1. Genetic erosion and pollution - genetic and conservation consequences for European forest tree species François Lefèvre INRA, Avignon (France)

2. Non-equilibrium paradigm for in situ management of long lived species Conclusion population size genetic diversity current adaptedness are not stable nor ideal quantities, => think in terms of parameter changes and evolutions just instantaneous values resulting from dynamic processes Monitoring evolutionary changes Conservation of genetic resources

3. 1. General concepts and processes 2. Specific features for trees 3. Consequences for the management of genetic resources

4. 1. General concepts and processes: genetic erosion Ne, effective population size a standardized measure of genetic evolution (decrease of diversity or increase of inbreeding) unit : size of a model population that follows the same genetic evolution Ne = 7 Ne = 30 Ne =  =>no evolution constant Ne =>stable evolution Ne decreases=>erosion accelerates

5. Departure from the model population that decreases Ne: Biology - true or partial dioecy - departure from panmixia (both directions) Demography - variation in population size across generations - variance (V) in mating success - generation overlap Environment - selection human impact 1. General concepts and processes: genetic erosion (Nunney, 2000)

6. Hybridization (intra + interspecific) Natural Anthropogenic Type 1Type 3Type 2 Natural hybrid Natural introgression Natural hybrid zone Type 4Type 5Type 6 Hybridization no introgression Widespread introgression Complete admixture (sterile F1) F1 onlyHybrid swarm (backcrosses) (Allendorf et al, 2001) 1. General concepts and processes: hybridization-introgression

7. restoration extinction 1. General concepts and processes: balanced effects risk of extinction  if : local taxon is not rare reproductive barriers are strong long generation time selfing or vegetative propagation differencial selection is enhanced (Lenormand, 2002) demographic swamping migration load reduce Ne demographic rescue increase diversity reduce inbreeding

8. 2. Specific features for trees

9. in spite of recent colonization history, high diversity is generally maintained within tree populations annual trees plants nb species196226 mean nb pop.9.218.1 mean nb loci18.116.2 He (total div. ) 0.1770.154 Hs (within-pop div. ) 0.1480.101 Gst (differentiation) 0.0840.355 2. Specific features for trees : high diversity (Hamrick et al, 1992)

10. adaptive cline in sessile oak (Ducousso et al, 1996) in spite of recent colonization history, local adaptation rapidly developped through selection … 2. Specific features for trees : local adaptation...

11. 2. Specific features for trees : local adaptation & diversity in spite of recent colonization history, local adaptation rapidly developped through selection … and high diversity for adaptive traits is maintained within tree-pops h² AGCV (  A /  ) (Cornelius, 1993) height0.2811.10 straightness0.2816.25 morphol. traits0.2314.73 wood density0.50 5.34 branch0.2616.30 (Ducousso, unpubl.) phenology0.3023.73

12. the high diversity is explained by important seed and pollen dispersal, the long juvenile phase increases migration and reduces the founder effect expected at founding a new deme 2. Specific features for trees : important gene flow (Mariette, 2001) (Austerlitz et al, 2000)

13. 700 4571977873982210 58478227743 erosion of diversity is delayed by temporal patterns of fecundity: annual stochasticity reduces the impact of selection, cumulative effect reduces drift Ne=31 Ne=92 Ne=76Ne=36Ne=57 Ne=59Ne=85Ne=83 (Krouchi et al, 2004) 2. Specific features for trees : temporal patterns

14. 2. Specific features for trees : adaptational lag adaptation is a dynamic process where selection is balanced by gene flow (migration load), interaction among species (Red Queen hypothesis) and temporal fluctuations of environment (Rehfeldt et al, 2001) response function 142 pop Pinus contorta tested on 60 sites

15. 2. Specific features for trees : rapid adaptation tree populations have the potential for rapid adaptive changes... % budset in Norway spruce date (Skroppa & Kohman, 1997)

16. 2. Specific features for trees : climate change present tree populations and the next 1 or 2 generations will experience climate change within their own life : short phenotypic plasticity term adaptation long term migration

17. 3. Consequences for management of genetic resources

18. domestic resource wild relative interactions Population management Environmental impact Habitat monitoring environment landscape 3. Consequences for management: global perspective

19. 3. Consequence for management : genetic erosion domestication (breeding and selection) :  not a major threat for diversity in trees,  except if low initial diversity population management :  direct impact on demographic parameters (life cycle, dispersal, mating system, survival, mating success)  should not affect the processes that maintain a high level of diversity within tree populations (Lefèvre, 2004)

20. introduction, fragmentation and habitat disturbance influence hybridization risk assessment :  assess hybridization, occurrence and frequency (difficult) ;  estimate variation in frequency among cohorts ;  estimate the relative fertility of local and hybrid types reduce the impact of hybridization if considered as a risk :  eliminate hybrids and invading sp ;  improve habitat to enhance competition ; 3. Consequence for management : genetic pollution (adapted from Wolf et al, 2001)

21. genetic diversity highlow low high maladaptedness local pop. large Ne genetic diversity highlow low high local pop. small Ne hypoth.: large amount of transplanted material involved in the regeneration maladaptedness can be avoided but low diversity more likely higher impact when local population has small Ne 3. Consequence for management : genetic pollution (Lefèvre, 2004)

22. Non-equilibrium paradigm for in situ management of long lived species Conclusion population size genetic diversity current adaptedness are not stable nor ideal quantities, => think in terms of parameter changes and evolutions just instantaneous values resulting from dynamic processes Monitoring evolutionary changes Conservation of genetic resources

23. References Allendorf et al, 2001 TREE 16, 613-622 Austerlitz et al, 2000 Genetics 154, 1309-1321 Cornelius, 1993 Can J For Res 24, 372-379 Ducousso et al, 1996 Ann Sci For 53, 775-782 Hamrick et al, 1992 New Forests 6, 95-124 Krouchi et al, 2004 For Ecol Manage 197, 181-189 Lefèvre, 2004 For Ecol Manage 197, 257-271 Lenormand, 2002 TREE 17, 183-189 Nunney, 2000 Evol Biol 32, 179-194 Rehfeldt et al, 2001 Climatic Change 50, 355-376 Skroppa & Kohman, 1997 Forest Genetics 4, 171-177 Wolf et al, 2001 Conserv Biol 15, 1039-1053