Genetic erosion and pollution - genetic and conservation consequences

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

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

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

4. Ne = 30 Ne = 7 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 =  => no evolution constant Ne => stable evolution Ne decreases => erosion accelerates

5. human impact 1. General concepts and processes: genetic erosion 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 (Nunney, 2000)

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

7. 1. General concepts and processes: balanced effects demographic swamping migration load reduce Ne demographic rescue increase diversity reduce inbreeding restoration extinction 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)

8. 2. Specific features for trees

9. annual trees plants nb species 196 226 mean nb pop. 9.2 18.1 mean nb loci 18.1 16.2 He (total div. )0.177 0.154 Hs (within-pop div. )0.148 0.101 Gst (differentiation)0.084 0.355 2. Specific features for trees : high diversity in spite of recent colonization history, high diversity is generally maintained within tree populations (Hamrick et al, 1992)

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

11. h² AGCV (sA/m %) (Cornelius, 1993) height 0.28 11.10 straightness 0.28 16.25 morphol. traits 0.23 14.73 wood density 0.50 5.34 branch 0.26 16.30 (Ducousso,unpubl.) phenology 0.30 23.73 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

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

13. Ne=31 Ne=83 Ne=85 Ne=59 700 7743 7822 584 Ne=92 Ne=57 Ne=36 Ne=76 2210 398 7787 45719 2. Specific features for trees : temporal patterns erosion of diversity is delayed by temporal patterns of fecundity: annual stochasticity reduces the impact of selection, cumulative effect reduces drift (Krouchi et al, 2004)

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 response function 142 pop Pinus contorta tested on 60 sites (Rehfeldt et al, 2001)

15. date 2. Specific features for trees : rapid adaptation tree populations have the potential for rapid adaptive changes ... % budset in Norway spruce (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. 3. Consequences for management: global perspective Habitat monitoring Environmental impact Population management environment landscape wild relative domestic resource interactions

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. 3. Consequence for management : geneticpollution 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 ; (adapted from Wolf et al, 2001)

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

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

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