What do we know about the genetics of invasiveness

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What do we know about the genetics of
invasiveness?
Baker (1965) listed 12 characteristics of an
ideal weed

• Germinable in many environments
• Long dormancy and discontinuous germination
• Rapid growth to flowering stage
• Long period of seed production
• Partially self-compatible
• Generalist cross-pollinator

7. High seed output 8. Environmentally tolerant
and phenotypically plastic 9. Short- and
long-distance dispersal 10. Vegetative
reproduction (for perennials) 11. Stem abscises
easily (for perennials) 12. Strong interspecific
competitor
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Baker (1965) also coined the term general
purpose genotype (gpg)
(develops through) evolutionary release from
restrictions on its range of tolerance of abiotic
environmental variation..
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Factors influencing the level of genetic
variation in populations (Barrett 1981)
Factor Influence Founder effect number and
types of immigrants Genetic drift frequency of
genetic bottlenecks Pop. age and size habitat
stability, life history features Degree of
sexuality cloning vs. sexual reproduction Mating
system level of inbreeding Hybridization gene
exchange w/ related taxa Environ.
Heterogeneity spatial, temporal habitat variation
Can we prioritize these (or make some kind of
expert system) to aid management decisions?
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A general outline of an invasion
One or a very few introductions
Limited genetic variability
Long lag time (selection, adaptation,
hybridization, etc, etc needed for new
environments)
Establishment, radiation and spread
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Possible indicators of invasiveness?
Amount of genetic variability
Availability of congeners for hybridization
OR
Probably lots of others.
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Can the advantages of genetic variability be
replaced by phenotypic plasticity?
The range of phenotypes expressed by a genotype
under various environments
Literature survey is there evidence for
adaptation or plasticity in successful invasions?

Three cases for adaptation Seven cases for
plasticity
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How is plasticity assayed?
Character state approach and/or norm of reaction
(polynomial) approach
What is the genetic basis of plasticity?
Two possibilities 1) Loci with
environmentally-based allelic sensitivity
2) Regulatory loci that alter gene expression
across environments
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Possible examples of plasticity genes
Heat shock genes
Phytochrome gene families
Sulfur limitation genes in Cyanobacteria
Temperature-dependent sex determination in
reptiles
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RiskBenefit Ratio