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community ecology > final > Flashcards

final Flashcards

1
Q

what is Hubbell’s Unified Theory of Biodiversity and Biogeography

A

that all species are functionally equivalent and have an equal chance of colonizing an open space

niches are functionally equivalent

offspring and immigrants all compete for open spaces

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2
Q

what is point mutation (v)

A

per capita speciation rate

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3
Q

how does the absence and presence of niche differences affect a species growth rate

A

when niche differences are present: growth rate declines with increased abundance

when absent: species abundance has no effect on growth rate

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4
Q

what is a metacommunity

A

set of communities linked by dispersal pf one or more of their constituent species

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5
Q

what is a regional species pool

A

set of species found in a region

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6
Q

what is a local species pool

A

sunset of regional pool found in local community

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7
Q

what are the results of neutral theory in a community

A

dominance increases are rarer species goes extinct

species diversity in a local community is maintained by immigration

regionally abundant species tend to be locally abundant

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8
Q

what is island biogeography theory

A

how big an island (or isolated part of mainland) and how far away it is determines the species richness there

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9
Q

what is facilitation (positive interactions)

A

encounters between organisms that benefit at least one of the individuals and harms neither

can be direct or indirect

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10
Q

what is mutualism

A

facilitative interaction where both species benefit

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11
Q

how does facilitation change the view of the niche

A

makes realized niche bigger than fundamental niche

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12
Q

when are positive interactions most common

A

under harsh environmental conditions

or extreme stress

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13
Q

what is the stress gradient hypothesis

A

about relative importance of competitive or facilitative interactions changes along a gradient of environmental harshness

competitive interactions should dominate in benign environments

facilitative interactions should become more important in stressful environments

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14
Q

how does relative neighbour effect change with changing environmental effects

A

increased environmental severity: positive (facilitation)

decreased environmental severity : negative (competitive)

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15
Q

what is the Hairston smith slobidkin hypothesis (HSS)

A

top down approach

carnivores, having no predators, are limited by food

herbivores are held below carrying capacity by by predators

plants aren’t controlled by herbivores and are abundant

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16
Q

what did Oksanen propose about atrophic levels

A

biomass at each trophic level should change as potential productivity increases

as potential primary productivity increases the number of possible trophic levels increases

biomass at each trophic level changed depending on number of trophic levels

bottom up approach

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17
Q

what does oksanen predict in a 3 trophic level community

A

As potential primary productivity increases :

producer biomass increase

herbivore biomass remains constant

carnivore biomass increases

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18
Q

what is a trophic cascade

A

indirect/direct effects a predator has on the density or behaviour of species in lower trophic levels

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19
Q

how do cascades differ in terrestrial and aquatic systems

A

weak in terrestrial

variable in aquatic systems

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20
Q

when do cascades only occur

A
  • cascades/top down effects occur only when :
  • direct effects are strong
  • producer densities are not limited from bottom up
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21
Q

what make strength of predator-prey interactions vary

A

predator functional response

body size

energetic requirements

herbivore vulnerability

primary producer palatability

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22
Q

what do food chains represent

A

transfer of energy between trophic levels in a community

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23
Q

what is a trophic level

A

identifies a species position in the food chain

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24
Q

what trophic level is the base of the food chain

A

primary producers

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25
Q

how can food chains be described

A

number of trophic levels

level of connectance

link density

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26
Q

what is connectance

A

fraction of all possible links that are realized

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27
Q

what is link density

A

mean distance between all nodes in a web

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28
Q

how many trophic levels is rare in a community

when does it occur

A

3 (producer, herbivore, carnivore)

occurs when productivity is low (ex: dessert, Arctic)

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29
Q

how many trophic levels is common

A

4, 5, 6

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30
Q

what are the hypothesis of food chain length

A
  • energy limitation / productivity hypothesis : since energy is lost at each level, length is limited by available energy
  • ecosystem site hypothesis: larger ecosystems can support more species, which results in more links, leading to longer food chains
  • productive space hypothesis : productivity and size work together to determine length
  • dynamic stability / disturbance hypothesis: since longer chains are less stable, food chain length will be an outcome of what is feasible and and the frequency of disturbance
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31
Q

what is the 10% law

A

only 10% of energy is transferred to next trophic level

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32
Q

what determines the amount of energy reaching each trophic level

A

NPP and efficiencies

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33
Q

who are most efficient at assimilation

least efficient

A

animals are most effect

plants and bacteria mid

detritus are least

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34
Q

why do carnivores have higher assimilation efficiency than herbivores

A

food easier to digest and higher in energy

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35
Q

what direction do arrows in web point

A

towards consumer

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36
Q

what is resistance

A

measure of the ability of a community to avoid change

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37
Q

what is ecological resilience

A

how far a community can be disturbed and return to its original state

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38
Q

what is engineering resilience

A

time it takes a community to recover

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39
Q

what is a community / Jacobean matrix

A

matrix describing interaction strengths in a food web

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40
Q

what are the beliefs of relationship between diversity/complexity and stability

A

diversity = stability

  • simple communities show greater fluctuations in species abundance and are more vulnerable to invasion (Elton)
  • more complex communities buffered from species loss (MacArthur)
  • complexity, weak interactions, and type 3 (adaptive foraging behaviour) stabilizes food-webs (McCann)

diversity = less stable

  • communities with more species and links are less stable (May)
  • increased diversity, trophic levels and connectance reduced stability (Primmer and Lawton)
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41
Q

how can diversity both benefit and harm stability

A

depends how you look at stability

if looking at ecosystem level: since if species vary in their response to environmental fluctuations, so increased abundance of one species can compensate for decreased abundance of another

If you are looking at the species level: since there is a max number of individuals that can live in a community, the more species richness there is the less of each species there can be. The smaller population size can then make that species more likely to go extinct

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42
Q

what did primm and lawton predict about resilience and already stable food webs

A

adding trophic levels decreased resilience

increasing connectance increased resilience

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43
Q

what is a bipartite network

A

illustrate connections between 2 trophic levels or between mutualists

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44
Q

what is persistence

A

proportion of initial species that remain in the system

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45
Q

what is nestedness

A

degree to which generalists associate with all species

specialists associated with generalists

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46
Q

what is modularity

A

the degree to which species associate with species within their group more than in other groups

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47
Q

how do trophic networks differ from modular networks

A

trophic networks are less connected and more modular

mutualistic networks are more nested

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48
Q

how does modularity effect persistence and resilience in mutualistic networks

A

both reduce

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49
Q

how does nestedness effect persistence in trophic networks

A

reduces persistence

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50
Q

how does connectance effect persistence and resilience in both mutualistic and trophic networks

A

mutualistic: promotes both
trophic: reduces both

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51
Q

why doesn’t productivity have an alternating effects on the biomass of adjacent trophic levels

A

trophic levels aren’t homogenous

a shift in potential productivity can shift from better resource competitor to more predator-tolerant species

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52
Q

what is the green channel

A

live consumer system

53
Q

what is the brown system

A

decomposer or detrital system

54
Q

what channel is more productive

A

green channel is faster (more productive)

brown channel is slower (lower biomass turnover)

55
Q

what channel is more species rich, with more links, and weaker interactions

A

brown

56
Q

what is ecological subsidy

A

the flux of organic matter/nutrients from a donor population to a recipient one

57
Q

what is an ecotone

A

transition area between biomes and ecosystems

58
Q

what is allochthonous

A

originating from outside the community

59
Q

what is an autochthonous

A

originating in community where found

60
Q

what can using resources from multiple ecosystems do

A

stabilize rapidly changing environments

61
Q

what is the prediction in looped food webs

A

energy flow through brown channel increases abundance of top predator

top predator prefers herbivores prey over detrivore prey

detrivores increase in abundance as detritus builds up

62
Q

why are looped webs linked at top and bottom

A

`linked on top by generalist predator that eats both herbivores and detrivores

bottom: since detritus is made of decaying organic matter

63
Q

what causes the predicted inverse response of detrivores and herbivores to nutrient enrichment

A

since energy flow through detritus pathway is expected to increase abundance of top predator who prefers to eat herbivores

64
Q

what is expected about diet of predators in response to nutrient enrichment (brown and green model) why

A

larger portion of diet comes from brown channel

as predators increase in abundance there is more competition for their preferred prey (green)

65
Q

what is apparent competition

A

form of competition where species/individuals indirectly compete since both are prey to same predator

66
Q

what link ecosystems

A

allochthonous inputs

67
Q

what does species diversity in slow channels lead to

A

skewed distributions of interaction strengths that help stabilize entire ecosystems

68
Q

what are responses in primary productivity the result of

A

multi channel control

69
Q

what are ecosystem functions

A

the benefits people obtain from the ecosystem

70
Q

what are the categories of ecosystem services

A

provisioning services: food, water, raw materials

cultural services: non-material services that provide spiritual, aesthetic, or recreational opportunities

regulatory services: control climate, and buffer against disasters, purify water

supporting services: support other services such as nutrient cycling, soil formation, primary productivity

71
Q

what model helps us understand how many species we need

A

rivet redundancy

72
Q

how does diversity effect ecosystem function

A

niche complementarity: species use different resources, so communities with more resources use more

facilitation: some species alleviate environmental conditions for other species

sampling/selection effect: having more species increases likelihood of having an effective one

73
Q

what can positively effect the strength of complementarity effects between diversity and function

A

time and habitat heterogeneity

74
Q

are sampling effects more or less important in aquatic environments

A

less

75
Q

what is the biotic resistance hypothesis

A

ecosystems with high biodiversity are more resistant against immigration

76
Q

what are portfolio effects

A

describes the degree to which diversity reduces variability in ecosystem service

more diverse portfolio fares better when conditions are variable

77
Q

when can diversity stabilize temporal diversity

A

when there is variation in response to environmental conditions

78
Q

what is a regime shift

A

a change from one community to another

79
Q

what is a tipping point

A

critical threshold at which a system undergoes a regime shift

80
Q

when are abrupt changes easily reversible

when are they hard

A

easy: if communities continue along a single path
hard: communities differ in their response to environmental conditions

81
Q

what creates a hysteresis loop

A

delayed response to forward and backward changes in environmental conditions

82
Q

when are alternative stable states possible

A

in a hysterisis loop

83
Q

what must be shown to demonstrate alternative stable states

A
  • communities must have an equilibrium support
  • move to a second equilibrium point after a disturbance
  • remain in alternative state after disturbance is gone
  • abiotic environment isn’t altered
84
Q

what is a disturbance

A

a relatively discrete event in time that causes abrupt change in ecosystem

85
Q

how can a disturbance be described

A

size, time, severity, dispersion

86
Q

what is succession

A

pattern of change expected in a community over time after a disturbance

87
Q

what is primary succession

A

sequence of change after a catastrophic event

88
Q

what is secondary succession

A

sequence of change after a smaller disturbance

89
Q

what is chronosequence

A

series of current communities of known age that reflect succession

90
Q

what is a sere

A

unit of succession

91
Q

what is a seral stage

A

distinct communities within a sere

92
Q

what is a pioneer community

A

initial seral stage

93
Q

what is a climax community

A

final seral stage

94
Q

what were the early views of succession

A

clements: saw succession as a predictable and orderly progression from bare state to climax community

Gleason: saw succession as a continuous process with no end point

95
Q

what does chronosequence suggest about predictability of succession

A

predictable and linear

but experiements are on small scale

96
Q

why are climax states rare

A

succession is slow

further disturbances reset it

97
Q

what is the relay floristic model

A

deterministic changes from pioneer to climax community

groups of species successively appear and disappear from site

will slowly make conditions less favourable for themselves, but more suitable for another species

98
Q

what in the initial floristic model

A

all species are present in the begining, and species assume dominance over time

99
Q

what are camel and slayter’s 3 mechanisms for succession

A

facilitation : early successional species modify environment to make it more conducive for more species

tolerance: any species that arrives can establish, but r-selected species are eventually outcompeted by k-select species
inhibition: early species inhibit and slow down establishment of later species, slowing succession

100
Q

what is a r-select species

A

small investment in offspring, but many

less competitive, but need less resources to reproduce

high mortality rate

101
Q

what is an k-select species

A

heavy investment in each offering, few offspring

more competitive , live longer

102
Q

what does the competitive stress ruderal triangular model (CSR) predict

A

disturbance creates empty space that initially favours ruderal species
fast growth/dispersal and early rates of maturity

mid seral stage has less empty space and favours more competitive species

late seral stage has fewer resources and favours stress tolerant species

103
Q

what is the life history strategy model of succession

A

emphasized adaptations to disturbance (promote dispersal) and adaptations to competition (growth rate)

similar to CSR but less abstract

104
Q

what is the resource ratio hypothesis for plant succession

A

alternative to CSR

based on ability of plants to extract resources

succession was considered to be outcome of colonization - competition trade off

105
Q

what does seed arrival have a big role in

A

primary succession

106
Q

what does seed bank have a large role in

A

secondary succession

107
Q

what environments are chance events and facilitation most important

A

severe environments

108
Q

what environment is competition more important

A

favourable environments

109
Q

when in succession is fast growth rate most important

A

early on

110
Q

when in succession is longevity important

A

later stages

111
Q

when is mammalian herbivory more important in succession

A

early

112
Q

when in succession is insect herbivory most important

A

later in succession

113
Q

what is a regional species pool

A

all species that could possibly colonize a community

114
Q

what is a local species pool

A

species present in a local community

115
Q

what are assembly rules

A

rules that specify why only a limited subset of species of the regional pool is in the local pool

116
Q

what is a guild

A

a group of species that exploit the same class of resources in a similar way

117
Q

what are diamonds assembly rules

A

1- forbidden species combinations

2- resource availability can alter which species can coexist

118
Q

what is hutchinsonian ratios

A

there are limits to similarity

reduced niche overlap reduces competition and allows species to coexist

119
Q

what did McCloskey believe about observed and imaginary communities

A

when you have an open system it is untstable so you wouldn’t observe it in nature (imaginary), since another species would come in and filled the gap, thus stabilizing the community making into an observed community which would use more resources (more individuals )

120
Q

what is Fox’s favoured states model

A

favoured: if resources to different guilds are approximately equal if all guilds have equal representation
unflavoured: if some guilds are over represented

121
Q

what are the community assembly filters

A

dispersal: may limit which species reach a local community

environmental effects: determine what traits are adaptive

biotic filters: such as competition, predation, disease, etc…

122
Q

when are chance events most important in community assembly

A

most important when the species pool is large, dispersal is low, primary productivity is high, and disturbance is low

123
Q

what is species sorting

A

emphasizes differences in species ability to utilize different patches (species differ in fitness in different environment)

dispersal has no effect on outcome of species interactions

124
Q

what are mass effects

A

considers that species differ in niches, but emphasizes role of dispersal

dispersal effects are assumed to be high and with significant effects on population dynamics and species diversity

125
Q

how does amount of dispersal affect diversities

A
  • alpha : initially increases as less competitive species are saved as less fit (to particular environment) immigrate
  • beta: declines with increased dispersal since communities are becoming more similar
126
Q

what do the overall theories suggest about recovery

A
  • degraded community may be stable and resist recovery
  • natural processes may not lead to recovery
  • if the abiotic environment is completely restored, the restored community may not be a complete carbon copy of original
127
Q

how does predator diversity with omnivory and intraguild predation effect strength of cascade

A

predator diversity with omnivory and intraguild predation reduces strength of cascade

128
Q

how does predation on mutualists affect the effects of predators on plants via herbivores

A

predation on mutualists can counter positive indirect effects of predators on plants via herbivores

community ecology (2 decks)

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