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

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

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What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Micro-evolutionary change hypothesis

  • Frequent colonizing events are a central feature of invasive plants


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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

  • Climate matching = different genetic stock succeed in different parts of introduced range; often correspond to similar latitudes or climate in native range. e.g. tamarisk in US.


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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

      • e.g.. Bearded Goatgrass in CA: ‘competitive’ VS ‘seed producing’ phenotypes in invasion front VS monoculture.


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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 vs. reproductive pressures e.g. Leger 2003.


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


Determining genetic change and hybridization

Determining genetic change and hybridization

  • How?


Determining genetic change and hybridization1

Determining genetic change and hybridization

  • How?

  • Morphology and cytology

  • Genetic analyses – chloroplast, nuclear, ribosomal DNA

  • Experiments (common garden)


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Hybridization Evidence:

  • Stabilized introgressants

    • Introgression = back cross with 1 or more parents

    • Stabilized = viable, fertile hybrids


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Hybridization Evidence:

  • Stabilized introgressants

    • Hybrids form new Intraspecific taxa


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Hybridization Evidence:

  • Stabilized introgressants

    • Hybrids form new intraspecific taxa

    • Hybrids form new Species – Note: all examples are alien X alien


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Hybridization Evidence:

  • Stabilized introgressants

  • Allopolyploids = hybrid between different species in which chromosomes of both parents are retained


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Hybridization Evidence:

  • Stabilized introgressants

  • Allopolyploids

    • Hybrids form new Species – Note: both Tragopogon’s are alien X alien


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Specific Example: 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Specific Example: 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Specific Example: 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) Micro-evolutionary change hypothesis

  • Specific Example: 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


Another example tamarisk in us

Another example: Tamarisk in US

  • Gaskin and Shaal 2002. PNAS 99 (17): 11256-11259

  • Used DNA sequencing to determine origins and relationships of plants (nuclear gene intron)

  • Little similarity in genetic types between US and Eurasia (4 common of 58 types)

  • Most common species in US invasion was hybrid between 2 Eurasian species (Tamarix chinensis and Tamarix ramosissima)

  • Hybrid unknown in Asia (species geographically isolated)


Evidence for genetic change in invasive species

Evidence for genetic change in invasive species

  • Leger and Rice 2003, Eschultzia californica

  • Used common garden to look for genetic VS phenotypic traits

  • Plants from Chile (invaded range) were larger with no competitors


What makes a species invasive f micro evolutionary change hypothesis

Leger and Rice 2003. Ecology Letters


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • f) 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


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species are immigrants to a new area

  • Aliens often arrive as seeds


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species are immigrants to a new area

  • Aliens often arrive as seeds

    • In other words, they arrive without the grazers, insect pests, diseases, parasites, etc. of their native range – their “enemies”


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species immigrate without enemies

  • Hence, alien species “escapes” from their enemies and are no longer affected by biotic constraints

    • Thus, alien growth and success is much greater in new range


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species immigrate without enemies

  • Aliens lack biotic constraints

  • However, alien success will depend on potential enemies in new range:

    • Are potential enemies generalists or specialists?


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species immigrate without enemies

  • Aliens lack biotic constraints

  • However, alien success will depend on potential enemies in new range:

    • Are potential enemies generalists or specialists?

    • Are population sizes of potential enemies large or small?


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species immigrate without enemies

  • Aliens lack biotic constraints

  • However, alien success will depend on potential enemies in new range:

    • Are potential enemies generalists or specialists?

    • Are population sizes of potential enemies large or small?

    • Do potential enemies feed on foliage or seeds?


What makes a species invasive f micro evolutionary change hypothesis

  • What makes a species invasive?

    • g) Escape from biotic constraints hypothesis

  • aka“Escape from enemy” hypothesis

  • “Enemy release” hypothesis

  • Basic concepts:

  • Species in their native range are suppressed by natural enemies

  • Alien species immigrate without enemies

  • Aliens lack biotic constraints

  • However, alien success will depend on potential enemies in new range:

    • Are potential enemies generalists or specialists?

    • Are population sizes of potential enemies large or small?

    • Do potential enemies feed on foliage or seeds?

    • Are there similar hosts for potential enemies in new area?


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