Genetic analysis of aspen (Populus tremula L. and Populus tremuloides Michx.) in a diversity experiment

,

• Publisher: Cuvillier Verlag
• Year: 2012
• Print ISBN: 9783954042043
• eBook ISBN: 9783736942042
• Edition: 1

Poplars are model tree species in ecological and genetic studies since they arewidely distributed, easy to propagate, and since more genetic and genomic resources areavailable for poplars than for any other woody plant genus. The poplar diversityexperiment (POPDIV) has been established with European and North American aspen(Populus tremula L., P. tremuloides Michx.) planted in plots representing either a singledeme only or combinations of two, four and eight demes in order to test the influence ofintraspecific genetic diversity on ecosystem functions and services. In the present study, the most commonly used molecular markers, SSRs (simple sequence repeats) and AFLPs(amplified fragment length polymorphisms), were applied to conduct the genetic analysisof the POPDIV experiment. Both markers identified clonal structures in one Swedishdeme and these clones are non-randomly distributed in the POPDIV experimental field.Large differences with regard to the genetic diversity within aspen demes were observed.The genetic diversity estimates based on SSR and AFLP markers showed a highcorrelation. The North American P. tremuloides deme had the highest level of geneticdiversity; most private alleles both at SSRs and AFLPs were also observed in this demewhich confirmed that it represents another species different from the European P.tremula. An analysis of molecular variance (AMOVA) revealed that most of the totalgenetic diversity was found within demes by both SSR and AFLP markers, but thegenetic differentiation among demes was also high. Pairwise FST values between demesshowed highly significant differentiation at both SSRs and AFLPs. As expected, theP. tremuloides deme was strongly differentiated from the other P. tremula demes.UPGMA dendrograms based on genetic distances obtained from both markers showedthat the North American P. tremuloides deme is obviously outgrouped from the otherEuropean P. tremula demes with high bootstrap support values. The complex patterns ofgenetic diversity and differentiation resulted in large differences of the genetic variationwithin plots. Genetic diversities within plots with a given number of demes were highlyvariable. Across all plots, those with a single German deme and those with two demesshowed the lowest and highest level of genetic diversity, respectively. The plotscontaining the North American P. tremuloides deme showed higher levels of geneticdiversity compared to the plots including only P. tremula demes, which was obviouslyshown at AFLPs. For the plots with a given number of demes (1, 2, 4, 8), their averagegenetic diversity values were increased with increasing number of demes included withinplots. However, the genetic variation within plots strongly depended on the specificmixture, and the highest diversities were observed for plots with only two demes mixed.Paternity analysis revealed different numbers of paternal trees contributed to bothGerman single tree progenies, the deme with a high number of pollen donors showedhigh level of genetic diversity. The sibship reconstruction revealed a higher number offull sibling groups for the North American P. tremuloides deme compared to otherdemes. Across demes, the genetic diversity revealed by AFLP markers showed a positivecorrelation with the number of full sibling groups, indicating that the number of fullsibling groups reflects the effective number of population size which directly determinesthe level of genetic diversity. In conclusion, the high and variable levels of geneticdiversity observed within all demes need to be considered in assessments of the impact ofintraspecific diversity of poplars on the diversity of the associated organisms andecosystem functions and services. The genetic diversity in a plot strongly depends on thespecific combination of demes; the number of demes included within a plot is a poorpredictor of its diversity.

Table of contents

• ACKNOWLEDGEMENTS
• TABLE OF CONTENTS
• 1 INTRODUCTION
• 2 MATERIALS AND METHODS
• 3 RESULTS
• 4 DISCUSSION
• 5 CONCLUSIONS AND OUTLOOK
• 6 SUMMARY
• 7 ZUSAMMENFASSUNG
• 8 REFERENCES
• 9 APPENDICES
• CURRICULUM VITAE