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Ecology of Species Invasions > Lecture 5: Population dynamics of invader > Flashcards

Lecture 5: Population dynamics of invader Flashcards

1
Q

Explain the intentional release of the European Starling.

A
  • released birds in central park to have birds from Shakespeare plays.
  • all birds we see now are pretty much descendants from these
  • 60 released in NYC 1880
  • 40 more in 1891
  • Present pop in NA = 200 million
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2
Q

Explain the intentional release of the European house sparrow.

A
  • Initially 16 released in NYC 1851
  • 100 more in 1852
  • *initial 16 did not survive but the 100 did establish
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3
Q

Are all planned introductions successful?

A
  • no

- most fail to become established

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4
Q

The probability of invasion increases with what?

A
  • the number of attempted introductions and with the total number of colonizers
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5
Q

Do small or large populations have a higher extinction risk? Why?

A
  • small
    -bc of demographic stochasticity (i.e. bad luck)
  • minor glitches in reproduction or survival can wipe out a small population
    Gamblers Ruin
  • ## if in small numbers, you do not have the numbers to buffer against fluctuations in the environment that are unfavourable etc – worse if you don’t have meta populations bc no rescue effect.
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6
Q

Give the reasons of why small populations have higher extinction risks.

A
  • demographic stochasticity
    L> glitches in reproduction or survival can wipe out a small population
  • small gene pool
    L. insufficient genetic variability to adapt to environmental changes
  • population is spread too thinly
    L> mate location becomes difficult
    L> can be wiped out easily bc all in one close location
  • vulnerable to small scale environmental stresses
    L> e.g. fire, storms, predation, disease

*** small populations need to be able to reproduce from small numbers to escape these fast to successfully establish

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7
Q

What is propagule pressure and what are the two types when involving only a single species .

A
  • aka inoculation pressure/ introduction effort
  • ** the quantity / rate of propagules (life stages) delivered to a site
    1. Propagule size
    2. Propagule number
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8
Q

What is propagule size?

A
  • number of individuals in a given introduction event
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9
Q

What is propagule number?

A
  • the number of introduction events
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10
Q

What are the two classes of propagule pressure?

A
  1. must introductions of propagules of a single species (propagule size and propagule number)
  2. multiple introduced species aka colonization pressure
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11
Q

Explain the relationship btwn propagule size and establishment for mammals introduced to Australia

A
  • highlights when a large number are initially introduced there is a better chance of establishment
  • also demonstrates you do not get a successful establishment on first introduction
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12
Q

Explain the proportional success of introducing different numbers of birds of a species in New Zealand

A
  • if there are more than 50, establishment is likely
  • there is a point where once you pass a certain threshold, it no longer matters how many you add, more so if they are aded in the right place
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13
Q

Explain the relationship of the number of introduced and established aquarium fish in Can and US as a function of popularity

A
  • dumping depends on what ppl are buying
  • some are more pop than others
  • if something is popular there will be more of them in stores and diversity of stores to provide public demand
  • how popular the fish is, is a proxy of propagule pressure. More popular = more being sold = more in tanks that eventually might be dumped
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14
Q

Explain the relationship btwn ship vectored invasions and shipping activity in the great lakes

A
  • the more water being dumped out, the more propagules being pumped out THEREFORE a proxy of PP
  • water release is a proxy of shipping activity too
  • as shipping activity increases so does the number of species invasions
  • could also reflect our increasingly better detection methods
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15
Q

Explain the spread of fire ants around an African oilfield through movement of oil rig platforms

A
  • vector activity can be a proxy for propagule pressure
  • oil rigs carried mud and insect around, invasive ants are an example
  • small number of oil rig visits, small prob of establishment but AS it increases, prob of establishment increases
  • eventually reaches an asymptote
  • point is that it doesn’t go on forever
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16
Q

Explain the relationship between species richness and number of species added as seed

A
  • number of seeds in plot and those coming out
  • number of sp that become established are a direct function of the number of seeds added
  • limited by recruitment and dispersal = for seeds
  • colonization pressure is occurring: species numbers not number of individuals of one sp
  • sp richness increasing with number of sp added as seeds increases
17
Q

Explain the success of introduced salmonid fishes vs propagule supply

A
  • both introduction attempts and number of individuals matters
  • add a lot of fish and repeat
  • by introducing many over diff time periods, you are opening windows of opportunity
18
Q

Are there ever exceptions to the trend with propagule pressure?

A
  • yes
  • very small risk
  • sometimes small numbers can lead to an invasion
19
Q

Describe examples of when small numbers of sp can lead to invasions.

A
  • Mitred parakeets colonized Maui from a single pair released by a resident
  • muskrats invaded europe when five escaped from a fur farm
  • a single pair of sheep released in Kerguelen islands resulted in a population as large as 700 in 30 years
  • ** Noah Fallacy : assuming all you need is one breeding pair
20
Q

What are the three hypothetical relationships between invasion success and propagule supply.

A
  1. Threshold effect
    L> after while adding more individuals isn’t enough and will asymptote
  2. Continous marginal benefit
    L> direct linear relationship rarely happens bc usually other environmental factors will influence this
    L>the more you add, the further the benefit and this will continue over time (don’t expect with asexual reproducing orgs)
  3. Logistic
    L> s shape
    L> threshold where before you get little if anything, anything above it increases to a point. This threshold will vary with each context even for the same sp.
21
Q

Explain the interactive effects of propagule size and number of experimental Daphnia populations.

A
  • basically BOTH matter

- as propagule size and number increase, so does avg pop size

22
Q

Explain why survivorship of propagules in ballast tanks decline over time

A
  • propagule quality decreases via enviormenta; pressure bc of what is delivering them
  • phytoplankton and zooplankton decline as the voyage goes longer
  • if the voyage is shorter, the number of individuals will be more that are released
  • physical condition will also be different
  • organismal density decreased overtime in ballast water
23
Q

Explain the relationship with species richness and time in ballast water

A
  • the pathway chosen will determine the quality or nature of propagule pressure
  • if ballast water has been there long the quality and quantity of individuals will be less
  • this is more of an issue if quality of water is not replenished over time
  • what happens to the vector determines the propagule pressure
  • number of species decreases as the days increase since the last taking of ballast water
24
Q

Explain Lonsdale’s model

A

E= I x S

E= number of exotic species in a region

I= number of species introduced (propagule pressure)

S= survival rate of introduced species (biological traits of the invader; habitat quality)

  • colonization pressure = number of species introduced which depends on vectors
  • survival rate depends on the relationship btwn the invader and the environment
  • habitat quality it is also important upon introduction, which varies over time
    • basic idea is that propagule pressure and environment matter BOTH of which vary over time
  • it explains why the same sp can fail many times and invade in another situation
  • *** SO even if it is introduced to a suitable habitat it does not sure establishment

Ecology of Species Invasions (22 decks)

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