W12: Biocontrol (Videos & Theories Of Invasion) [Dr. Nic]

Question 1

Biological control attributes? (3)

Answer 1

• Is an applied science.
• Uses the “sky is blue” approach.
• Uses specialist insects & not generalist insects.

Question 2

The “sky is blue” approach attributes? (2)

Answer 2

• Often a way of presenting information that’s simple, straightforward & hard to dispute like “the sky is blue”.
• Implies sticking to the basics & presenting things as clearly & factually as possible without adding too much complexity that might be open to debate.

Question 3

Video 1 attributes? (4)

Answer 3

• Introduces biocontrol.
• Agent = cactiphagous.
• Biocontrol is more effective than chemical use (expensive).
• Biocontrol is self-sustaining & doesn’t need to be reintroduced.

Question 4

How are invasives around? (4)

Answer 4

• Boats, animal hides, bales of hay & ornamental plants are often how invasive plants are introduced.
• Some invasives are useful like prickly pear but they tended to become problematic.
• Most invasives are ornamental plants & grow easily.

Question 5

Egs of invasives? (2)

Answer 5

• Weeds.
• Cactus.

Question 6

Why were weeds & cactus problematic invasives?

Answer 6

It’s because of poor land management.

Question 7

Egs of useful invasives? (2)

Answer 7

• Prickly pear.
• Dragon fruit.

Question 8

What drives invasions/Theories of invasion? (40

Answer 8

• Enemy Release Hypothesis (ERH).
• Novel Weapons Hypothesis (NWH).
• Empty/Vacant Niche Hypothesis (ENH/VNH).
• Evolution of Increased Competitive Ability (EICA).

Question 9

ERH attributes? (3)

Answer 9

• Premise of biocontrol.
• Escape from natural enemies (predators, pathogens & competitors).
• Released from its natural enemies.

Question 10

NWH?

Answer 10

= suggests that invasive species bring unique traits/weapons (like allelopathic chemicals or other harmful traits) that native species in the new range have not encountered before, giving the invader an advantage.

Question 11

Who proposed the NWH? (2)

Answer 11

Callaway & Ridenour.

Question 12

Eg of the NWH?

Answer 12

Garlic mustard & fungal species.

Question 13

ENH/VNH attributes? (2)

Answer 13

• Suggests that invasive species succeed because they occupy a vacant/underutilised ecological niche in the new environment.
• Lack of competition allows the invader to thrive.

Question 14

EICA?

Answer 14

= suggests that once an invasive species has escaped its natural enemies, it reallocates its resources that would be used for defence towards growth, reproduction & competitiveness.

Question 15

EICA attributes? (3)

Answer 15

• Proposed by Blossey & Notzold (in particular to plants).
• Little good evidence for this.
• Graph it’s associated with.

Question 16

Explain EICA Graph? (8)

Answer 16

• Speaks to the investment of the invasive plant.
• x-axis = Population age.
• 2 points on x-axis = Invasion front & Core population.
• Invasion front means plant is now removed from native enemies.
• Core populations are native grounds.
• Positive/Increasing linear graph = from invasion front to cor populations, invasive plant has defense against generalists.
• Negative/Decreasing linear graph = from invasion front to core populations, invasive plant reallocates to growth, competitive effect (allelopathy) & dispersal ability.
• Constant dotted line = defence against specialist & competitive response.

Question 17

What is the underlying mechanism? (3)

Answer 17

• Flow chart of the theories of invasion.
• Ultimately, all these contribute to invasion & are dependent on the species & the environment.
• You can implement more than 1 theory to explain invasion.

Question 18

Explain the Invasion curve? (11)

Answer 18

• x-axis = Time.
• y-axis on left = Area infested.
• y-axis on right = Control costs.
• Sigmoid shape.
• Shifts around depending on the situation.
• From bottom to top: 1 = Introduction & prevention or eradication is simple.
• 2= Detection & eradication is feasible.
• 3 = Land managers aware of the problem.
• 4 = Eradication unlikely & intense effort is required.
• 5 = Public awareness typically begins.
• 6 = Local control & management only.