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Evolving to Invade

Marcia Angle Liz Schultheis Tomomi Suwa. Evolving to Invade. What is evolution?. A change in a trait of a population over time (generations). e.g. H air color Disease resistance Chemical compound Tail length . Frequency. Beak Depth. Large Ground Finch Geospiza magnirostris.

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Evolving to Invade

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  1. Marcia Angle Liz Schultheis Tomomi Suwa Evolving to Invade

  2. What is evolution? • A change in a trait of a population over time (generations). e.g. Hair color Disease resistance Chemical compound Tail length Frequency Beak Depth Large Ground Finch Geospizamagnirostris

  3. For evolution by natural selection to occur we need… • Variation in the trait • The trait has a genetic basis – is passed on to offspring • Some individual produce more offspring than others (i.e. Natural Selection) Individual birds Evolution of increased beak size! # offspring Beak Size

  4. Where does variation come from? • Mutation • Recombination • Migration

  5. Evolution by Natural Selection Trait: body color Selection agent: birds Evolution of body color! evolution.berkeley.edu

  6. At what level does evolution occur? • Individual • Population(a group of interbreeding individuals) • Species(a group of potentially interbreeding individuals – usually includes many populations)

  7. At what level does evolution occur? • Individual • Population(a group of interbreeding individuals) • Species(a group of potentially interbreeding individuals – usually includes many populations)

  8. What is an invasive species? • Introduced from another country by people • Grows and takes over an area • Can harm native species • Cost people a lot of time and money

  9. “Nothing in biology makes sense except in the light of evolution.” -Theodosius Dobzhansky (1973)

  10. Discussion: how will evolution affect a new invasive species? • Think back to the elements necessary for evolution to occur: • Variation • Trait is genetic and passed down from parents to offspring • Selection on the trait. Survival and ability to reproduce depends on trait value.

  11. Discussion: how will evolution affect a new invasive species? • There might be low genetic variation at first • But multiple introduction increases genetic variation • Invaders experience new selection in introduced range • Invaders evolve to adapt to a new environment

  12. Game: understanding evolution in a new invasive species • Our species – purpleloosetrife • Individual plants have seeds with different numbers of barbs, which predators can use to collect the seeds

  13. Trait Variation

  14. Game: Graph ___ ___ 10 9 8 7 6 5 4 3 2 1 Number of individuals in population 0 1 2 3 4 5 Trait Value (# of Velcro pieces)

  15. Selection on Trait Seed predator 1

  16. Game: Evolution in the native range 1 C 1 A 1 B 1 D Average trait = 3 2.5 2

  17. Selection on Trait Seed predator 2

  18. Game: Evolution in the invasive range 2 C 2 A 2 B 2 D Average trait = 2 3.4 2

  19. How did evolution affect our invasive species? • Low genetic variation at first in invasive range • Multiple introductions increased genetic variation • Invader experienced new type of selection in introduced range (from different type of predator) • Invader evolved and adapted to a new environment

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