecture. The functionality of these revolver architectures might depend on nectar properties. An evolutionary series of floral architecture in Hypseocharitaceae and Geraniaceae is proposed.
Chapter 8 introduces the concept of the internal floral space. The internal floral space is the air-filled volume of a flower. It can be visualised using 3D-visualisation methods, segmentation and surface rendering. The internal floral space can be equally or unequally compartmentalised. An application of this concept is demonstrated for two Nasa species (Loasaceae), Geranium robertianum (Geraniaceae) and Hydrophyllaceae based on the results of chapter 6. The internal floral space harbours great potential for ecological and evolutionary studies. It can be used for i) comparative morphological approaches, ii) to visualise complex spatial relations, and iii) in volumetric studies.
Chapter 9 are the general conclusions of this thesis. Here, the results of the individual chapters are discussed in the light of the main topics of this thesis and are put into a larger context. Furthermore, an evolutionary series for the stamen-corolla tube modifications of the Boraginales is proposed, taking into account the results of chapters 3, 4 and 5 as well as the information available from the literature. Finally, future research questions, which are related to this thesis, are discussed.},
url = {https://hdl.handle.net/20.500.11811/8523}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-59332,
author = {{Julius Jeiter}},
title = {Evolution of floral organisation and architecture in Boraginales and Geraniales},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2020,
month = aug,
note = {In this thesis, development, morphology and anatomy of structures from selected taxa from the Gera- niales and Boraginales are studied. Furthermore, the integration of structures such as stamen-corolla tube modifications and nectaries into floral architecture is investigated. The results of the investiga- tions are interpreted in the context of the current phylogenetic understanding of the study groups.
The following questions are addressed in this thesis:
1. Are the gynoecium and fruit of Heliotropium sect. Heliothamnus structurally correspondent to those of the Boraginaceae?
2. How does the flower of Codon develop?
3. How do the stamen-corolla tube modifications of Boraginaceae develop, how are they integrated into floral architecture and is there a phylogenetic pattern?
4. How do the stamen-corolla tube modifications of Hydrophyllaceae develop, how are they inte- grated into floral architecture and is there a phylogenetic pattern underlying these structures?
5. How are the internal floral spaces, enclosed by stamen-corolla tube modifications, in Hydrophyl- laceae configured and how are the modifications contributing to the floral architecture?
6. What is the relationship between floral nectaries and floral architecture in Geraniaceae and Hypseocharitaceae?
7. What is the internal floral space and how does it contribute to our understanding of floral ecology and evolution?
8. Can the various stamen-corolla tube modifications found in different Boraginales families be homologise and if so, is it possible to propose an evolutionary series?
To address these questions, the following approaches and methods were used: floral morphology, anatomy and development based on scanning electron microscopy, serial sectioning and light mi- croscopy, and high-resolution x-ray computed tomography (HRXCT) respective micro-computed to- mography (µCT). Based on 3D-HRXCT- and µCT-scans, segmentation of the floral surfaces and internal spaces was conducted. Furthermore, 3D-landmarking based 3D-geometric morphometric analyses were employed. The phylogenetic signal in the 3D-landmarks was tested for on the basis of phylogenetic reconstruction.
This is a cumulative thesis. Chapters 2, 3, 5 and 7 are published and chapter 4 is submitted. Chapters 6 and 8 follow the structure of scientific articles and are in preparation for submission.
Chapter 1 is the general introduction. It introduces the two main research topics: i) study of floral structure in the context of phylogeny and ii) floral architecture. Furthermore, hypotheses, research questions and objectives are formulated and an overview of the thesis is given.
In chapter 2, gynoecium and fruit development in Heliotropium sect. Heliothamnus is investigated using an ontogenetic approach based on scanning electron microscopy, light microscopy and HRXCT. The columella, a structure between the nutlets on which the style is inserted, similar to that found in all Boraginaceae species, was proposed for this section, based on light microscopic observations. We found that a columella is absent and instead a disrupting tissue within the ovary can be ob- served. Based on phylogenetic evidence, homology of columella and disrupting tissue was rejected a priori, the morphological and developmental evidence presented here, further indicates that structural correspondence can be rejected as well. In chapter 3, flower and fruit development of Codon from monogeneric Codonaceae is studied using scanning electron microscopy and light microscopy. Codonaceae are sister to Wellstediaceae and Boraginaceae on the Boraginales I clade. They have polymerous flowers with a 10- to 20-merous calyx, corolla and androecium. The bicarpellate gynoecium has a lobed nectary disc at the base and develops into a capsule. Between filament bases and corolla tube apically broadened septa are formed in late floral developmental stages. The septa compartmentalise the flower which results in revolver architecture.
Chapter 4 is the first systematic study of faucal and basal scales of Boraginaceae. Based on a systematic sampling, their development and morphology are investigated using scanning electron microscopy. Furthermore, the scales integration into floral architecture is visualised using µCT-data and the results are mapped onto a recent phylogeny of the family. Faucal scales were present in 18 and basal scales in 27 out of 29 species. Their development in late floral ontogeny indicates that they are peramorphoses. Faucal scales might have a function in pollination and other ecological interactions, as they tend to narrow the entrance to the corolla tube, are in close proximity to the anthers and, in some species, are involved in anther cone formation. The role of basal scales remains unknown. However, they are fairly conserved in their position within the flower and usually cover either the nectary disc or the entire ovary. Both types of scales can be found in all clades of Boraginaceae. No phylogenetic patterns in presence or absence of faucal and basal scales or in their combinations with other floral architectural characters are found. Only anther cone formation is commonly either associated with faucal scales, or the anthers themselves are modified. Basal scales are probably homologous to stamen-corolla tube modifications found in other Boraginales families. Faucal scales, on the other hand, appear to be an apomorphy of Boraginaceae.
In chapter 5, the development and morphology of stamen-corolla tube modifications and nectaries of Hydrophyllaceae are described using scanning electron microscopy. All Hydrophyllaceae species have ten modifications in antepetalous position. Each filament is basally connected to two adjacent modifications. The development of the modifications starts in late stages of floral development and is correlated to the differential elongation of the three parts of the stamen-corolla tube. The nectary is a gynoecial nectary disc at the base of the ovary. The disc is lobed and in the majority of species, nec- tarostomata are restricted to the tips of the lobes in antepetalous position. Always two modifications are synorganised with the nectary glands and form different types of pockets or tubes, which compart- mentalise the flower resulting in revolver architecture. The position of the modifications in relation to the basal part of the corolla tube indicates variability in revolver architecture. An evolutionary series of the stamen-corolla tube modifications is proposed.
Chapter 6 explores floral architecture and the integration of stamen-corolla tube modifications into floral architecture in Hydrophyllaceae. The study is based on HRXCT- and µCT-scans and molecular phylogenetics. The scans are used for a 3D-landmarking based 3D-geometric morphometric approach. Furthermore, the spaces enclosed by the modifications are visualised through segmentation in the 3D-models. Three types of spatial configurations are described: completely, incompletely and non- compartmentalised flowers. The 3D-geometric morphometric analysis reveals that modification length and position as well as the corolla tube shape have the greatest effect on floral architecture. Both the compartment configuration and the 3D-geometric morphometric analysis show a clear phylogenetic pattern and a test indicates phylogenetic signal. To test the influence of the different compartment configurations on floral function, a nectar removal experiment was conducted by probing each of the five compartments of the flower separately. In the completely compartmentalised flowers, each compartment holds a similar amount of nectar. In incompletely compartmentalised flowers, the results are more variable. In some species, the first probe removed the majority of nectar. In other species, the results are similar to the completely compartmentalised flowers. In non-compartmentalised flowers, the results were similarly variable. The results indicate that not just the configuration of the stamen- corolla tube modifications and the spaces they enclose, but also nectar amount and viscosity have an effect on floral architecture and function.
In chapter 7, the relationship between nectaries and floral architecture in Hypseocharitaceae and Geraniaceae is explored using an ontogenetic approach based on scanning electron microscopy and light microscopy. The receptacular nectaries are in antesepalous position and are initiated in late stages of flower development. Nectar is secreted through nectarostomata. The development of the nectary glands is correlated with the receptacle development, which elongates in most species and forms a short anthophore. In Pelargonium a secondary meristem forms at the level of the single nectary gland lifting up the entire flower, except for the nectary gland. As a result, a receptacular cavity is formed around the gland. The nectary is integrated into floral architecture. Besides the anthophore and the receptacular cavity, the formation of stamen triplets is one of the key features of floral architecture in both families. In some Geranium species, the petal bases are modified, resulting in an elaborate revolver architecture. In the other species, stamen triplets, petal bases and sepals result in a lax revolver architecture. The functionality of these revolver architectures might depend on nectar properties. An evolutionary series of floral architecture in Hypseocharitaceae and Geraniaceae is proposed.
Chapter 8 introduces the concept of the internal floral space. The internal floral space is the air-filled volume of a flower. It can be visualised using 3D-visualisation methods, segmentation and surface rendering. The internal floral space can be equally or unequally compartmentalised. An application of this concept is demonstrated for two Nasa species (Loasaceae), Geranium robertianum (Geraniaceae) and Hydrophyllaceae based on the results of chapter 6. The internal floral space harbours great potential for ecological and evolutionary studies. It can be used for i) comparative morphological approaches, ii) to visualise complex spatial relations, and iii) in volumetric studies.
Chapter 9 are the general conclusions of this thesis. Here, the results of the individual chapters are discussed in the light of the main topics of this thesis and are put into a larger context. Furthermore, an evolutionary series for the stamen-corolla tube modifications of the Boraginales is proposed, taking into account the results of chapters 3, 4 and 5 as well as the information available from the literature. Finally, future research questions, which are related to this thesis, are discussed.},
url = {https://hdl.handle.net/20.500.11811/8523}
}
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