Lecture 24

Question 1

What is a threatened species?

Answer 1

a plant or animal species with a population / pathway towards extinction

more than 32,000 species are threatened w extinction

Question 2

What are some extinction risks?

Answer 2

• small population size
  (possible Allee effects + low genetic diversity)
• small geographic ranges
• slow growing and reproducing
• narrow ecological niches

Question 3

What is an Allee effect?

Answer 3

a small population phenomenon in which population growth rate is reduced by undercrowding (low population density)

Question 4

What is the most commonly observed mechanism that causes an Allee effect?

Answer 4

Mate limitation - too few animals in an area to discover mates or too few plants close enough to achieve pollination

• can also occur through cooperative defense, predator saturation, cooperative breeding, cooperative feeding, or dispersal

Question 5

Pollination example (Allee effect)

Answer 5

• Tree has a typical dispersal range for its pollen
• when trees are clustered and population size is large, pollination occurs
• habitat loss causes population decline
• trees become less clustered - can no longer get pollinated bs they are too distant from neighbours

Question 6

What is inbreeding depression?

Answer 6

inbreeding may lower the population’s ability to survive and reproduce (occurs a lot in small populations as matings b/w relatives are common)

e.g. if one relative contains a deleterious recessive allele, inbreeding may increases the chances of that deleterious allele being expressed in the offspring

Question 7

What does lower genetic diversity lead to?

Answer 7

• lowered evolutionary potential
• compromised reproductive fitness
• elevates extinction risk

Question 8

What’s the problem with having small geographic ranges?

Answer 8

• species with SMALL geographic ranges have a higher rate of extinction
• small ranges expose species to greater threat of habitat loss as the threatening process may occur across the entire range of the species
• e.g. fires, storms, floods

Question 9

What’s the issue with having a narrow ecological niche?

Answer 9

• a narrow ecological niche means a species relies heavily on specific habitats or resources within an ecosystem

Question 10

Globally, what are the top 2 impacts on threatened species?

Answer 10

• habitat loss & change due to agriculture
• overexploitation activities, like hunting or timber harvesting

Question 11

In Australia, what are the top 2 impacts on threatened species?

Answer 11

• invasive species
• changes in habitat

Question 12

Which animals are more vulnerable to overexploitation?

Answer 12

• large, slow reproducing species (e.g. sharks)

Question 13

How do invasive species impact populations?

Answer 13

• via predation
• competition for space / resources
• by causing mortality through toxicity
• includes pest animals, plants, and diseases

Question 14

When are threats most impactful?

Answer 14

when the threats are ADDITIVE

Question 15

What is threat reduction?

Answer 15

• habitat restoration
• reducing exploitation levels
• removal of invasive species –> predators & competitors
• creation of reserves e.g. national parks

Question 16

How is population boosting done?

Answer 16

• captive breeding to increase population numbers before release back into the wild
• might be coupled with other strategies

Question 17

What is genetic rescue?

Answer 17

the process where inbred populations receive genes from another population such that their overall genetic diversity increases

• genetic diversity tries to solve the problem of inbreeding depression