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What makes a species invasive? c) Micro-evolutionary change hypothesis

What makes a species invasive? c) Micro-evolutionary change hypothesis. Micro-evolutionary change hypothesis Frequent colonizing events are a central feature of invasive plants. What makes a species invasive? c) Micro-evolutionary change hypothesis. Micro-evolutionary change hypothesis

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What makes a species invasive? c) Micro-evolutionary change hypothesis

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  1. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events are a central feature of invasive plants

  2. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects = founders of a new population carry only a fraction of the total genetic variation of the source populations

  3. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks = loss of genetic variation when population size drastically decreases; often associated with catastrophic events that result in mass mortality

  4. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift = loss of genetic variation by chance when populations are small and do not have complete, random interbreeding

  5. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection: strong selective forces often apply to successful colonizers

  6. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment – rapid adaptive responses over short times and within short distances to new environment

  7. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment – shifts in relative proportions of competition vs. defense pressures

  8. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization – a natural process that occurs in plants

  9. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization – a natural process that occurs in plants • ↑ genetic diversity

  10. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization – a natural process that occurs in plants • ↑ genetic diversity • ↓reproductive barriers

  11. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization – a natural process that occurs in plants • ↑ genetic diversity • ↓reproductive barriers • Transfers or originates adaptations

  12. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization – a natural process that occurs in plants • 2834 plant species in the British Isles • Of these, 715 (25%) are hybrids • 74 are native X alien • 21 are alien X alien • 95 (13% of hybrids) involve aliens

  13. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization • Interspecific – often with other species in new environment

  14. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Micro-evolutionary change hypothesis • Frequent colonizing events • Founder effects • Genetic bottlenecks • Genetic drift • Natural selection • New abiotic environment • New biotic environment • Hybridization • Interspecific • Intraspecific – often with populations from native range that would not normally occur

  15. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Introgression = back cross with 1 or more parents • P1 X P2 → F1 • F1 X {P1, P2} → F2 introgressant

  16. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Introgression = back cross with 1 or more parents • Stabilized = viable, fertile hybrids

  17. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Hybrids form new Intraspecific taxa

  18. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Hybrids form new intraspecific taxa • Hybrids form new Species – Note: all examples are alien X alien

  19. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Allopolyploids = hybrid between different species in which chromosomes of both parents are retained

  20. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Hybridization Evidence: • Stabilized introgressants • Allopolyploids • Hybrids form new Species – Note: both Tragopogon’s are alien X alien

  21. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Rhododendron ponticum in British Isles • *Milne & Abbott (2000) Molecular Ecology 9:541-556 • Natural distribution: south of Black Sea with disjunct populations in Lebanon, Spain, & Portugal

  22. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Rhododendron ponticum in British Isles • *Milne & Abbott (2000) Molecular Ecology 9:541-556 • Natural distribution: south of Black Sea with disjunct populations in Lebanon, Spain, & Portugal • Extensively naturalized throughout British Isles

  23. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Rhododendron ponticum in British Isles • *Milne & Abbott (2000) Molecular Ecology 9:541-556 • Natural distribution: south of Black Sea with disjunct populations in Lebanon, Spain, & Portugal • Extensively naturalized throughout British Isles • Origin unclear: • Earliest known introduction (1763) from Spain • But subsequent introductions likely, especially from Black Sea area • Also can’t tell from morphological information where it came from, but know from morphology that had to hybridize at some time • R. ponticum cultivated along with other introduced species

  24. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study:Rhododendron ponticum in British Isles • *Milne & Abbott (2000) Molecular Ecology 9:541-556 • Most individuals from naturalized populations had genotypes from Spain (88%), followed by Portugal (10%) • No genotypes from Black Sea region

  25. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study:Rhododendron ponticum in British Isles • *Milne & Abbott (2000) Molecular Ecology 9:541-556 • Most individuals from naturalized populations had genotypes from Spain (88%), followed by Portugal (10%) • No genotypes from Black Sea region • Small number of individuals had hybridized with at least 3 other species • Occurrence of R. catawbiense genotypes most common in Scotland (coldest area of British Isle) • Introgression with catawbiense appears to have conferred cold tolerance into ponticum

  26. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Tamarix in US • *Gaskin & Schaal (2002) PNAS 99:11256-11259 • Native range: 54 species across Europe & Asia • Introduced range: originally 8-12 species into US for shade & for erosion control • 2 species particularly invasive: • Tamarix ramosissima & T. chinensis

  27. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Tamarix in US • *Gaskin & Schaal (2002) PNAS 99:11256-11259 • In native ranges: T. ramosissima & T. chinensis overlap • But different genotypes from DNA sequencing • T. chinensis: Haplotype 2 (red); primarily homozygous • T. ramosissima: Haplotype 1 (blue) most abundant, but also others; fewer homozygotes, many heterozygotes • No T. ramosissima -T. chinensis hybrids (red-blue combinations)

  28. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Tamarix in US • *Gaskin & Schaal (2002) PNAS 99:11256-11259 • In US: • ~20% genotypes are T. ramosissima homozygotes (blue-blue) • ~20% genotypes are T. chinensis homozygotes (red-red) • ~20% genotypes are T. ramosissima -T. chinensis hybrids (red-blue) • Also get novel genotypes plus hybrids with other Tamarix species

  29. What makes a species invasive? • c) Micro-evolutionary change hypothesis • Case Study: Tamarix in US • *Gaskin & Schaal (2002) PNAS 99:11256-11259 • In US: • ~20% genotypes are T. ramosissima homozygotes (blue-blue) • ~20% genotypes are T. chinensis homozygotes (red-red) • ~20% genotypes are T. ramosissima -T. chinensis hybrids (red-blue) • Also get novel genotypes plus hybrids with other Tamarix species • Complicates biological control efforts in US

  30. What makes a species invasive? • c) Micro-evolutionary change hypothesis • SUMMARY: Micro-evolutionary change hypothesis • Likely that most (if not all) invasive species go through founder events, experience genetic bottlenecks & drift, and undergo selection • In other words micro-evolutionary changes • Good evidence for hybridization being beneficial

  31. What makes a species invasive? • c) Micro-evolutionary change hypothesis • SUMMARY: Micro-evolutionary change hypothesis • Likely that most (if not all) invasive species go through micro-evolutionary changes • Good evidence for hybridization being beneficial • But • Have evidence of micro-evolutionary changes for only a limited number of species • For only a subset of these, have evidence that micro-evolutionary changes have been beneficial • A species that undergoes micro- (or even macro-) evolutionary changes does not automatically become invasive

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