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.

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