community ecology link to course web page. any set of organisms currently living near each other and...
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Community Ecology
Link to course web page
“any set of organisms currently living near each other and about which it is interesting to talk”
Painting by D. Kaspari for M. Kaspari (2008) – anniversary reflection on MacArthur (1958)
Robert H. MacArthur’s definition of Community Ecology
Historic landmarks
Community Ecology
Photo from Wikipedia
Charles Darwin (1809 - 1882)
Ernst Haeckel (1834 - 1919) coined “oekologie” for the study of the multifaceted “struggle for existence” envisioned by Darwin
Certainly not the first “ecologist,” but clearly recognized the importance of organisms’ interactions (intraspecific, interspecific & with their abiotic environments) for evolution by natural selection
Historic landmarks
Community Ecology
Photo from Wikipedia
Charles Darwin (1809 - 1882)
Recognized the importance of biotic interactions:
“Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain
flowers in that district!” (Darwin 1859)
Historic landmarks
Community Ecology
Photo from Wikipedia
Charles Darwin (1809 - 1882)
Recognized the importance of abiotic processes, e.g., abiotic disturbance:
“If turf which has long been mown… be let to grow, the most vigorous plants gradually kill
the less vigorous, though fully grown plants; thus out of 20 species growing on a little plot of mown turf (3 feet by 4 feet) nine species perished from the other species being
allowed to grow up freely…” (Darwin 1859)
Historic landmark
Community Ecology
Photo from UCSB
Joseph H. Connell (b. 1923)
Patterns – any observable properties of the natural world, often expressed as variable quantities or distributions (since variation characterizes
every level of biological organization)
Processes – the causal mechanismsthat give rise to the patterns
See also Watt (1947) Pattern and process in the plant community – J. Ecology
Community EcologyPatterns & Processes
Physiological constraints Biogeographical events
Habitat selection Dispersal ability
Competition
SPECIESCOMPOSITION OF THE
LOCAL COMMUNITY
Predation Mutualisms
REGIONALSPECIES
POOL
Evolutionary processes
Processes that determine local community composition (most of which produce community
structure that wouldn’t be predicted by null models)
Redrawn from Morin (1999, pg. 27)
Physiological constraints Biogeographical events
Habitat selection Dispersal ability
Competition
SPECIESCOMPOSITION OF THE
LOCAL COMMUNITY
Predation Mutualisms
REGIONALSPECIES
POOL
Evolutionary processes
Community A Community B
What relative contributions do the various processes make (and have made) towards maintaining (and originally creating) differences
between communities A and B?
Physiological constraints Biogeographical events
Habitat selection Dispersal ability
Competition
SPECIESCOMPOSITION OF THE
LOCAL COMMUNITY
Predation Mutualisms
REGIONALSPECIES
POOL
Evolutionary processes
Processes that determine local community composition (most of which produce community
structure that wouldn’t be predicted by null models)
Redrawn from Morin (1999, pg. 27)
Processes
Drift
Migration
Selection Abiotic environment Biotic interactions (e.g., competition, predation, etc.)
Speciation
Primary patterns(across space & time)
Species diversity
Species composition (identity & traits)
Species abundances
Emergent patterns
Productivity
Stability
Food-web connectance
Etc.
Redrawn from Vellend & Orrock (in press)
Parallels between Population Genetics & Community Ecology
These affect biological
variants, i.e., alleles or species
Local community
Regional community
Global communityDrift
SelectionSpeciation
DriftSelection
Speciation
DriftSelection
Speciation
MigrationMigration
MigrationMigration
Redrawn from Vellend & Orrock (in press)
Parallels between Community Ecology & Population Genetics
Local community A
Regional community
Global communityDrift
SelectionSpeciation
DriftSelection
Speciation
DriftSelection
Speciation
MigrationMigrationLocal
community B
DriftSelectionSpeciation
Redrawn from Vellend & Orrock (in press)
Parallels between Community Ecology & Population Genetics
MigrationMigration
Local community A
Global community
Local community B
Parallels between Community Ecology & Evolutionary Theory
Roughgarden (2009)
Local interactions Local interactions
In a parallel fashion the “formational theory of communnity ecology” could be: “local interactions act upon the species arriving at the community’s boundary to produce a diversity
of communities”
“the central narrative of evolutionary theory is that variation originates from random mutation and
then natural selection in a local setting acts upon this variation to produce organic diversity”
Supply-sideecology
Supply-sideecology
A B
Competition
-
-
Influence of species A
Infl
ue
nce
of
Sp
eci
es
B
+ (positive)0 (neutral/null)- (negative)
A B
Amensalism
0
-A B
Antagonism(Predation/Parasitism)
+
-
A B
Commensalism
+
0A B
Neutralism(No interaction)
0
0
A B
Commensalism
0
+A B
Mutualism
+
+
A B
Amensalism
-
0
A B
Antagonism(Predation/Parasitism)
-
+
-
0
+
Pair-wise species interactions(owing to acquisition or assimilation of resources, etc.)
Redrawn from Abrahamson (1989); Morin (1999, pg. 21)
To separate Ecology and Evolution into separate disciplines is somewhat artificial
Nothing in biology makes sense except in the light of evolution (T. Dobzhansky 1973)
All organisms interact with other organisms, both conspecific and heterospecific, and their environments; i.e., the
evolutionary play takes place within an ecological theater(G. E. Hutchinson 1965)
Ecologists and evolutionary biologists must recognize and embrace the complexity of natural ecosystems to understand them, and their components, much as Zen masters recognize
and embrace the interconnectedness of the universe(D. P. Barash 1973)
Just as is completely separating Community Ecologyfrom other related sub-disciplines
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