Plant Variation and Evolution

by David Briggs , Stuart Max Walters

• ISBN13: 9780521459181
• ISBN10: 0521459184
• Edition: 3rd
• Format: Paperback
• Copyright: 1997-11-28
• Publisher: Cambridge University Press

Summary

Natural populations of plants show intricate patterns of variation. European botanists of the eighteenth and nineteenth centuries used this variation to classify different "kinds" into a hierachy of family, genus, and species. Although useful, these classifications were based on a belief in the fixity of species and the static patterns of variation. Darwin's theory of evolution changed this view; populations and species varied in time and space and were part of a continuing process of evolution. The development of molecular techniques has transformed our understanding of microevolution and the evolutionary history of the flowering plants. This revised, extended edition describes the historical background to plant variation studies and considers the remarkable insights that molecular biology has recently given into the processes of evolution in populations of cultivated, wild and weedy species; the threats of extinction faced by many endangered species and the wider evolutionary history of the flowering plants as revealed by cladistic methods.

Table of Contents

Preface to the Third Edition	xv
Acknowledgements	xix
Note on names of plants	xxi
Looking at variation	1	(6)
`Kinds', species and natural classification	1	(4)
Individual variation	5	(1)
The nature of species	5	(2)
From Ray to Darwin	7	(26)
Ray and the definition of species	7	(2)
The Chain of Being	9	(1)
Linnaeus	10	(7)
Buffon and Lamarck	17	(3)
Darwin	20	(9)
Tests of specific difference	29	(4)
Early work on biometry	33	(19)
Commonest occurring variation in an array	35	(1)
Estimates of dispersion of the data	36	(2)
Histograms, frequency diagrams and the normal distribution curve	38	(3)
Other types of distribution	41	(1)
Comparison of different arrays of data	42	(1)
Complex distributions	43	(3)
Local races	46	(2)
Correlated variation	48	(2)
Problems of biometry	50	(2)
Early work on the basis of individual variation	52	(28)
Phenotype and genotype	53	(2)
Transplant experiments	55	(3)
The work of Mendel	58	(6)
Pangenesis	64	(1)
Mendelian ratios in plants	65	(1)
Mendelism and continuous variation	66	(7)
Physical basis of Mendelian inheritance	73	(7)
Post-Darwinian ideas about evolution	80	(8)
Experimental investigation of evolution	80	(4)
The mutation theory of evolution	84	(1)
Neo-Darwinism	85	(3)
Modern views on the basis of variation	88	(36)
Molecular basis of heredity	88	(6)
Mutation	94	(4)
Cytological differences	98	(4)
Non-Mendelian inheritance	102	(1)
Modern techniques used in studying genetic variation	103	(1)
Electrophoretic studies of enzymes	104	(3)
Analysis of DNA	107	(4)
Use of DNA in studies of variation	111	(3)
Patterns of variation	114	(1)
Phenotypic variation	114	(2)
Developmental variation	116	(4)
Phenotypic plasticity	120	(4)
Breeding systems	124	(43)
Outbreeding	124	(9)
Late-acting self-incompatibility systems	133	(1)
Self-fertilisation	133	(1)
Apomixis	134	(9)
Consequences of different reproductive modes	143	(2)
Advantage and disadvantages of different breeding systems	145	(3)
Breeding systems in wild populations	148	(9)
Environmental control of facultative apomixis	157	(1)
The use of molecular markers in the study of the reproductive behaviour of apomictic plants	158	(2)
Evolution of breeding systems	160	(5)
Concluding remarks	165	(2)
Infraspecific variation and the ecotype concept	167	(41)
Turesson's pioneer studies and other experiments	167	(7)
Experiments by American botanists	174	(9)
The widespread occurrence of ecotypes	183	(1)
Clines	183	(3)
Factors influencing the variation pattern	186	(4)
The refining of genecological experiments	190	(1)
Sampling populations	190	(6)
Cultivation experiments	196	(5)
The designed experiment	201	(5)
The interpretation of experiments	206	(2)
Recent advances in genecology	208	(51)
Variation in populations	209	(2)
Plant populations	211	(1)
Gene flow	212	(1)
Gene flow: early ideas	212	(1)
Gene flow: agricultural experiments	213	(2)
Gene flow: insights from the movement of pollen	215	(2)
Gene flow: studies of seed dispersal	217	(1)
Gene flow: studies using molecular tools	218	(3)
`Neighbourhoods' in wild populations	221	(2)
Effects of chance	223	(2)
Founder effects in introduced species	225	(1)
Selection in populations	226	(2)
Fitness	228	(1)
Studies of single factors	228	(1)
Studies of several interacting factors: Lotus and Trifolium	229	(8)
Reciprocal transplant experiments	237	(2)
Experimental evidence for disruptive selection	239	(5)
Co-selection in swards	244	(1)
The speed of microevolutionary change: agricultural experiments	244	(2)
Rapid change in polluted sites	246	(4)
Microevolution in arable areas	250	(2)
Adaptive and non-adaptive characters	252	(3)
Patterns of variation in response to seasonal or irregular extreme habitat factors	255	(2)
Concluding remarks	257	(2)
Species and speciation	259	(11)
The species concept	259	(1)
Other species definitions	260	(3)
Gradual speciation	263	(1)
Abrupt speciation	264	(6)
Gradual speciation and hybridisation	270	(39)
Evidence for gradual speciation	271	(1)
Crossing experiments with species of Layia	272	(1)
The interpretation of crossing experiments	273	(1)
Studies of Layia using molecular methods	274	(2)
Uncertainties about the concept of gradual speciation	276	(1)
Natural hybridisation	277	(7)
The consequences of hybridisation: some theoretical considerations	284	(3)
Results of disruptive selection in polymorphic populations	287	(3)
Introgression and other patterns of hybridisation	290	(5)
Genetic investigations of hybridisation	295	(2)
Chemical studies of hybridisation	297	(2)
Critical tests of the hypothesis of introgression	299	(3)
Recent studies of introgression using molecular tools	302	(2)
Introgression in Louisiana Irises	304	(3)
Concluding remarks	307	(2)
Abrupt speciation	309	(52)
How common is polyploidy?	309	(3)
Experimental studies of polyploids	312	(1)
Early cytogenetic studies	312	(1)
Resynthesis of wild polyploids	313	(1)
Auto- and allopolyploidy	314	(4)
Genome analysis	318	(4)
Genome analysis: uncertainties about ancestry	322	(3)
Genetic control of chromosome pairing: the implications for genome analysis	325	(2)
Studies of karyotypes	327	(3)
Chemical studies	330	(1)
Autopolyploids: reassessment of their evolutionary potential	331	(1)
Polytopic multiple origin of polyploids	332	(6)
The origin of new polyploids: the role of somatic events and unreduced gametes	338	(2)
The persistence of polyploids	340	(4)
Gene flow between diploids and polyploids	344	(2)
Polyploids: their potential for evolutionary change	346	(2)
Distribution of polyploids	348	(3)
How important is polyhaploidy?	351	(1)
The delimitation of taxa within polyploid groups	351	(1)
Abrupt speciation	352	(1)
Changes in chromosome number	353	(4)
Chromosome repatterning	357	(1)
Speciation following hybridisation	358	(1)
Minority disadvantage	359	(2)
The species concept	361	(6)
The biological species concept	362	(2)
The views of botanical taxonomists	364	(3)
Evolution: some general considerations	367	(32)
The fossil record	368	(2)
Diversification of the angiosperms	370	(2)
Microevolution and macroevolution	372	(7)
The devising of phylogenetic trees	379	(3)
The use of computers in taxonomy	382	(2)
The influence of numerical taxonomy	384	(1)
Cladistics	385	(4)
A critique of cladistic approaches	389	(7)
Transgenic plants	396	(3)
Conservation: confronting the extinction of species	399	(35)
What are the threats to biodiversity?	400	(1)
What classes of evidence are available for assessing claims concerning threats of extinction?	400	(2)
The threats induced by changes in land use	402	(1)
Threats to native biota from introduced plants and animals	402	(2)
The effects of pollution	404	(2)
How many species are there in the world?	406	(2)
How many species are threatened with extinction?	408	(3)
Processes involved in the extinction of species	411	(1)
Demographic stochasticity	412	(2)
Effects of fragmentation	414	(1)
Genetics of small populations	414	(2)
Minimum viable populations	416	(3)
What priorities should be set in attempting to reverse the decline of endangered species?	419	(2)
Ex situ conservation	421	(2)
The role of protected areas in countering the threat of extinction	423	(3)
Managing resources to prevent extinction of species	426	(1)
Restoration ecology	427	(1)
Manipulating and creating populations of endangered species in an attempt to prevent extinction	428	(4)
Arguments for conservation	432	(2)
Glossary	434	(4)
References	438	(61)
Index	499