(chris) 21. Alien plant invasions

Question 1

Not all alien plants become invasive

• Chessnut
• Fennel

(Introduced by Romans to Britain)

Answer 1

Chestnut (friendly alien species, doesn’t expand)

Fennel (grows like a weed, quite invasive)

Question 3

Two most invasive plant species in NZ?

Answer 3

Pine

&

Understorey plant

Question 4

Alien Plant

Answer 4

Many cultivated plants - Strawberrys, Parsnips

Presence due to intentional or accidental introduction as result of human acitivity (exotic plant)

Question 5

Naturalized plants

Answer 5

Eucalyptus spp.,

Strawberrys/Parsnips/Avocados

• Aliens that sustain populations over many life cycles without direct human intervention.
• Most offspring recruited close to parents; do not necessarily invade natural, semi-natural or human-made ecosystem.

Question 6

Invasive

Answer 6

Gorse

Naturalized plants producing reproductive offspring in large numbers, often at large distances from parents plants.

Question 7

Weeds

Answer 7

Manuka on farmland

Plants (not necessariley alien) frowing where they are not wanted, and which have detectable economic or environmental effects.

(Manuka originally seen as weed)
-worth carbon credits

-mankes manuka honey $$

Question 8

Envrionmental weeds

Answer 8

Privet

Alien plants that invade natural vegetation

Question 9

Transformers

Answer 9

Pinus contorta

Subset of invasive plants that significantly change the character, condition, form or nature of ecosystems.

Question 11

Why care about plant invasions?

Answer 11

• Displacement of native species
• Displace habitat of ground-nesting birds (dotterels,stilts,terns)
• Also allow predators to ambush birds as they block visual line of sight.

Question 12

In Australian savanas, invasive grasses increase..

Answer 12

fire intensity.

Question 13

Alteration of ecosystem services..

Answer 13

Disruption of toursim

(lamenting the spread of wild conifers)

Question 14

What determines invasion “success” ?

Answer 14

• Climatic suitability
• Residence time
• Propagule pressure
• Dispersal traits
• Reproductive traits

Question 15

Familiarise

Dispersal - Get to New Zealand

Physiological - Deal with environment factors

Biotic - Deal with competition (herbivores/parasites)

Question 16

Do plant traits explain invasion?

(weedy plants)

Answer 16

Weedy traits:

• fast growing
• associated with disturbed habitats

Plants reported as invasive are consistantly faster-growing than non-invasive congeners.

Short-term bias in data. because invasions by slow-growing shade tolerent species may take longer to make an impact?

YES…BUT!

But invasive plant in NA found to grow faster than native trees of similar shade tolerance, how? Because it has escaped it natural predators perhaps from home environment.

Question 17

Escape from specialist enemies in new environment means the exotic plant…

Answer 17

..is subject to less herbivore pressure than its new neighbours, giving it a competitive advantage,

Question 18

Familiarise

Answer 18

Question 19

Question 20

Weevils introduced to control gorse.

(weevils eat seeds)

Answer 20

Lifecycles do not line up

Question 21

Introduced to N.A

Answer 21

Question 23

Answer 23