Lecture 10: Biotic Resistance

Question 1

Explain the biotic resistance hypothesis

Answer 1

• resistance by the resident community against the establishment of non native sp
• this is esp important for post established success
• basically communities that are rich in diversity will be able to better resist invasions than those lower in species richness

Question 2

What evidence supports the biotic resistance hypothesis/

Answer 2

• simplified communities (oceanic islands and crop monocultures) are susceptible to pests

Question 3

What are the problems with the biotic resistance hypothesis?

Answer 3

• confusion between community invisibility and vulnerability to impact
• does not take into account differences in propagule pressure

Question 4

Why are controls important for looking at the biotic resistance hypothesis?

Answer 4

• bc various factors could positively impact both native and non native sp
• ex: species area effects: larger areas get more sp, more niches, more refuge, more resources etc BOTH native and non natives will respond to that

Question 5

Explain Elton’s Hypothesis

Answer 5

• extrinsic environmental factors may create a positive correlation between native and exotic species richness
• *means both native and invasive sp will respond the same, which means whatever relationship is seen could be based on what they are sharing

Question 6

Talk about scale effects

Answer 6

• local scale: overcrowding, resource avail, light -> crowding and competition are important here
  L> that is the scale you see resistance of establishment and post establishment success

Question 7

What is the relationship between native and exotic species richness are large scales?

Answer 7

• thye ar positively correlated
• extrinsic factors (climate, latitude, nutrients) support different levels of total species richness over larger spatial scale s

Question 8

Explain the biotic resistance model

Answer 8

• species rich communities may use available resources more fully
• contain a variety of consumers that limit the number of host species that can invade
• THEREFORE membership is increasingly limited over time

Question 9

What do case studies suggest about aquatic systems and community diversity?

Answer 9

• all aquatic systems are invasible and inability is not necessarily related to resident diversity
  Ex: Lake Victoria is really high in diversity (nile perch are up a lot of endemic sp, diversity in sp doesn’t mean there is good richness overall, fish were small tc) and invasions of tropical reefs

Question 10

Explain the effect of diversity on the invasion success of zooplankton in ponds

Answer 10

• both the biomass of exotics and proportion of successful introductions declined with diversity of native species increasing

Question 11

In the stages of invasions where is biotic resistance most important?

Answer 11

• During Introduction (with geographic barrier, physiological barrier, demographic barrier, biotic resistance)
• during establishment (physiological and biotic resistance)
• during population expansion (physiological barrier and biotic resistance)

*AKA it impact throughout the invasion

Question 12

Explain the relationship between the P/A of blue crabs and it’s impact on green crabs?

Answer 12

• when blue crabs are present , there are less green crabs present

Question 13

Propagule pressure and disturbance can interact to over come?

Answer 13

• biotic resistance of marine invertebrate communities

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Question 14

Explain why there is stronger biotic resistance in tropical regions

Answer 14

• there is higher diversification in native app and therefore higher biotic resistance