Lecture 13: The Ecological Naivete Hypothesis

Question 1

What up with Stephen’s island?

Answer 1

• endemic flightless bird, X. lyalli
• lighthouse keeper had a cat
• cat started killing them
• easy to hunt bc couldn’t fly
• activity time matched the cats
• more cats were introduced via ships keeping rats in check
• bird are now completely extinct
• introduced cats cause more species loss events on islands than mainland (have more sp and likely one similar to cats, also meta populations )

Question 2

Marine iguana example?

Answer 2

• killed by cats and rats

Question 3

What’s reptile diversity like on islands invaded by rats?

Answer 3

• low

Question 4

Whats going on with some islands with introduced rats having negligible impacts on birds and reptiles?

Answer 4

• bc some have native rats or something like land crabs which were predating on birds and reptiles SO when a rat or cat is introduced there are a already similar predators

Question 5

Explain the ecological naivete hypothesis

Answer 5

• impact of an invader on native species richness depends on the naivete of the invaders community
  i. e. it’s evolutionary history with functionally similar species

Question 6

What examples did we go through for ecological naivete?

Answer 6

1. Predation
2. Herbivory
3. Competition
4. Disease

Question 7

Predation examples?

Answer 7

1. effects of exotic trout on frogs in alpine lakes in California
   - lakes were fishless
   - tadpole has 2 year life stage, no predators naturally around so it’s safe
   - introduced fish, crops them own
2. Brown Tree Snake of Guam
   - arboreal, nocturnal
   - native to Indonesia
   - invaded Guam
   - extinctions of birds, lizards and bats
3. Nile perch introduced to Lake Victoria
   - decline in cichlids

**non native consumers cause more damage to prey populations than do native species

Question 8

Herbivory insect examples?

Answer 8

• introduced insects
• mammalian herbivores on islands

1. Brown Spruce longhorn beetle
   L>10 year lag face
   L. dying red spruce trees
2. Balsam wooly adelgid
   L> no adult forms of trees left
   L> causes a cotton overgrowth preventing PS

Question 9

What happens when a herbivore is introduced to an island system lacking a predator?

Answer 9

• the effect of a herbivore added to an island system lacking predators = the effect of predator removal on plants
• without predation, herbivore density will increase, causing an increased plant extinction

Question 10

Give some examples of herbivores added to an island system.

Answer 10

Goats on Galapagos, Santa Catalina and Raoul Islands

Question 11

Examples of competition?

Answer 11

• interference competition
  L> Zebra mussels effect on native mussels
  L> native mussels in NA burrow and expose a part of their shell to siphon etc where as zebra mussels attach to substrates via threads like the exposed part of the native shell, thus sewing it shut. No native adaptation against that shit

Question 12

Explain the novel weapons hypothesis

Answer 12

• invading plants gain a competitive advantage by possessing allopathic (alter soil chemistry, not harming conspecifics), defensive or antimicrobial chemicals to which native organisms (competitors and herbivores) are not adapted

Question 13

Disease pathogens via invasions.

1. Avian malaria

Answer 13

• Hawaii
• introduced mosquitoes have transmitted avian malaria from introduced Asian songbirds to native Hawaiian honeycreepers
• Asian songbirds facilitated this invasion
• song birds have an immunity to lower the effect of malaria
• song birds benefit from lowered comp by infected honeycreepers via malaria

Question 14

Disease pathogens via invasions.

2. Asian Chestnut blight

Answer 14

• 800 million NA chestnut trees wiped out in 80 years
• fungus transported there via Chinese chestnut trees
• trees couldn’t reach adulthood
• *Asian has immunity

Question 15

Disease pathogens via invasions.

3. Crayfish plague in europe

Answer 15

• carried by NA crayfish introduced to europe
• aided by crayfish farms
• NA crayfish has immunity to the fungus but it jumped shots to the european sp
• *now mostly NA species in europe bc of tis

Question 16

What are the impacts of inter vs intra continental invasions?

Answer 16

• no difference in the probability of causing an impact if the invader is from the continent or another
• boundaries for fish are sub continental
• if you move sp within continent, they will have less of an impact via moving them to a new continent. BUT it doesn’t mean they won’t have any impact in the continent they are moved through

Question 17

Explain the Ecological Distinctiveness Hypothesis

Answer 17

• greatest impacts are caused by invaders that have no ecological equivalent in the invaded system

Question 18

Explain the taxonomic distinctiveness hypothesis

Answer 18

• severe impacts (e.g. declines in resident species) are more likely caused by invaders that add distinct / novel genera to the system bc closely related species are ecologically similar

Question 19

Evidence for the taxonomic distinctiveness hypothesis ?

Answer 19

• 90% of fisheries collapses via invader being a distinct genus
• Problem: no null hypothesis (whats the proportion of invaders likely to be distinct by chance alone )

**high impacts tend to be with novel genus

Question 20

What is the take home message of this section?

Answer 20

1. impact is dependent on evolutionary history and composition of the resident community
2. risk assessment may be informed by phylogenic relationships. Beware the introduction of novel taxa
3. The most severe impacts on biodiversity are caused by novel, uncontrolled consumers introduced to insular habitats ESP generalists