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Population Ecology > Week 4-5 > Flashcards

Week 4-5 Flashcards

1
Q

What is a metapopulation

A

Many populations of a single species in a region linked by immigrations and emigrations

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2
Q

What is the model for geometric growth for an open population

A

Nt+1= Nt+ B – D + I - E

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3
Q

What are the dynamics of a metapopulation determined by

A

by the
rate of colonization of empty patches and extinction of
individual subpopulations

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4
Q

What are the 3 stages of dispersal

A

emmigration, transfer and immigration

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5
Q

Define dispersal

A

The movement of individuals away from others

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6
Q

Define migration

A

the mass directional movement of large numbers of individuals of a species from one location to another

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7
Q

What is natal dispersal

A

the movement between the location where individuals are born and where it reproduces

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8
Q

What is breeding dispersal

A

movement between two successive breeding areas

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9
Q

What are the 4 dispersal mechanisms

A

passive dispersal
passive dispersal by mutualistic agent
active dispersal
clonal dispersal

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10
Q

What is passive dispersal

A

Non-exploratory, destination is a matter of chance, like dandelion seeds

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11
Q

What is passive dispersal by a mutualistic agent:

A

animals eating fruit and defecating the seed away from the original tree

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12
Q

what is active dispersal

A

dispersal controlled by the individual

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13
Q

What is a clonal dispersal

A

common on modular organisms, an individual branch spreads its parts around as it grows

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14
Q

What is random disperson

A

when an organism has the tendency to avoid other organisms or when organisms

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15
Q

What is aggregated dispersion

A

when individuals are attracted to parts of the

environment or by other individuals

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16
Q

Types of seed dispersal

A
  • gravity,
  • wind,
  • ballistic,
  • water and
  • by animals
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17
Q

What is density dependent dispersal

A

Dispersal depends on local population size, availability of resources, habitat quality and habitat size

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18
Q

Example of density dependent dispersal

A

Large aphid populations have a lower growth rate than small ones as more aphids are dispersing

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19
Q

Example of inverse density dependent dispersal

A

Grey-tailed voles were found to disperse less when part of a large population than at as small due to males wanting to overlap several female territories

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20
Q

What species use density independent dispersal

A

All species that use
passive dispersal by wind, gravity or currents (plants,
spiders, some insects, fish)

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21
Q

What are the 3 main evolutionary consequences of dispersal

A

Inbreeding avoidance
Competition avoidance
Philopatry

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22
Q

Why is inbreeding avoidance important

A

Because when close related individuals breed they are likely to suffer from inbreeding depression in fitness -favours dispersal

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23
Q

What is philopatry

A

tendency of an organism to stay in or habitually return to a particular area`

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24
Q

Why is outbreeding depression a force against dispersal

A

long distance dispersal may bring together genotypes that are adapted to different environments and the resulting offspring may not be adapted to either environment

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25
Q

Example of a highly philopatric bird

A

lesser kestrel are highly philopatric, returning to very specific wintering sites

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26
Q

What are the general sex-related differences in dispersal across taxa

A

Insect males disperse more than,females (males look for females in large areas, while females look for host plants to lay eggs)
– Birds, usually the females
disperse (males compete for
territories and females select
the best territory/male)
– Mammals, usually the males disperse (males compete with other males for mates, so look for the places with most
females)

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27
Q

What is a source of variation in dispersal within a population

A

Age differences provide a lot of variation.
A lot of plants,mammals and birds use natal dispersal
Marine invertebrates the larval stage ismresponsible for dispersal
Insects, the adult disperses the eggs, the larva
move very little

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28
Q

Example when dispersal ability is a trade off

A

Glanville fritillary that the lifetime egg production is 4% smaller on average in the more dispersive butterflies due a trade off between high metabolic performance and reduced maximal life span.

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29
Q

What is population synchrony

A

The correlation of temporal fluctuations in population dynamics between different
localities

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30
Q

What factors promote synchrony

A

weather
predation
dispersal

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31
Q

Advantages of synchrony

A

Lower predation risk for each individual (linked to
aggregation and to the advantages of aggregation, e.g.
cicadas)
– Easier to find mates

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32
Q

Disadvantages of synchrony

A

In the case of disease it may wipe out all populations that are synchronised and connected by dispersal
In case of extreme weather event
Competition for resources

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33
Q

What is the population equation that that takes into account dispersal

A

Nt+1= Nt+ B – D + I - E

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34
Q

Why is dispersal important

A

subtract and add individuals to a population
alter the outcome of species interactions
provide crucial genetic variability
rescue populations from extinction

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35
Q

What dispersal studies do not include tagging

A

Detection of range expansion (in the case of
the butterflies it gives dispersal per generation)
Video cameras
Detection of animal tracks and signs

36
Q

Dispersal studies with artificial markings

A 
Mark-recapture
Tracking paths (direct observation)
Telemetry (Satellite, geolocators, etc)
Vertical looking radar (VLR)
Genetic markers
37
Q

Why do we need more dispersal studies

A

The dispersal curves of many species are not
known
the tail of the distribution of
dispersal of many species is not known
For both insects and trees expanding their range after the last glaciation, long distance dispersal is essential to produce the patterns of distribution we see today

38
Q

What is the relationship between dispersal and global environmental change

A

Thomas et al 2004 created a model which estimated percentage of extinctions depending on different climate projections. They found that in the worse case scenario, with no dispersal, 58% species will go extinct

39
Q

What is the simple diffusion gradient

A

distance moved = Dn*(the square root of log e * R0)
D = average dispersal distance
n = number of generations
R0 = reproductive rate per generation

40
Q

In terms of dispersal, what does modern DNA allow us to do

A

Modern DNA technology allows the identification of migration routes

41
Q

When does a hybrid zone occur

A

Hybrid zones result from two

divergent genomes that have expanded from two different glacial refugia

42
Q

What similarities did Hewitt find in dispersal pattern after the last glacier

A

(a) grasshopper, crested newt and alder
(b) hedgehog, oaks and beech
(c) bear shrews and water voles

43
Q

What is a population

A

a discrete group of individuals living in an area with little immigration of emigration, generally the same gene pool

44
Q

What are characteristics of a metapopulation

A

consists of many smaller local populations
small movements between sub-populations
can allow individuals to persist in fragments

45
Q

What characteristics of metapopulations did Levins 1970 describe

A

Each local population has a substantial probability of extinction
Long term persistence can only occur at the regional or meta population level

46
Q

What is a source population

A

A population in a good habitat that exports migrants

47
Q

What is a sink population

A

A population in a poor quality habitat that receives migrants

48
Q

Why do sink populations need migrants

A

Sinks have low breeding success or high mortality rate so their population growth rate is less than 1, so without migrants, sinks would become locally extinct

49
Q

What does lambda represent

A

intrinsic rate of population growth

50
Q

What is Levins metapopulation model equation and what does it show

A

The rate of change in the fraction of occupied habitat (patches, p)
dp/dt = mp(1 − p) − μp
μ is the rate of local extinction of patches
m is the rate of recolonization of empty patches

51
Q

In Levins model, what is required to keep meta populations at a stable equilibrium

A

The intrinsic rate of recolonisation exceeds the intrinsic rate of extinction

52
Q

Why is it important to look at trends in the metapopulation and not just local

A

Local populations can be very unstable and be susceptible to local extinction, and thus we need to look at metapopulations to understand long term persistence

53
Q

Reasons why organisms would show philopatric behaviour

A

advantages of inhabiting a familiar environment;
individuals may cooperate with or tolerate related individuals in the natal habitat that share a high
proportion of their genes
Dispersers could meet a social fence from aggressive unrelated individuals

54
Q

What are 3 necessary features of metapopulations

A

that individual subpopulations have a realistic chance of experiencing both extinction
and recolonization
The dynamics of the various subpopulations should be
largely independent, i.e. not synchronous

55
Q

Why, for the metapopulation to persist, can’t the sub populations be dependent

A

little hope of stability if when one subpopulation went extinct they all did.

56
Q

Does patchiness = metapopulations

A

No, for three reasons
Population may be patchily distributed but so much dispersal that the patches aren’t independent or
patches may be so isolated from one another that dispersal between them is negligible
all patches may simply
have a negligible chance of extinction, at least on observable
timescales. (so sig degree of extinction or recolonization.)

57
Q

Why are corridors important

A

corridors facilitate exchange rates of organisms between otherwise isolated patches

58
Q

Why are corridors important for pollinators

A

important for maintaining genetically viable populations of the plants that they pollinate

59
Q

What is the Traditional Corridor Hypothesis

A

corridors function as movement conduits, channelling dispersing organisms between connected habitat patches

60
Q

List of benefits to corridors

A

increase immigration and emigration, stem inbreeding
depression, lower extinction rates, lessen demographic
stochasticity, and generate higher population
densities

61
Q

What is the Drift Fence Hypothesis

A

at corridors function as drift fences, ‘‘intercepting’’ organisms as they disperse through matrix habitat and redirecting them into habitat patches attached to the corridor

62
Q

Evidence against drift fence hyopthesis

A

Townsend and Levy 2005 compared pollen flow to plots with corridor ‘wings’ and those without. No sig diff

63
Q

Who created the millennium goals

A

Convention for biological diversity

64
Q

What are the root causes of biodiversity loss the 2020 conservation targets address

A

Habitat destruction and fragmentation (e.g. stop deforestation)
Climate change (e.g. agreement on reduced emissions and carbon capture and storage)
Over-exploitation (e.g. sustainable fisheries)
Invasive species (e.g. control invasive species to prevent extinction of endemic species)
Pollution (e.g. significant decrease pollution levels

65
Q

In 2018, how much of the world is protected

A

3.6% MPA Sala et al 2018

66
Q

Why do scientists disagree on how much of the land is protected

A

Because protected areas still under intense human pressure and sala et al 2018argue that only strongly or fully protected areas actually succeed in protecting biodiversity

67
Q

Example of when a PA has not been effective

A

Kruger to the Canyons Biosphere Reserve has experienced deforestation

68
Q

What determines a species ability to shift range

A 
Degree of habitat
fragmentation
Species dispersal
ability
Presence of
competitors, parasites
and predators
69
Q

Why are static protected areas still effective during changing climates

A

They are the first to be colonised by range expanding species
They help retain conracting species in the landscape

70
Q

How much has the global climate warmed during the 20th century

A

0.8 C

71
Q

Who recommended the use of ecological networks and corridors

A

Hopkins et al 2007

72
Q

What did hopkins et al 2007 recommend

A

ecological networks to improve connectivity between habitat patches by habitat expansion, and establishing physical linkages such as corridors and habitat “stepping stones”, and improving the permeability of the matrix to species movement.

73
Q

How many butterfly species have decline in Britain since 1970

A

34/46

74
Q

How does range shift differ between generalist and specialist butterflies

A

Specilaist sedentary butterflies = range cintracting

Mobile generalists = range expanding

75
Q

What are the 3 purposes of corriodors

A
  1. routes and habitats for organisms responding to climate change
  2. Allow movement of
    individuals, some species
    move using major pathways
  3. Increasing the movement of individuals among otherwise isolated populations
    – Rescue from stochastic local
    extinction
    – Maintain genetic diversity
76
Q

What is connectivity

A

measure of how a landscape facilitates or impedes the movement of individuals between habitat patches

77
Q

What are the two ways connectivity can be described

A

functional and structural

78
Q

What is structural connectivity

A

structural connectivity of the landscape is the degree to which habitat patches are physically linked

79
Q

What is functional connectivity

A

depends on a species dispersal ability
the size and spatial arrangement of habitat patches
the nature
of land cover and land use in the intervening matrix.
ie what may be functionally connected for one species wont be for another

80
Q

In terms of edge effects, what is a disadvantage to corridors

A

Have a high edge effects
May at as a sink attracting species into high edge proportion areas which may increase their mortality and predation risk (evidence needed)
For edge averse species,
corridor width needs to be
such that some portion of the corridor represents core
habitat

81
Q

Described Haddad (1999) evidence that corridors work

A

He studied the variegated fritillary and found that their movement between adjacent patches increased with corridors

82
Q

Why may corridors increase population size of isolated populations

A

They provide a rescue effect against stochastic extinction

83
Q

Why might their be higher densities in connected patches than unconnected (evidence)

A

Greater effective area caused by corridor e.g bird biodivesity in small connected vs small isolated (schmiegelow et al 1997)

84
Q

What is the benefit of a wrap shaped corridor rather than linear

A

Buffering core populations may be more efficient than increasing connectivity among numerous vulnerable populations aiding in the rescue effect

85
Q

Disadvantages of corridors, other than edge effect

A

can increase incidence of biotically dispersed parasites
may act as a sink when high quality patches are nearby
increase invasion by exotic species

86
Q

Why are large scale and continental scale corridors important

A

To support population connectivity, gene flow, range responses to climate change, or dispersal / home range movements of large-area species

Population Ecology (5 decks)

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