Does disturbance matter?

1. Does disturbance matter? A landscape genetic approach for Lobaria pulmonaria Silke Werth Jesse M. Kalwij Daniela Csencsics Carolina Cornejo Christoph Scheidegger

2. Outline 1. This is landscape genetics 2. Genetic footprints of historic stand-replacing disturbances - Loss of genetic diversity - Bottlenecks 3. Quantifying gene flow at landscape level - Spatial autocorrelation - Patterns of genetic differentiation 4. Conclusion

3. Landscape genetics is … • a combination of population genetics and landscape ecology Landscape genetics can… • explain spatial genetic patterns by using landscape variables • to infer patterns of gene flow at landscape scale • to correlate genetic boundaries with landscape features Manel et al. (2003). TREE 18:189-199

4. Lobaria pulmonaria The model species' distribution in Switzerland L. pulmonaria Study area Stofer et al (2003): SwissLichens.

5. Disturbances in pasture-woodlands • Selective logging 2. Forest fires 3. Extensive cattle grazing

6. Sampling design • 250 random plots (1 ha)  L. pulmonaria demes • Mapping (J.M. Kalwij) • L. pulmonaria • potential host trees (Acer pseudoplatanus, Fagus sylvatica) • disturbed and undisturbed areas

7. Spatial distribution of L. pulmonaria 250 randomly selected plots = demes J.M. Kalwij

8. Historic disturbances • Reconstruction of two areas affected by stand-replacing historic disturbances (J. Bolli & J.M. Kalwij) • Logging, windthrow and fire (1871) • Charcoal production (1850 - 1900)

9. Historic disturbances East: No known stand-replacing disturbances North: Logging, windthrow and fire West: Charcoal production J. Bolli & J.M. Kalwij

10. Molecular-genetic analyses 842 individuals sampled in 40 demes 181 multilocus genotypes (=clones) - 6 polymorphic microsatellite loci* - indel of 2 bp in the ITS region** - all markers mycobiont-specific * marker development: Walser et al. (2003) FUNG GEN BIOL 40 ** based on sequences in: Zoller et al. (1999) MOL ECOL 8

11. Did the historic disturbances leave a genetic footprint in the demes? • Population bottleneck • Loss of rare alleles • Loss of rare multilocus genotypes • Loss of genetic diversity • This can be seen in allele and genotype maps

12. Locus LPu27 Loss of rare alleles in disturbed demes This pattern was also reflected in loss of rare genotypes and diversity

13. Bottlenecked to Ne=8 for 4 generations Bottlenecked to Ne=8 for 4 generations Not bottlenecked Proportion of alleles Allele frequency class Bottleneck effects in disturbed demes? Theoretical expectation Loss of rare alleles Following Luikart et al. (1998) J HEREDITY 89

14. Allele frequency class Disturbed demes (North) bottleneck evidence

15. East(no known stand-replacing disturbances) bottleneck-like pattern

16. Resumé • Evidence for recent bottlenecks in most disturbed demes • Bottleneck-like allelic distribution also in some demes not affected by the two historic disturbances

17. Do these bottlenecks matter? • If gene flow occurs only at the spatial scale of demes: - yes • Therefore, analyse the spatial scale of gene flow and the genetic differentiation among areas and demes

18. Molecular diversity Range estimate: genetic patch size Distance [m] Spatial scale of gene flow:Molecular diversity variogram Most gene flow occurs at short distances, i.e. up to 100 m Wagner et al. (in rev.) GENETICS

19. Genetic differentiation I: Analysis of molecular variance • No differentiation among areas • Strong differentiation among demes (FST=0.488) • The formation of new demes might be at random from the region's gene pool ( no diff. among areas) • Within each area, demes might be differentiated due to genetic drift.

20. Genetic differentiation II: Boundaries to gene flow North North East East West West Manni et al. (2004) HUM BIOL 76

21. Genetic differentiation II: Boundaries to gene flow North North East East West West Monmonier algorithm; software BARRIER Manni et al. (2004) HUM BIOL 76

22. Conclusion (I): Do the bottleneck effects matter? • Even though many demes are bottlenecked, the region still has a high genetic diversity. • Genetic differentiation among demes, but not among areas indicates that new demes are founded by propagules from the entire region.

23. Conclusion (II): Do the bottleneck effects matter? • Thus, as long as there is a large enough source in the region providing diaspores, inbreeding will not be a problem.

24. Thanks to Felix Gugerli, Susan Hoebee, Rolf Holderegger This research is funded by NCCR Plant Survival, Swiss National Foundation. … and YOU for listening!

25. Range of L. pulmonaria soredia: shared multilocus genotypes Genotype shared between two plots Gt 95 p=0.0020 Gt 139 p=0.000026 Gt 136 p=0.0000072 Probability of origin by recombination ≤ 0.002

26. Resumé • Origin of shared multilocus genotypes by recombination is unlikely • Most multilocus genotypes (159) in only one deme  short dispersal distance of soredia • Maximum distance between occurrences of a genotype ~2 km

27. Further evidence of clonal origin: • No sequence polymorphism in algal ITS rDNA cluster • However, one should look at more variable loci, and at a larger number of specimen Investigated specimens: Gt 139 (10 thalli from 3 demes) Gt 136 (3 thalli from 3 demes) a specimen eachfrom Norway and Germany for comparison

28. Is deme size important? (1) Each square represents a deme Gene diversity Deme size

29. How important is disturbance, and the history of demes? Charcoal production Genetic diversity Fire

30. Resumé: H1) Genetic diversity increases with deme size - deme size matters only in small demes. H2) Genetic diversity is higher in undisturbed than in disturbed demes - accepted in fire-disturbed area, rejected in area used for charcoal production.

31. North East West Frequency Allele frequency class Larger scale No bottleneck evidence