Biotic Resistance and Meltdown

Question 1

Biotic resistance hypothesis

Answer 1

Invasion are less likely to succeed in species-rich communities

Question 2

2 main problems with the biotic resistance hypothesis

Answer 2

• Does not distinguish invasibility and vulnerability to ecological impact
• does not account for propagule pressure

Question 3

What is the role of scale in biotic resistance?

Answer 3

Biotic resistance hypothesis tends to apply only on small scales. Larger scales tend to show the opposite - a positive correlation between species native and exotic species richness.

Question 4

Biotic resistance model

Answer 4

As invaders accumulation, space for more invasions becomes limited overtime. Therefore, it should be gradually more difficult for the next invaders due to decrease in vacant niches

Question 5

What is the opposite of the biotic resistance model?

Answer 5

Biotic facilitation - invasional meltdown. This is where facilitation between invasive species takes place.

Question 6

5 ways in which biotic facilitation can happen with examples

Answer 6

1. Animals pollinating and dispersing plants: introduced foxes in australia aid the spread of european weeds.
2. Animals modifying habitats: introduced water buffalo tramping create germination grounds for invasive mimosa seeds in australia.
3. Plants modifying habitats: Nitrogen fixating shrubs invade volcanic grounds, allowing the establishment of exotic plants in hawaii.
4. Addition of prey of host species: zebra mussels allowing the spread of their predator, the round goby in the great lakes.
5. Indirect effects: nonnative fish feed on native tadpoles, creating space for invasive bullfrog

Question 7

Invasional meltdown hypothesis

Answer 7

Positive interactions among non native species can increase their likelihood of colonization success and impact, such that there is a rapid accumulation of invaders and their synergistic effects.

Question 8

Commensalism definition

Answer 8

Describes a relationship in which one species profits and the other isn’t effected

Question 9

Ammensalism definition

Answer 9

Describes a relationship in which one species is negatively effected and the other isn’t effected at all

Question 10

Describe the invasional meltdown on Christmas Island

Answer 10

• The non-native “crazy ant” invaded the island. It has a negative effect on the native red land crab.
• The crazy ant has a mutualistic relationship with nonnative scale insects,
• The lack of red land crab and presence of scale insects has a positive effect on vegetation growth
• The presence of vegetation is positive for the nonnative giant snail, which also finds success due to disappearance of its predator, the red land crab.