Revision of the Genus Asterella P. Beauv. in Eurasia

About this book

Language: English

This study is based on a study at Trinity College, Dublin, for a doctoral degree. It constitutes a taxonomic revision of the genus Asterella in Eurasia. Asterella belongs to the family Aytoniaceae in the Complex Thalloid Liverworts (Marchantiales). It is poorly understood taxonomically and a worldwide revision of the c. 158 described species is badly needed. Its gametophyte is morphologically complex and rich in qualitative characters; the sporophyte is highly reduced but shows great diversity in spore ornamentation patterns. Marchantiales are among the earliest land plants but relationships and phylogeny are poorly understood.

A morphological taxonomic revision of available Eurasian material is presented, based on both field and herbarium studies. Cytological studies yield little useful data. Subgenera and sections are defined. Sixteen species are accepted and described in detail, along with keys to subgenera and species (including regional keys), full synonymy and typification, including designation of many new lectotypes. Spore ornamentation proved vital in identifying old fragmentary type specimens. For each species geography and ecology are summarised. Where appropriate, detailed notes on typification, nomenclature, synonymy, era, are given. Excluded taxa are listed and discussed.

The revision demonstrates a major advance in knowledge of Eurasian Asterella: extensive reduction in names due to past over-description; the existence of two undescribed species; the importance of characters such as sexual condition and spore ornamentation, and the plasticity of many quantitative characters; clarification of phytogeography with a number of localised endemics and several very widespread taxa.

Contents

Abstract 5
Introduction 5
Acknowledgements 6
Background and rationale 7
Historical review 10
Classification of Asterella within the liverworts 10
The family Aytoniaceae and its genera 17
Key to genera of Aytoniaceae 18
Plagiochasma 20
Reboulia 20
Mannia 21
Cryptomitrium 22
Asterella 22
Nomenclatural and taxonomic history of the genus Asterella 27
Asterella species worldwide 36
Review of Asterella species in the study area 38
Taxonomic characters 49
Morphology of Asterella 49
Vegetative features of gametophyte 49
Reproductive features of gametophyte 54
The sporophyte 48
Spore morphology 59
Introduction 59
Materials, methods and spore characters 62
Results of spore studies 66
Discussion of spore studies 71
Key to Asterella species using spore colour and SEM characters 76
Classification of Spore Types found in Eurasian Asterella species 78
Glossary of spore terminology 80
Taxonomic revision of Asterella in Eurasia 99
Materials and methods 99
Taxonomic account 107
Generic synonymy of Asterella 107
Notes on generic typification and orthography 108
Generic description of Asterella 109
Infrageneric groupings 112
Key to subgenera of Asterella in Eurasia 113
Keys to Eurasian species of Asterella 114
Species accounts 129
Subgenus Saccatae 129
1. Asterella saccata 129
2. Asterella grollei 138
Subgenus Wallichianae 144
3.Asterella wallichiana 144
Subgenus Asterella 159
4. Asterella africana 160
5. Asterella cruciata 164
6. Asterella khasyana 169
7. Asterella leptophylla 176
8. Asterella blumeana 183
9. Asterella limbata 186
Subgenus Phragmoblepharis 190
10. Asterella lindenbergiana 191
11. Asterella persica 197
12. Asterella pappii 200
13. Asterella mussuriensis 202
13a. Asterella mussuriensis subsp. mussuriensis 204
13b. Asterella mussuriensis subsp. crassa 206
14. Asterella multiflora 209
15. Asterella vulcanica 212
Subgenus Graciles 217
16. Asterella gracilis 218
Excluded taxa and doubtful records from Eurasia 226
Ecology 231
Distribution and phytogeography 231
Discussion and conclusions 232
Bibliography 233
Appendix:Eurasian Asterella specimens studies 258
Index of names 286

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