4: Invasive species

Question 1

Describe what happened to Stephens Island Wren

Answer 1

• Flightless, endemic to Stephens Island, NZ
• 1984 built a lighthouse, lighthouse owned 1 cat
• Cat drove them to extinction
• Cats established thereafter, driven to extinction after ~40 yrs

Question 2

Describe Pacific Island extinctions

Answer 2

Mostly wholly or partly due to introduced predators: Cats, rats, pigs, snakes

Diseases e.g avian malaria
Hunting my man
Habitat conversion

Question 3

Describe the natural experiment on the island of Guam

Answer 3

Brown tree snake introduced
Near-complete loss of native forest birds by late 1980s

CONSEQUENCES:
Snake introduced, predates birds
Drives birds to near extinction
Birds (seed dispersers)
Seeds knocked out of food chain
Tree seeds unable to disperse

Question 4

Describe the consequences of the introduction of Avian Malaria to Hawaii

Answer 4

→ extinction of bird pollinators due to Avian Malaria
- 52 endemic species at European contact in Hawaii
- 50 years later 1/3 gone extinct and many others critical
Severe consequences:
- Cascading effects: extinction of 31 species of Hawaiian Lobelia in the last century (due to extinction of pollinators)

Question 5

Define introduced species

Answer 5

= lives outside native range
= Arrives by human activity
Deliberate e.g garden plant
Accidental e.g ballast in ships

Question 6

Why do Europe, North America and Australasia have unexpectedly high numbers of species (not proportional to their land area)?

Answer 6

Legacy of colonial activities
Current role as importers

= Abundance of introduced species

Question 7

Define invasive species

Answer 7

= introduced species that spread to:
Damage environ
Economy
Human health

(So, all invasives are ‘introduced species’, but not all introduced species are invasive)

Question 8

Describe the Chytrid fungus and its impact on ecosystems

Answer 8

• Fungal disease that affects the skin permeability of frogs and toads, leads to death in 21 days in 70% of cases
  = caused widespread amphibian loss
• Study on snakes in Panama found majority of species declined after chytrid = due to loss of food source
• Increase in some species (who don’t eat ~just~ amphibians) due to competitive release

Question 9

Describe the introduction of Nile Perch to Lake Victoria and its effects

Answer 9

• 50s Nile Perch introduced, explosive increase in pop. in 80s
• Large mussle mass and fighting fish made them perfect for competitive fishing
• Local communities relied for food and brought tourism

BUT, ~200 species of endemic chichlids estimated to have been driven to extinction by Nile Perch

Question 10

Give 2 examples of stopping introduction of invasives

Answer 10

E.g Burmese Python in Florida
E.g Western Australia has the strictest biosecurity laws on the planet

Question 11

Give examples of the eradication of invasives

Answer 11

E.g goats on the Galapagos, cropped the land and had impact on fauna
Paid people to go and kill the goats, ‘Judas’ Goats
Cost increases as pop. gets smaller as they’re much harder to find

E.g Rodents on Oceanic Islands
Rats eat chicks in the nests
Intensive trapping, blanket poisoning

Question 12

Describe local control of invasives + example

Answer 12

Limited resources or infestation preclude eradication
Control by reducing density:
- Manual (digging, pulling)
- Mechanical (cutting, girdling)
- Prescribed fire
- Chemical control (pesticides, herbicides)
- Biological control (grazers, introductions??)

e.g Scotch Broom removal, Milo McIver State Park, US