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Biodiversity And Conservation > Local Diversity > Flashcards

Local Diversity Flashcards

1
Q

What is local (alpha) diversity

A

Number of species in a defined area

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2
Q

What is competitive exclusion

A

Most comprise species drive others to extinction

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3
Q

What are regulators of local diversity

A

Processes that enable coexistence

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4
Q

What are the two regulation of local diversity theories

A

Equilibrium theories

Non equilibrium theories

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5
Q

What are equilibrium theories

A

Community diversity is regulated by processes of competition and evolution I.e to attain a steady or stable state

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6
Q

What are non equilibrium theories

A

Community diversity is due to processes that prevent equilibrium being reached I.e interfere with competitive exclusion

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7
Q

When did the equilibrium theories come about

A

1970s

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8
Q

What are equilibrium theories based on

A

Stability
Niche concept
Heterogeneity
Island biogeography

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9
Q

What are niche concepts

A

Focus on one type of narrow part of resources per species. Specialisation enables more species to coexist in a given area.
No overlap as no competition for resource.

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10
Q

What is tight niche packing

A

Resource specialisation. If you can specialise you can pack more species in.

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11
Q

What is broad niches

A

Resource overlaps

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12
Q

What is heterogeneity

A

More diverse habitats have more niches and more niches means more discrete niches and species e.g vertical structure in a Forest - different vertical strata hosts different animals e.g ante and birds

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13
Q

What is the problems with niche-heterogeneity

A 
Mainly zoological (plants have same basic needs I.e water, nutrients and CO2)
Resources and conditions are not partitioned into discrete packages or niches (not natural)
Doesn’t account for most diversity.
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14
Q

Who created the island biogeography theory

A

MacArthur and Wilson

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15
Q

What did Alfred Russel Wallace say in ‘Island Life’

A

It is not too much to say that when we have mastered the difficulties of island life we shall find it comparatively easy to deal with more complex and less clearly defined problems of continental life

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16
Q

What is the central paradigm of island biogeography

A

Discrete, quantifiable, numerous, bounded communities.
Capture species that readily disperse and colonise - bc when an island appears from the sea it has no native species.
Natural laboratories - simplify complexities of natural world.

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17
Q

What is the equation for species diversity

A

F(island area + isolation)

Function of size of island and how isolated it is from the continent.

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18
Q

What is species diversity a balance between forces of

A

Immigration (isolation) and extinction (area)

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19
Q

How does immigration and extinction cause an equilibrium

A

Immigration declines with time as more species become established as new immigrates will be species already present.
Extinction increases with the number of species present.
The part the lines cross is the equilibrium for number of species on an island

20
Q

How does species-area relationship work in the island theory

A

It influences extinction. A later area has more species. When island is late the forces of extinction declines. Areas of island is defining characteristic.

21
Q

Example of a species-area relationship

A

The Galápagos Islands - islands range from 0.2-2249km^2 with 325 plant species

22
Q

What are the two components of the species-area relationship

A

Forces of extinction (death/outward migration). Decline with size:
Greater abundance resources
Greater habitat heterogeneity

23
Q

What does isolation influence

A

Immigration

24
Q

How does isolation influence immigration

A

Forces of immigration greater on near islands and speciation is more important on remote islands. More, less dispersive taxa on closer islands and fewer, more dispersive species on further islands

25
Q

What is the model for the effect of immigration

A

Near islands: lots of species to begin with but rapid drop as less species arrive if they are already there.
Far: the rate of decline of immigration is slower as it takes longer for a species to get there. Rate of reaching the species pool will be slower.

26
Q

What does area influence

A

Extinction as species go extinct more on small islands but less on large islands - doesn’t influence immigration

27
Q

What is the model for extinction

A

Small islands: extinction rises rapidly

Large islands: extinction rises slowly

28
Q

What are the two equilibriums in the island biogeography theory

A

The small/far island equilibrium and the large/near island equilibrium. Intermediate equilibriums for near/small and far/small.

29
Q

What did power (1972) find

A

In the Californian islands area was the factor contributed to most of speciation in plants (0.58) and then it was latitude (0.25) and then unknown variation (0.17).
For birds, the number of play species was most important (0.67) then isolation (0.14) then unknown (0.19) - area strong determinant for plants but not animals.

30
Q

What did Darwin’s finches show

A

Adaptive radiation.
Evolution, natural selection and speciation in the Galapagos.
Fragmentation of land means species living in a forest are basically in island.

31
Q

Summarise the concepts behind the equilibrium theories

A

Niche concepts (specialisation)
Heterogeneity (diverse habitat)
Island biogeography theory (area/extinction and isolation/immigration)

32
Q

What are the non-equilibrium theories

A

Diversity-productivity relationship

Disturbance

33
Q

What is there little evidence of

A

That communities reach equilibrium - only constant in ecology is change

34
Q

What does fluctuating environments lead to

A

Constrain competitive dominants (prevents exclusion)

35
Q

Who created the diversity productivity relationship

A

Grime (1979)

36
Q

What does the diversity productivity relationship state

A

When productivity is slow there’s few species but when it’s high we have species that dominate the community and drive other species to extinction.
Species richness is unimodally related to productivity.
Peak diversity at intermediate productivity (maximum resources). ‘Sweet spot’ for diversity-productivity.

37
Q

What can disturbance be

A

Human but also natural like a tree falling producing a space and prevents opportunities for species.

38
Q

Who created the intermediate disturbance hypothesis

A

Connell (1978)

39
Q

What is the intermediate disturbance hypothesis

A

Low disturbance = competitive exclusion.
Intermediate disturbance = max diversity due prevention competitive exclusion.
High disturbance = low diversity as few species survive.

40
Q

What are the most diverse communities in the intermediate disturbance hypothesis

A

Those subject to a little disturbance like mowed grassland to stop domination but not enough to stop diversity

41
Q

Who created the dynamic equilibrium model

A

Huston (1979)

42
Q

What is the dynamic equilibrium model

A

Highest diversity under conditions where neither disturbance or competitive exclusion dominate - controversial model. Research for exam.

43
Q

Example of empirical test of the dynamic equilibrium model

A

Controlled experiment bc in field there’s too many variables. Can do all the possibilities that you don’t find in the real world. Low grazing plummets productivity.

44
Q

Why is the disturbance model bad

A

Proposing enormous disturbance to natural communities.

Need to be sustainable.

45
Q

Key points

A

Local diversity determined by balance between forces of extinction and immigration.
Forces regulated by range of factors including resource availability, proximity and disturbance.

46
Q

What are the resource conditions

A 
Competition
Predation
Disease
Immigration 
Extinction

Biodiversity And Conservation (10 decks)

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