Patrick Meirmans, Hans den Nijs & Peter van Tienderen meirmans@science.uva.nl

1. Institute for Biodiversity and Ecosystem Dynamics Universiteit van Amsterdam The distribution areas of sexual and asexual dandelions suggest a postglacial recolonisation route for which there is only scarce genetic evidence. Patrick Meirmans, Hans den Nijs & Peter van Tienderen meirmans@science.uva.nl

2. Introduction: • Paradox of sex • Effect of parthenogenesis on the distribution of genetic variation

3. Dandelions(Taraxacum sect. Ruderalia)

4. Dandelions(Taraxacum sect. Ruderalia) • Two modes of reproduction: sex and parthenogenesis (apomixis) • Sexuals are diploid, apomicts are triploid • Both types can occur in mixed populations • Gene flow between sexuals and apomicts => constant generation of new apomictic lineages • Geographical parthenogenesis

5. 3x 3x 3x Distribution of reproductive types over Europe 2x & 3x 2x & 3x 3x 2x = Sexual, 3x = Apomict (Den Nijs & Sterk, 1981)

6. Geographical parthenogenesis • Apomicts all over Europe • Sexuals only in South, in two separate regions (East, West) • In East small morphological difference between sexuals and apomicts • In West no morphological difference between sexuals and apomicts

7. Research Questions: • Is the disjunct distribution pattern of the sexuals the result of postglacial recolonization from two refugia? • How is the genetic variation distributed between the sexuals and the apomicts? • Is there more differentiation between the sexuals and apomicts in the East than in the West (as the morphology suggests)?

8. 3x 3x 3x 3x 2x & 3x 2x & 3x Sample populations for chloroplast and microsatellite analyses

9. Diploids: Frt = 0.000 Triploids: Frt = -0.001 2x 3x 2x 3x Geographic differentiation: chloroplast haplotypes East - West (program: Fstat, Goudet, 2001) PCR-RFLP’s: intron trnL, trnl-trnF, psbA-trnH

10. axis2 (19%): Fst = 0.019 p = 0.001 axis1 (49%): Fst = 0.047 p = 0.001 PCA-analysis: Diploid Sexuals microsatellites Program: PCAgen (Goudet) Calculates Fst and associated p-value for every axis of a Principle Components Analysis 4 microsat loci 27 populations 548 individuals East - West Frt = 0.083 p = 0.001

11. axis2 (17%): Fst = 0.012 p = 0.053 axis1 (28%): Fst = 0.021 p = 0.003 PCA-analysis: Triploid Apomicts microsatellites Program: PCAgen (Goudet) Calculates Fst and associated p-value for every axis of a Principle Components Analysis 4 microsat loci 22 populations 360 individuals East - West Frt = 0.033 p = 0.001

12. Differentiation diploids vs triploids microsatellites • Diploid Sexuals (27 pops): Fst = 0.064 • East (12 pops): Fsr = 0.009 • West (9 pops): Fsr = 0.091 • Triploid Apomicts (22 pops): Fst = 0.093 • East (12 pops): Fsr = 0.032 • West (9 pops): Fsr = 0.063 • Diploids vs. Triploids (21 pops): Fpst = 0.063 • East (12 pops): Fpsr = 0.044 • West (9 pops): Fpsr = 0.087 (program: SPAGeDi, Hardy & Vekemans, 2002)

13. p=0.07 Differentiation diploids vs triploids microsatellites • Diploid Sexuals (27 pops): Fst = 0.064 • East (12 pops): Fsr = 0.009 • West (9 pops): Fsr = 0.091 • Triploid Apomicts (22 pops): Fst = 0.093 • East (12 pops): Fsr = 0.032 • West (9 pops): Fsr = 0.063 • Diploids vs. Triploids (21 pops): Fpst = 0.063 • East (12 pops): Fpsr = 0.044 • West (9 pops): Fpsr = 0.087 (program: SPAGeDi, Hardy & Vekemans, 2002)

14. Main results:chloroplasts and microsatellites • Chloroplasts: • No phylogeographic signal • Microsatellites: • Strongly significant differentiation between East and West • Almost all genetic variation shared between sexuals and apomicts • Eastern sexuals not more differentiated from apomicts than Western sexuals

15. Recolonisation hypothesis: • Chloroplasts: No • Microsatellites: Yes

16. This talk wouldn’t have been the same without: • Annemieke Kiers • Bas Reuvers • Hans Breeuwer • Jan Kirschner • Ludek Tikovsky • Marc Stift • Peter Kuperus • Piet Oosterveld • Rob Bregman • Ron van der Hulst • Steph Menken • Stephanie Hamm • Everybody at the Hugo de Vries-lab