Testing for rapid adaptation in fireweed

1. Testing for rapid adaptation in fireweed Andrew Lowe, Eleanor Dormontt, Peter Prentis Australian Centre for Evolutionary Biology and Biodiversity School of Earth & Environmental Sciences The University of Adelaide 28th May 2008

2. A sleeper weed • Lag phase between introduction and population explosion, may last generations • Range of ecological explanations • Demographic population increase • Release from native predators/herbivores • Change in climate – more suitable

3. A sleeper weed • Lag phase between introduction and population explosion, may last generations • Range of ecological explanations • Demographic population increase • Release from native predators/herbivores • Change in climate – more suitable • Genetic explanations for post introduction adaptation – well known in evolutionary biology but rarely considered for weeds • Prentis, Wilson, Dormontt, Richardson, Lowe (2008) TIPS

4. Genetic mechanisms of adaptation • Bottleneck • Admixture – multiple sources • Hybridisation • Gene expression and genome selection

5. Genetic mechanisms of adaptation • Bottleneck • Admixture – multiple sources • Hybridisation • Gene expression and genome selection ARC Discovery funded • Elly Dormontt – PhD • Peter Prentis & Skye Thomas Hall - Postdocs

6. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

7. Population "explosion" (Sindel & Michael 1988) End of lag phase (sensu Pyšek & Prach 1993) Spread dynamics • 1918 Hunter Valley

8. Spread dynamics 1948

9. Spread dynamics 1968

10. Spread dynamics 1988

11. Spread dynamics 2008

12. Spread dynamics

13. Spread dynamics Population boom circa 1983 post drought

14. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

15. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

16. Bottlenecks • Traditionally thought to constrain adaptation • Reduced quantitative variation • Under extreme inbreeding can get new genetic variants (hopeful monsters) • May allow adaptation to new environments

17. Bottlenecks • Traditionally thought to constrain adaptation • Reduced quantitative variation • Under extreme inbreeding can get new genetic variants (hopeful monsters) • May allow adaptation to new environments • Invasive Canary Island St John’s wort • Extreme bottleneck – locally adapted populations

18. Bottlenecks • Unlikely for fireweed • Mating system is outcrossing • biparental inbreeding • (Prentis et al 2007 New Phytologist) • High genetic variation in Hawaiian populations • Sourced from Australia (Le Roux 2008 Div&Dist)

19. Bottlenecks • Unlikely for fireweed • Mating system is outcrossing • biparental inbreeding • (Prentis et al 2007 New Phytologist) • High genetic variation in Hawaiian populations • Sourced from Australia (Le Roux 2008 Div&Dist) • Does not rule out bottleneck during early stages of Australian colonisation • Will genetically screen contemporary populations and herbarium specimens – bottlenecks, mating system

20. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

21. Novel gene combinations Admixture

22. Admixture Earlier genetic work by Radford and Scott et al indicate that Kwa-Zulu Natal is the likely source region of introduction for fireweed into Australia

23. Admixture Kwa-Zulu Natal East coast Australia • Conducting microsatellite analysis of dynamics of source introductions

24. Admixture Single source Kwa-Zulu Natal East coast Australia • Similar studies now done on range of species • Scotch broom, cats claw, bellyache bush

25. Admixture Multiple sources Kwa-Zulu Natal East coast Australia • Similar studies now done on range of species • Scotch broom, cats claw, bellyache bush

26. Admixture Multiple sources temporal spread Kwa-Zulu Natal East coast Australia • Analysis of contemporary populations and herbarium specimens to track introduction history

27. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

28. Hybridisation multiple outcomes Invasive Native Extinction e.g. Mercurialis annua Introgression e.g. Helianthus annuus ssp. texanus Speciation e.g. Senecio squalidus

29. Hybridisation • Hybridisation • Sample collections from hybrid zones with S. pinnatifolius Involucral bracts 18-21 = Senecio madagascariensis (Fireweed) 11-14 = Senecio pinnatifolius

30. Hybridisation • S. pinnatifolius Springbrook tableland variant (Prentis et al, New Phytol. 2007) S. pinnatifolius (native) S. madagascariensis (invasive) Hybrid native seed invasive seed capitula

31. Hybridisation • S. pinnatifolius Springbrook tableland variant (Prentis et al, New Phytol. 2007) S. pinnatifolius (native) S. madagascariensis (invasive) Undue influence by fireweed onlevel of hybridisation in native-asymmetric hybridisation Hybrid native seed invasive seed capitula

32. Hybridisation • S. pinnatifolius Springbrook tableland variant (Prentis et al, New Phytol. 2007) S. pinnatifolius (native) S. madagascariensis (invasive) No viable hybrids found at field site,hybrids are not developing and aretherefore gamete sink Hybrid native seed invasive seed capitula

33. Hybridisation • S. pinnatifolius Springbrook tableland variant (Prentis et al, New Phytol. 2007) S. pinnatifolius (native) S. madagascariensis (invasive) Hybrid native seed invasive seed capitula

34. Hybridisation • S. pinnatifolius Springbrook tableland variant (Prentis et al, New Phytol. 2007) S. pinnatifolius (native) S. madagascariensis (invasive) Hybrid native seed invasive seed capitula

35. Hybridisation multiple outcomes Invasive Native Extinction Introgression Speciation

36. Hybridisation • Mature hybrids found between fireweed and dune variant • Unknown hybrid outcome with headland variant • 3 sympatric sites sampled • Genetic analysis underway • Examine role of hybrids in history – herbarium survey

37. Genetic mechanisms of adaptation • Bottleneck – mating system, genetic diversity • Admixture – source of introduction • Hybridisation – introgression and demographic swamping • Gene expression and genome selection – Dynamics and rapid evolution of species

38. Gene expression and selectionExperimental strategy Landscape genomics Genetic maps Expressed genes isolated Quantification of which genes have changed expression -source (South Africa) and introduction (Australia) Candidate genes are screened for variation and evidence for genome selection Range of variable genes under selection ‘Weedy genes’

39. Summary of key findings • Mating system and population dynamics • Source of introduction – biocontrol source • History of introduction and mixing • Dynamics of hybridisation • Demographic swamping and/or introgression • Gene expression and genome selection • Selective response due to environment • Weedy genes, rapid adaptation and evolution

40. Acknowledgements • Drs Peer Schenk (UQ) and Tony Clarke (QUT) • Prof Dave Richardson and Dr John Wilson (Stellenbosch, South Africa) • Profs Richard Abbott (St Andrews, UK) and Loren Rieseberg (UBC)