Repeated Evolution of Highly Metal Tolerant Ecotypes in Alyssum montanum L.

About this book

Language: English with bilingual abstract in English and German

The author describes the adaptation to metal contaminated soils of various populations of Alyssum montanum L. (Brassicaceae) by conducting a large scale tolerance experiment, cytotype characterization, population genetic analyses and an exploratory genome scan. Metalliferous soils are a challenge for plant life as they force species to develop tolerance mechanisms to prevent toxic effects of metal ions. Therefore, plants adapted to metalliferous soils provide model systems for examining edaphic adaptation and its role in the formation of ecotypes as well as ecological speciation.

A. montanum was proven to be a pseudometallophyte (plants that can tolerate a high metal content in their environment, but also thrive under normal conditions). Among populations different degrees of metal tolerance have been observed, ranging from metal sensitive to highly metal tolerant. Metal tolerance repeatedly evolved in various populations, whereby the tolerance is specific to the soil metal composition of the population site. Similar metal tolerance and similar differentiation in candidate loci in tolerant diploid and tetraploid populations indicate a parallel evolution of metal tolerance across cytotypes. Furthermore, populations of non-metal sites are probably able to develop tolerance within a short time period. Evidence was found for a local or even microgeographic adaptation in both cytotypes. These findings offer the opportunity for subsequent analyses to explore genetic architecture of metal tolerance and reproductive isolation in a non-model species in connection with edaphic differentiation.

Contents

List of tables 6
List of figures 8
List of abbreviations 10

1. Introduction 11
2. Material and methods 21
      2.1 Sampling and investigated populations 21
      2.2 Cytotype characterization 28
            2.2.1 Chromosome counts 28
            2.2.2 Flow cytometry 28
      2.3 Tolerance experiment 30
            2.3.1 Experimental design and procedure 30
            2.3.2 Soils and soil analysis 31
            2.3.3 Data analysis 32
      2.4 AFLP analysis 33
            2.4.1 Choice of method 33
            2.4.2 Sampling and DNA isolation 34
            2.4.3 AFLP fingerprinting 34
            2.4.4 Population genetic analyses 36
            2.4.5 Loci associated with metal tolerance 41
3. Results 43
      3.1 Cytotype characterization 43
            3.1.1 Chromosome counts 43
            3.1.2 Flow cytometry 44
      3.2 Tolerance experiment 46
      3.3 AFLP analysis 61
            3.3.1 Population genetic analyses 61
            3.3.2 Loci associated with metal tolerance 86
4. Discussion 100
      4.1 Cytotype characterization 100
      4.2 Metal tolerance of Alyssum montanum populations 100
      4.3 Population genetic analyses 105
      4.4 Loci associated with metal tolerance 113
      4.5 Concluding discussion 121
5. Abstract 124
6. Zusammenfassung 126
7. References 126
8. Appendix 147
9. Acknowledgements 195

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