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Evolutionary Aspects of Invasion

Evolutionary Aspects of Invasion. Overview. Summary of Papers General Themes Summary. Summary of Lee Paper: Evolutionary genetics of invasive species. Various genetic changes can improve a species ability to respond to natural selection, and consequently to adapt and invade.

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Evolutionary Aspects of Invasion

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  1. Evolutionary Aspects of Invasion

  2. Overview • Summary of Papers • General Themes • Summary

  3. Summary of Lee Paper: Evolutionary genetics of invasive species • Various genetic changes can improve a species ability to respond to natural selection, and consequently to adapt and invade. • Genetic characteristics, such as gene interaction, expression and rearrangement enable the evolutionary process. • Following invasion, evolutionary process continues, selecting in response to local environmental conditions and species.

  4. Summary of Mooney and Cleland: Evolutionary impact of invasive species • Evolutionary effects of changing biotas (species introductions, invasives). • Invaders respond evolutionarily in response to the new environment and the new species. • As evolution influences success of new species, the change in its abundance can also prompt the evolution of other community populations in response.

  5. Summary of Petit: Biological invasions at the gene level • Considering the gene rather than the species may be more informative and appropriate. • Exotic gene flow is not restricted to exotic seed flow.

  6. General Themes • 1. Genetics of Invasion • 2. Mechanisms for Evolution in Invasive Species • 3. Evolutionary Responses in Local Species

  7. 1. Genetics of Invasion • Broad Interpretation: • The more variation, the higher the chance of success, improved fitness • Genetic components of natural selection: • Additive genetic variance (AGV) • The proportion of variance that is due to the additive component of allelic effects • AGV is the most important component affecting selection because it predicts how well phenotype is transferred from parent to offspring • Additional explanation for observed tolerance and plasticity: • Copepod complex Eurytemora affinis • Observed lag time • Epistasis: interaction between gene loci resulting in a unique effect on phenotype Lee

  8. 1. Genetics of Invasion (cont…) • Genomic rearrangements: chromosomal inversions • Associated with temperature gradient, latitude • Fitness tradeoffs: various environments can create distinct races based on pre-existing fitness tradeoffs • Fly larvae, Rhagoletis pomonella • Influence of particular genes: one or a few genes can have great impact • Fire ant, Solenopsis invicta Lee

  9. 1. Genetics of Invasion (cont…) • Hybridization: • Increased genetic variation • new gene interactions • masking of deleterious alleles • acquisition of favorable genes Genetically engineered crops conveying herbicide resistance to non-crops. Lee, Mooney, Petit

  10. 1. Genetics of Invasion (cont…) • Gene flow in plants: • Pollen from the male estimated dispersal is an order of magnitude greater than seed flow. Though seed dispersal is limited to a degree; pollen flow is much less • Mix of foreign and local genes facilitates introduction of the invading genes • Hybrid soup: the many combinations • Inter- and intraspecific hybridization- both contaminate the local gene pool • Cryptic invasions: detectable? • European hazelnut, Corylus avellana • The case for considering the gene rather than the species regarding invasions Petit

  11. 2. Mechanisms for Evolution in Invasive Species • As a result of genetic variance, populations are able to evolve local adaptations to new environments- • Selection on dispersal (Butterfly, Pararge aegeria) and tolerance to site conditions • Once established, populations can evolve in response to • Local environmental conditions: Light, climate, pH • Resident species: predators, prey and competitors • crop mimic; predator release Lee

  12. 2. Mechanisms for Evolution in Invasive Species (cont..) • Respond with changes in: • Phenology (Goldenrods, Solidago altissima and S. Gigantea) • Morphology (fruit fly wing size cline) • Physiology • Plasticity (Velvetleaf, Abutilon theophrasti) Lee

  13. 3. Evolutionary Responses in Local Species • Traits change: soapberry bug, Jadera hematoloma • Behavioral change: Euphydras butterfly • Niche displacement: 250 new species in the Mediterranean Sea • Competitive exclusion • Mutualism • Host switching • Extinctions (Introgression, competitive exclusion…) Mooney

  14. Community Effects Possible Invasion Facilitators and Interactions Expansion/Invasion Increased AGV Local Population Gene Changes Introduction Hybridization Expansion/Invasion Establishment Increased AGV

  15. Questions How does the rate of species introductions affect the interactions and outcomes? How is the mixing of species and gene pools different than historic invasions (glacial retreat after the ice age, etc)? Are these evolutionary processes any different for native species? Non-invasives? If population genetics do affect the likelihood of invasiveness, what are the implications for predicting invasiveness? How does human activity influence the genetic structure of populations?

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