THE SYSTEMATICS ASSOCIATION SPECIAL VOLUME No. 25 CURRENT CONCEPTS IN PLANT TAXONOMY Edited by VM^THEYWOOD and D. M. MOORE v/ Department of Botany, University of Reading, England 1984 Published for the SYSTEMATICS ASSOCIATION by ACADEMIC PRESS (Harcourt Brace Jovanovich, Publishers) LONDON ORLANDO UNIVERSITATS- B1BLIOTHEK SAN DIEGO! SAN FRANCISCO NEW YORK TORONTO MONTREAL SYDNEY TOKYO SAO PAULO
Contents List of Contributors Preface v vii Introduction The Current Scene in Plant Taxonomy v. H. HBYWOOD 3 Introduction 3 The rise of numerical taxonomy 4 New sources of taxonomic characters 6 1 Chromosome information cytotaxonomy 7 2 Chemical information - chemosystematics 8 3 Scanning and transmission electron microscopy - microcharacters 9 Biosystematics at the crossroads 10 Floristics 11 Taxonomic indexes and bibliographies 12 Symposia and conference volumes 12 Early evolution of the angiosperms 13 Systems of classification of higher taxa 14 Conclusions 15 References 15 Institutional Resources Libraries and Herbaria j. CULLEN \ 25 Introduction 25 Service to the user 26 Organization and reassessment of priorities 31 Conclusions 37 References 38 Botanic Gardens and Experimental Grounds p. s. ASHTON 39 Introduction 39 The divorce between systematics and living plants 40 The role of gardens in systematics 42 Conclusions 45 References 46
Contents Recent Approaches in Morphology and Anatomy Vegetative Morphology - Some Enigmas in Relation to Plant Systematics P. B. TOMLINSON 49 Introduction 49 Theoretical Considerations 51 1 Modular and unitary construction 51 2 Deterministic and opportunistic processes 52 3 Adaptive radiation offloralmechanisms 53 4 Correlation of characters 53 Architecture in systematics 55 1 Lack of systematic association 55 2 Woody monocotyledons 56 3 Shoot morphology 57 4 Seedling morphology 57 Neglected features 57 Structural and functional correlations 58 An evolutionary process 60 1 Evolutionary morphology of Tillandsia usneoides 61 Modular plasticity 63 1 Homology in modular organisms 63 Conclusion 64 Acknowledgements 65 References 65 The Taxonomic Importance of the Leaf Surface c. A. STACE 67 Introduction 68 The use of leaf-surface characters 69 Genetic control and phenotypic plasticity 71 Developmental studies 73 Evolutionary studies 74 Techniques 76 The leaf-surface characters 80 1 Trichomes 80 2 Venation systems 82 3 Epidermal cells 83 4 Stomata 85 5 Cuticular membrane 88 6 Epicuticular secretions 89 7 Special structures 90 Acknowledgements 90 References 90
Contents xi 6 Microstructural Features of Seed Surfaces w. BARTHLOTT 95 Introduction 95 Arrangement of seed-coat cells 97 Shape of cells: the primary sculpture 99 Fine relief of the cell wall: the secondary sculpture 101 Epicuticular secretions: the tertiary sculpture 102 Conclusions 102 Acknowledgements 103 References 104 7 Systematic Anatomy and Embryology - Recent Developments D. F. CUTLER 107 Introduction 108 Secondary xylem 108 Ultrastructure 114 Vascular systems 116 Nodal anatomy 116 Leaf vasculature 116 Epidermal studies 117 1 Plant surfaces 117 2 Stomata 117 3 Trichome types 118 The leaf 118 1 Morphology and development 118 2 Photosynthetic pathways 119 3 Sclereids 119 Floral studies 119 1 Stigmas 119 2 Nectaries and secretory tissues 120 3 Ligules 120 4 Petals 120 \ Seeds 120 Data banks and computer analysis 121 Embryology 121 1 Integuments 122 2 Ovules 123 3 Taxonomic applications 123 Major anatomical series of publications 124 Acknowledgements 125 References 125 8 Pollen Features and Plant Systematics s. BLACKMORE 135 Introduction 135 Some recent techniques in palynology 136
xii Contents Current approaches in palynology 141 1 Pollen Floras 141 2 Ontogenetic studies 141 3 Pollen form and function 145 4 Studies of unacetolysed pollen 149 5 Fundamental structure of the exine 150 Conclusions 151 Acknowledgements 151 References 151 Karyology and Genetics 9 Chromosomal Evidence in Taxonomy j. GREILHUBER 157 Introduction 158 Chromosome techniques 158 Heterochromatin 160 1 Heterochromatin variation 160 2 Chromosome banding as a tool in taxonomy 161 Euchromatin 171 Conclusions 175 Acknowledgements 175 References 175 10 Variation, Polymorphism and Gene-flow within Species Q. o. N. KAY 181 Introduction 182 Dioecy 183 Floral scent 185 Ultraviolet floral characters 186 Floral colour 191 Variation and gene-flow 195 References 196 Ecology and Geography 11 Infraspecific Variation and its Taxonomic Implications R. W. SNAYDON 203 Introduction 204 The nature of variation 205 The patterns of variation 206 1 The genetic pattern 206 2 The geographical pattern 206 3 Analysis of patterns 207
Contents xiii Magnitude of variation 208 Interspecific hybrids and gene-flow 209 The role of speciation 211 Infraspecific classification 212 Conclusions 214 References 215 12 Taxonomy and Geography D. M. MOORE 219 Introduction 219 The changing face of taxonomy 220 1 Morphology 220 2 Biosystematics 222 3 Phytochemistry 226 The changing face of geography 228 Whither now? 230 References 231 Chemistry, Taxonomy and Systematics 13 Chemical Data in Practical Taxonomy j. B. HARBORNE 237 Introduction 237 Newer chemical techniques 239 1 Analysis of low molecular weight constituents 239 2 Analysis of proteins and nucleic acids 242 Chemical identification of plant cultivars 243 1 Crop plants 243 2 Ornamental plants 247 Chemistry of plant hybrids 250 Chemistry in taxonomic revision 253 References 258 14 Phytochemistry in Plant Systematics and Evolution K. KUBITZKI 263 Introduction 263 Chemosystematic criteria 264 Chemistry in classification 265 Tracing evolution 268 Causes and mechanisms of phytochemical change 270 Conclusions 272 Acknowledgements 273 References 273
xiv Contents Data Processing and Taxonomy 15 Taximetrics To-day j. MCNEILL 281 Introduction 281 The nature of taximetrics 283 1 Phenetic classification and inumercal taxonomy 283 2 Objectivity: reality or illusion? 283 3 The scope of taximetrics 284 Taximetric methods and taxonomic purpose 285 1 Taximetric applications 285 2 Grouping of individuals 286 3 Hierarchical ordering of taxa 291 4 Continuous variation 294 5 Other taxonomic situations 294 Conclusions 295 Acknowledgements 296 References 296 16 Automated Taxonomic Information Systems F. A. BISBY 301 The dream 301 1 Information content 302 2 Information meaning 303 3 Floras, monographs and interconnections 306 4 Information services 306 The reality 307 1 Floristic projects 307 2 Monographic projects 309 Data structure 313 1 Character structure 314 2 Character formulation 316 3 Character selection 317 Data-base structure 317 Concluding remarks 319 Acknowledgements 320 References 320 17 Cladistic Methodology c. j. HUMPHRIES and v. A. FUNK 323 Introduction 324 Synapomorphies and homology 326 1 Approaches to systematics 326 2 Monophyletic groups 328 3 Parsimony 330
Contents. xv Criteria for assessing apomorphies 333 1 Common is primitive 333 2 Ontogeny 334 3 Out-group comparison 336 Homoplasy - parallelism and convergence 341 Reticulate evolution 343 Classification 346 Example 350 Conclusions 355 Acknowledgements 355 References 356 Taxonomic Priorities 18 Completing the Inventory G. T. PRANCE 365 Introduction 366 The problem of rare species in the tropics 368 The problem of neglected areas 377 What is inventory? 378 1 Special collections 379 2 Biological data 379 3 Quantitative inventory 380 4 Plant groups to be collected 382 5 Remote sensing 384 The written inventory and data processing 385 The deposition of specimens 386 Conservation and inventory 390 Acknowledgements 392 References 392 19 Designing Floras for the Future v. H. HEYWOOD 397 Introduction 397 Floras as front-line publications 401 Floras as data-bases 403 Floras and the consumer 404 Floras and the new technology 406 Conclusions 408 References 408 20 Taxonomic Problems Relating to Endangered Plant Species E. s. AYENSU 411 Subject Index 422 Systematics Association Publications 431