Section 1: Evolution and Ecology are Intertwined
- Theory of Evolution → conceptual foundation of all life sciences
- Theodosius Dobzhansky
- Modern understanding of evolution
- “Nothing makes sense except in the light of evolution” → including ecology
- Ecology → study of how organisms interact with each other and their environment .
- Includes population growth, competition, herbivory and predation.
- Evolutionary Biology → study of the process that lead to change in the genetic composition
of populations over generations
- Including speciation, extinction, and adaption
- Biologists thought that evolutionary and ecology processes were totally different
- Evolution was responsible for producing the organism ecologists study but no
measurable evolutionary changes were going to happen when an ecologists watching
- This traditional view was WRONG
- Evolution can be startlingly fast often occurring within a few generations
- Evolution is often facilitated by ecological processes and the ecological impacts that
result can be profound.
- Both biologist pay attention to each others discoveries
- Rapid Evolution of Resistance in a Crop Pest
- Pink Bollworms are major pest of cotton → hated by farmers
- On their own they cause no problems
- However they eat the flowers and seeds of cotton plants, reducing their fiber
productions
- And they stain any fibers infested plants do manage to make, diminishing the crops
commercial value
- Thought to be native to south or southeast Asia → Reached the US as an invasive
species in 1917. Since then impact has been severe
- The worst of it has been estimated to cost farmers nearly 80% of the value of a given
year’s cotton crop
- One of the reasons why this is such a serious pest is because of its capacity for
explosive population growth. A single female can lay between 100 to 200 eggs. Can
go through five generations during one single growing season.
- Traditional methods for controlling pink bollworm outbreak includes setting traps
baited with pheromones, releasing pink bollworm moths sterilised by irradiation, and
spraying fields with chemicals insecticides.
- Chemical insecticides have many drawbacks but are effective. One important
drawback is that pink bollworm populations exposed to chemical insecticides evolve
resistance
- 1996 → Bollgard: a cotton variety genetically engineered to produce its own
biological insecticide.
- Created by borrowing a gene from a bacterium called Bacillus thuringiensis
or Bt and spliced it into a cotton plant’s genome.
- The borrowed gene encodes a protein called Bt toxin Cry1Ac → harmless to
most animals but poisonous to larvae of butterflies and moths.
- When swallowed by a caterpillar, the toxin binds to molecules of a protein
called cadherin in the membranes of the caterpillar’s midgut cells. Triggers a
series of events that disrupt the caterpillar digestion and kill it
, - Unlike non-transgenic cotton transgenic cotton makes it own Bt toxin is
much less susceptible to infestation by pink bollworm
- It was discovered that in fields sprayed with chemical insecticides the same
number of times, transgenic plants yielded more cotton per acre than
non-transgenic plants.
- The value of the extra more than offset the added expense of buying Bollgard
seeds. Explains why transgenic cotton became so populars
- However the use of all of these caused grave concern
- Insecticides based on organic molecules were more specific in their effects
and though still toxic to humans they were less dangerous to work with. This
early optimism soon faded.
- One Major Drawback: The pest populations evolve across generations,
quickly becoming resistant to the insecticides’ effects.
- About three decades after 1980 hundreds of species rapidly evolved
resistance.
- Everyone in the industry is aware of the same risk as three species of moths
have already evolved to resist
- Bruce Tabashnik Experiment:
- Started his lab pink Bollworms with individuals collected from
commercial cotton fields.
- Some founders came from populations that had been exposed to Bt
toxin outdoors. All of the founders had survived at least small doses
of Bt toxin in the lab.
- Once the population was well established the selection experiment
began.
- He fed the pink bollworm wheat germ treated with Bt toxin. Just over
20% of the caterpillars survived. The survivors were left to mature
and breed.
- Then fed the next generation wheat germ and treated them with the
same dose of Bt toxin.
- The next generation also survived. How?
- The few individuals carried a rare mutation for the gene that codes
for the cadherin protein. These individuals just happen to be able to
survive exposure to Bt toxin.
- Initially rar can quickly become rare.
- Two Conclusions were drawn from this experiment: (1) Pink
bollworms are capable of evolving resistance to Bt toxin. (2)
Populations can evolve very quickly. One generation in the
experiment went from 20% resistance to 100% resistance.
- Rapid Evolution of Link in the Food Chain
- Rapid evolution is indeed common in nature and is often facilitated by ecological
phenomena such as predation.
- Lake Washington is home to a population of threespine sticklebacks.
- Not entirely defenseless, have bony plates in their skin that serve as armour
- Some wear full, some wear half, some wear minimal.
- More armour plating gives better protection against cutthroat but comes with
costs
, - Completely armoured fish survive winter at lower rates, and breed later. Due
to the fact that they grow slowly they can be more susceptible to predators.
- Populations in nature can evolve rapidly enough to change the ecological
interactions between species.
- Focused on evolution by Natural selection, but it actually involves multiple
different mechanisms of evolutions all of which can be happening at the ame
time.
- Evolution of Invasive Species
- The four mechanisms of evolution can occur simultaneously within a single
population, but they can also interact in interesting and ecologically relevant ways.
- Evolution by one mechanism can facilitate or hinder evolution by another.
- When species move to a new location they sometimes thrive to the point of disrupting
native communities or interfering with human activities.
- Eg. Ragweed Genus (Ambrosia)
- Moved to other continents but native to Americas
- Major cause of seasonal allergies
- Some invasive species have also become agriculture weeds
- When it moved to Japan 100 years ago it left behind one of its natural
enemies .
- It was suspected this escape resulted in selection for changes in ragweed’s
growth and reproduction → changes that contributed to the pants ecological
success as an invasive species
- Evolution Plays a Role in Ecology and Vice Versa.
- In all the examples presented the ecological and evolutionary processes strongly
influence each other.
- Predation and herbivory are both ecological phenomena as well as mediators of
genetic change within populations over generation.
- These examples demonstrate that ecology and evolution would be challenging to
understand separate/
- Mechanisms that make evolution happen → natural selection, migration, mutation,
and genetic drift.
-
Lecture One Notes:
- Fitness refers to The evolutionary success of an individual in an environment
- Specific to a given environment
- More evolutionary success
- Reproduction is heightened.
- Genetic contribution to the gene pool in all future generations
- Evolution can be rapid
- 3 examples were covered of evolutions that occurred on ecologically relevant time
scales
- Pink Bollworms
- Three Spined Stickleback
- Evidence of trade-offs between growth and defence in ragweed
- Japanese ragweed grew taller than North American ragweed after
80 days of growth but ragweed leaf beetles survived better on
- Theory of Evolution → conceptual foundation of all life sciences
- Theodosius Dobzhansky
- Modern understanding of evolution
- “Nothing makes sense except in the light of evolution” → including ecology
- Ecology → study of how organisms interact with each other and their environment .
- Includes population growth, competition, herbivory and predation.
- Evolutionary Biology → study of the process that lead to change in the genetic composition
of populations over generations
- Including speciation, extinction, and adaption
- Biologists thought that evolutionary and ecology processes were totally different
- Evolution was responsible for producing the organism ecologists study but no
measurable evolutionary changes were going to happen when an ecologists watching
- This traditional view was WRONG
- Evolution can be startlingly fast often occurring within a few generations
- Evolution is often facilitated by ecological processes and the ecological impacts that
result can be profound.
- Both biologist pay attention to each others discoveries
- Rapid Evolution of Resistance in a Crop Pest
- Pink Bollworms are major pest of cotton → hated by farmers
- On their own they cause no problems
- However they eat the flowers and seeds of cotton plants, reducing their fiber
productions
- And they stain any fibers infested plants do manage to make, diminishing the crops
commercial value
- Thought to be native to south or southeast Asia → Reached the US as an invasive
species in 1917. Since then impact has been severe
- The worst of it has been estimated to cost farmers nearly 80% of the value of a given
year’s cotton crop
- One of the reasons why this is such a serious pest is because of its capacity for
explosive population growth. A single female can lay between 100 to 200 eggs. Can
go through five generations during one single growing season.
- Traditional methods for controlling pink bollworm outbreak includes setting traps
baited with pheromones, releasing pink bollworm moths sterilised by irradiation, and
spraying fields with chemicals insecticides.
- Chemical insecticides have many drawbacks but are effective. One important
drawback is that pink bollworm populations exposed to chemical insecticides evolve
resistance
- 1996 → Bollgard: a cotton variety genetically engineered to produce its own
biological insecticide.
- Created by borrowing a gene from a bacterium called Bacillus thuringiensis
or Bt and spliced it into a cotton plant’s genome.
- The borrowed gene encodes a protein called Bt toxin Cry1Ac → harmless to
most animals but poisonous to larvae of butterflies and moths.
- When swallowed by a caterpillar, the toxin binds to molecules of a protein
called cadherin in the membranes of the caterpillar’s midgut cells. Triggers a
series of events that disrupt the caterpillar digestion and kill it
, - Unlike non-transgenic cotton transgenic cotton makes it own Bt toxin is
much less susceptible to infestation by pink bollworm
- It was discovered that in fields sprayed with chemical insecticides the same
number of times, transgenic plants yielded more cotton per acre than
non-transgenic plants.
- The value of the extra more than offset the added expense of buying Bollgard
seeds. Explains why transgenic cotton became so populars
- However the use of all of these caused grave concern
- Insecticides based on organic molecules were more specific in their effects
and though still toxic to humans they were less dangerous to work with. This
early optimism soon faded.
- One Major Drawback: The pest populations evolve across generations,
quickly becoming resistant to the insecticides’ effects.
- About three decades after 1980 hundreds of species rapidly evolved
resistance.
- Everyone in the industry is aware of the same risk as three species of moths
have already evolved to resist
- Bruce Tabashnik Experiment:
- Started his lab pink Bollworms with individuals collected from
commercial cotton fields.
- Some founders came from populations that had been exposed to Bt
toxin outdoors. All of the founders had survived at least small doses
of Bt toxin in the lab.
- Once the population was well established the selection experiment
began.
- He fed the pink bollworm wheat germ treated with Bt toxin. Just over
20% of the caterpillars survived. The survivors were left to mature
and breed.
- Then fed the next generation wheat germ and treated them with the
same dose of Bt toxin.
- The next generation also survived. How?
- The few individuals carried a rare mutation for the gene that codes
for the cadherin protein. These individuals just happen to be able to
survive exposure to Bt toxin.
- Initially rar can quickly become rare.
- Two Conclusions were drawn from this experiment: (1) Pink
bollworms are capable of evolving resistance to Bt toxin. (2)
Populations can evolve very quickly. One generation in the
experiment went from 20% resistance to 100% resistance.
- Rapid Evolution of Link in the Food Chain
- Rapid evolution is indeed common in nature and is often facilitated by ecological
phenomena such as predation.
- Lake Washington is home to a population of threespine sticklebacks.
- Not entirely defenseless, have bony plates in their skin that serve as armour
- Some wear full, some wear half, some wear minimal.
- More armour plating gives better protection against cutthroat but comes with
costs
, - Completely armoured fish survive winter at lower rates, and breed later. Due
to the fact that they grow slowly they can be more susceptible to predators.
- Populations in nature can evolve rapidly enough to change the ecological
interactions between species.
- Focused on evolution by Natural selection, but it actually involves multiple
different mechanisms of evolutions all of which can be happening at the ame
time.
- Evolution of Invasive Species
- The four mechanisms of evolution can occur simultaneously within a single
population, but they can also interact in interesting and ecologically relevant ways.
- Evolution by one mechanism can facilitate or hinder evolution by another.
- When species move to a new location they sometimes thrive to the point of disrupting
native communities or interfering with human activities.
- Eg. Ragweed Genus (Ambrosia)
- Moved to other continents but native to Americas
- Major cause of seasonal allergies
- Some invasive species have also become agriculture weeds
- When it moved to Japan 100 years ago it left behind one of its natural
enemies .
- It was suspected this escape resulted in selection for changes in ragweed’s
growth and reproduction → changes that contributed to the pants ecological
success as an invasive species
- Evolution Plays a Role in Ecology and Vice Versa.
- In all the examples presented the ecological and evolutionary processes strongly
influence each other.
- Predation and herbivory are both ecological phenomena as well as mediators of
genetic change within populations over generation.
- These examples demonstrate that ecology and evolution would be challenging to
understand separate/
- Mechanisms that make evolution happen → natural selection, migration, mutation,
and genetic drift.
-
Lecture One Notes:
- Fitness refers to The evolutionary success of an individual in an environment
- Specific to a given environment
- More evolutionary success
- Reproduction is heightened.
- Genetic contribution to the gene pool in all future generations
- Evolution can be rapid
- 3 examples were covered of evolutions that occurred on ecologically relevant time
scales
- Pink Bollworms
- Three Spined Stickleback
- Evidence of trade-offs between growth and defence in ragweed
- Japanese ragweed grew taller than North American ragweed after
80 days of growth but ragweed leaf beetles survived better on
