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Ecological communities. Community. Guild. Assembly. A community is a local assembly of species that potentially interact. Generally these species are on the same trophic level . A community of species with similar niches is called an ecological guild. Counter examples - PowerPoint PPT Presentation
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Ecological communities
A community is a local assembly of species that potentially interact.
Generally these species are on the same trophic level.
A community of species with similar niches is called an ecological guild
Examples of ecological communities
Insect eating birds in a forest.Fish in a pond.Butterflies on a meadow.
Counter examples
Birds in a forest form an assemblyAphids and Ladybeetles are on different trophic levels.Fish in an archipelago form meta-communities.
Assembly
CommunityGuild
Examples of communities
Plant visitors and pollinators Nepenthes pitcher plants
Deep sea bacterial communities
Calcareous grassland
Assemblages but not communities
Mutual effects of species interections:
Direct effects refer to the impact of the presence (or change in abundance) of species A on species B in a two-species interaction.Indirect effects refer to the impact of the presence (or change in abundance) of species A on species C via an intermediary species (A --> B --> C).Cascading effects are those which extend across three or more trophic levels, and can be top-down (predator --> herbivore --> plant) or (plant --> herbivore --> predator).Keystone species are those which produce strong indirect effects.
The starfish Pisaster predates on Mytilus mussels and makes space for many other species to colonise. The top predator Pistaster is a keystone species.
Kelp (brown algae) forest
Sea urchin (Echinus)
Sea otter (Enhydra)
Fisherig
__+_
_
Community
Global species pool
Regional species pools
Local species pools
Isolation filter
Abiotic filters
Abiotic filters Abiotic
filters
Abiotic and isolation filters at different spatial scales determine local species composition
Members of single communities pass these filters.
The distribution of species abundances
Relative abundances in a sequence of plant succession (Bazzaz 1975)
In natural comunities species abundances often differ by factors of more than 1000.That means that the most abundant species are 1000 times more abundant than the
rare species
Rank – abundance plot
Power function SAD Log-series SAD
Log-normal SAD
Log
abun
danc
e
Log
abun
danc
e
Log
abun
danc
e
Three types of relative abundance distributions (SAD)
𝑁=𝑒−𝑎×𝑛𝑜𝑟𝑚 (0,1)
𝑁=𝑁 0𝑖−𝑎
Species rank order i Species rank order i
Species rank order i
𝑃 (𝑁 )=𝛼 𝑋𝑛
𝑛P(N) is the probabiity that a species has exctly N individuals
Frank W. Preston (1896-1989)
Robert May of Oxford(1938-)
Ronald A. Fisher (1890-1962)Heavy tail
Power function SADLo
g ab
unda
nce
𝑁=𝑁 0𝑖−𝑎
Species rank order i
Parasitic Hymenoptera in a beech forest
Heavy tail
Power function SADs • have a high number of rare species (heavy
tail)• are input (colonization) driven
have a high degree of species turnover• often characterize species assemblages but not
true communitieshave a small number of very abundant species
• lack a larger number of intermediate abundant species
Examples• Incomplete samples• Arthropod assemblages• Disturbed habitats
Log-series SADLo
g ab
unda
nce
Species rank order i
Northern German Grassland spiders (Finch 2001)
The log series is a sample distribution. It describes the expected abundance of species in a sample from a large community. It applies to assemblages.
For fully censused assemblages it occurs most often• at early stages of succession• in disturbed habitats• in heterogeneous assemblages
𝑃 (𝑁 )=𝛼 𝑋𝑛
𝑛
Examples• Incomplete samples• Heterogeneous assemblages• Large arthropod samples
Log-normal SAD Lo
g ab
unda
nce
𝑁=𝑒−𝑎×𝑛𝑜𝑟𝑚 (0,1)
Species rank order i
Beetles in a Norwegian spruce forest (Ottesen 1996)
Lognormal SADs are derived from the central limit theorem of statistics that predict normal distributions
veil line Lognormal distributions occur most often in• closed and stable communities• undisturbed habitats• K- species dominated communities• Communities influenced by a large number
of divergent environmental factors.
High number of species with intermediate
abundance
Breeding birds of Ohio (Hicks 1935)
Often the distribution is not symmetrical having an excess of rare species.
𝑆=𝑆0𝑒−𝑎𝑅2
Diversity and evennness
A measure of diversity is the number of species
Abun
danc
e
Species
Abun
danc
e
Species
𝐻=1
∑1
𝑆
𝑝𝑖
Simpson index of diversity
𝐻=−∑1
𝑆
𝑝𝑖 ln ¿¿
Shannon index of diversity
𝑆=𝐻𝑙𝑛 (1+𝑁𝐻 )
Log-series index of diversity
Evenness
𝐸=𝐻𝑙𝑛𝑆
Diversity indices are measures of encounter probability
High evenness
Lower evenness
Alpha, beta and gamma diversity
Alpha diversity refers to the local number of speciesBeta diversity refers to the change in species composition among local habitatsGamma diversity refers to the regional species pool
Area
Spec
ies r
ichn
ess
a
g
b
Multiplicative partitioning of diversity
Additive partitioning of diversity
𝑦=𝛼 𝐴𝛽
Beta diversity is a measure of regional habitat diversity
Species interactions or neutrality
Stephen P. Hubbell (1942-
Motoo Kimura (1924-1994)
Neutral models lack any specific biological interaction like competition, mutualism, regulation, species specific survival.
Individuals are grouped to evolutionary lineages
Species are ecologically equivalent
0 0 0 0 0 0iJ J iJ bJ eJ dJ J Zero sum multinomial
BirthDeath
Pool of individuals
Random migration
Neutral models are individual based! Ecological drift
J is the total number of individuals
Neutral models provide ecological expectations without species interaction
Mutations
1
10
100
1000
10000
0 5 10 15 20 25 30Rank order
Abun
danc
e
Core species
0.1
1
10
100
0 5 10 15 20 25 30Rank order
Abun
danc
e
Satellite species
Neutral models make explicit predictions about
Abundance rank order relationships
Diversity and evenness
Ground beetles on lake islands in Lake Mamry (Ulrich and Zalewski 2007)
Leistus rufomarginatusPhotos by Roy Anderson
Neutral models make explicit predictions about
Regional diversity patterns
0
5
10
15
20
25
30
35
1 2 4 8 15Sites occupied
Spec
ies
Ground beetles on lake islands in Lake Mamry (Ulrich and Zalewski 2007)
Dyschirius globosus
Core and satellite species
Observed Predicted
Observed
Predicted
Ecological gradients and the classification of communitiesSpecies 1pog 2pog 3pog dab ful gil guc hel kor lip mil sos swiPterostichus melanarius 0 36 13 17 187 345 60 169 1199 704 394 428 13Pterostichus oblongopunctatus 0 2 7 135 83 188 11 8 1019 180 4 141 1Pterostichus niger 0 0 3 0 191 167 135 0 137 0 0 530 3Oxypselaphus obscurus 1 0 27 96 27 166 80 0 96 7 48 278 0Harpalus 4-punctatus 0 41 17 9 29 77 0 67 555 69 0 9 0Carabus granulatus 0 11 52 11 12 110 25 11 154 113 0 59 1Patrobus atrorufus 0 6 22 81 11 348 9 0 11 37 0 35 2Pterostichus antracinus 11 1 0 0 0 21 1 11 2 2 274 0 0Platynusas similis 0 7 25 4 48 39 2 9 76 117 0 9 0Pterostichus nigrita 30 2 2 5 1 58 1 0 0 2 39 18 0Carabus hortensis 0 0 0 0 75 52 109 0 0 0 0 0 0Pterostichus strennus 0 5 3 47 13 30 5 6 28 24 22 14 4
Ground beetles from Mazuran lake lands
SpeciesPterostichusmelanariusPterostichusoblongopunctatus(Fabricius)Pterostichusniger(Schaller)Oxypselaphusobscurus(Herbst)Harpalus4-punctatusDejeanCarabusgranulatusPatrobusatrorufus(Stroem)PterostichusantracinusPlatynusassimilis(Paykull)Pterostichusnigrita(Paykull)CarabushortensisLinnaeusPterostichusstrennus(Panzer)Pterostichusmelanarius0 787.7 1363 1393 1122 1359 1494 1515 1442 1541 1550 1518Pterostichusoblongopunctatus(Fabricius)787.7 0 1004 955.5 530.5 887.8 1040 1101 975.5 1062 1066 1030Pterostichusniger(Schaller)1363 1004 0 327.5 714.1 533.9 591.8 671 586.5 591 571.9 590.6Oxypselaphusobscurus(Herbst)1393 955.5 327.5 0 563.3 281.7 328.9 418.8 344.1 324.4 339 320.4Harpalus4-punctatusDejean1122 530.5 714.1 563.3 0 415.3 618.4 628.2 488 567.8 578 538Carabusgranulatus1359 887.8 533.9 281.7 415.3 0 299.4 354.5 127.5 215.1 239.6 192Patrobusatrorufus(Stroem)1494 1040 591.8 328.9 618.4 299.4 0 438.2 338 307.4 333.9 322.6Pterostichusantracinus1515 1101 671 418.8 628.2 354.5 438.2 0 311.9 239.7 305.9 259.9Platynusassimilis(Paykull)1442 975.5 586.5 344.1 488 127.5 338 311.9 0 157.2 180.7 123Pterostichusnigrita(Paykull)1541 1062 591 324.4 567.8 215.1 307.4 239.7 157.2 0 141.3 72.41CarabushortensisLinnaeus1550 1066 571.9 339 578 239.6 333.9 305.9 180.7 141.3 0 139.6Pterostichusstrennus(Panzer)1518 1030 590.6 320.4 538 192 322.6 259.9 123 72.41 139.6 0
Distance matrix
EV 1 EV 20.648 0.4960.368 0.361-0.059 0.298-0.179 0.2400.036 0.262-0.207 0.218-0.202 0.262-0.218 0.267-0.240 0.228-0.276 0.237-0.264 0.244-0.270 0.232
The first two eigenvectors
Principal component
analysis
Principal component analysis
PCA serves to identify ecological communities
Communities as ecological indicators
Ecological indicators are used to provide information about the state and the functioning of ecological systems.
Indicators might be single species , sets of species or whole communities.
Often used indicators
Anthropogenic disturbance Indicator
Acid rain MossesEutrophication Aquatic macrophytesInvasive species BirdsSedimentation ShrubsLogging Bark beetlesHeavy metals ProtozoaUrbanization Birds, CarabidsAir pollution PlantsAir quality Lichen