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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. - PowerPoint PPT Presentation
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Evolving to Invade
Marcia AngleLiz SchultheisTomomi Suwa
A change in a trait of a population over time (generations). e.g.
Hair colorDisease resistanceChemical compoundTail length Fr
eque
ncy
Beak Depth
Large Ground FinchGeospiza magnirostris
What is evolution?
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)
# off
sprin
g
Beak Size
Individual birds
Evolution of increased beak
size!
Where does variation come from? Mutation Recombinatio
n Migration
Evolution by Natural Selection
evolution.berkeley.eduEvolution of body
color!
Trait: body colorSelection agent: birds
At what level does evolution occur?
• Individual• Population (a group of interbreeding individuals)• Species (a group of potentially interbreeding
individuals – usually includes many populations)
• Individual• Population (a group of interbreeding individuals)• Species (a group of potentially interbreeding
individuals – usually includes many populations)
At what level does evolution occur?
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
“Nothing in biology makes sense except in the light of evolution.”
-Theodosius Dobzhansky (1973)
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.
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
Discussion: how will evolution affect a new invasive species?
Game: understanding evolution in a new invasive species Our species – purple
loosetrife Individual plants have
seeds with different numbers of barbs, which predators can use to collect the seeds
Trait Variation
Game: 10987654321
0 1 2 3 4 5
Num
ber o
f ind
ivid
uals
in p
opul
atio
n
Trait Value (# of Velcro pieces)
Graph ___ ___
Selection on Trait
Seed predator 1
Game: Evolution in the native range1 A 1 B 1 D
Average trait =
2.5 2
1 C
3
Selection on Trait
Seed predator 2
2 A 2 B 2 D
Average trait =
3.4 2
2 C
Game: Evolution in the invasive range
2
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
How did evolution affect our invasive species?