Geography Resources Phylogeny Community Redrawn from Fauth et al 1996 Community collection of species that occur at the same place amp time circumscribed by natural eg serpentine soil arbitrary or artificial ID: 932541
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Slide1
Community Ecology
(Toti-omics)
Slide2Geography
Resources
Phylogeny
Community
Redrawn from Fauth
et al
. (1996)
Community
– collection of species that occur at the same place & time, circumscribed by natural (
e.g
., serpentine soil), arbitrary, or artificial (
e.g
.,
1-m
2
quadrat) boundaries
Many prefer a more
restrictive definition
in which species must interact to be included,
e.g.
, Whittaker (1975)
Slide3Geography
Resources
Phylogeny
Taxon
Taxon
– phylogenetically related group of species; a
clade
or
phylad
E.g.
, Mammalian Order Rodentia
Community
Redrawn from Fauth
et al
. (1996)
Slide4Geography
Resources
Phylogeny
Community
Guild
Guild
– a group of species “without regard for taxonomic position” that “exploit the same class of environmental resources in a similar way” (Root 1967)
E.g.
, granivores
Taxon
Redrawn from Fauth
et al
. (1996)
Slide5Geography
Resources
Phylogeny
Community
Guild
Local
guild
Local guild
– a group of species that share a common resource and occur in the same community
(Root 1967)
E.g.
, Sonoran Desert granivores
Taxon
Redrawn from Fauth
et al
. (1996)
Slide6Geography
Resources
Phylogeny
Community
Guild
Local
guild
Assemblage
Assemblage
– a group of phylogenetically related species within a community
Taxon
Redrawn from Fauth
et al
. (1996)
Slide7Geography
Resources
Phylogeny
Community
Guild
Local
guild
Assemblage
Assemblage
– a group of phylogenetically related species within a community
a.k.a. “
Taxocene
” (Hutchinson 1967)
E.g.
, Sonoran Desert rodents
Taxon
Redrawn from Fauth
et al
. (1996)
Slide8Geography
Resources
Phylogeny
Community
Guild
Taxon
Ensemble
Local
guild
Assemblage
Ensemble
– a phylogenetically bounded group of species that use a similar set of resources within a community
E.g.
, Sonoran Desert granivorous rodents
Redrawn from Fauth
et al
. (1996)
Slide9Geography
Resources
Phylogeny
Community
Guild
Taxon
Local
guild
Assemblage
E.g
.,
granivorous rodents,
pond-breeding salamanders…
Ensemble
In this course any collection of two or
more species is
“fair game” for close
scrutiny
Redrawn from Fauth
et al
. (1996)
Slide10“
Any set of organisms currently living near each other and
about which it is interesting to talk
” (MacArthur 1971)
Painting by D. Kaspari for M. Kaspari (2008) – anniversary reflection on MacArthur (1958)
Robert H. MacArthur’s definition of Community
Slide11Some historic landmarks
Community Ecology
has matured from purely descriptive studies (
i.e.
, description & analysis of
patterns
) to mechanistic studies (
i.e.
, investigations into
processes) that aim to improve our explanatory & predictive abilities
In any case, the tradition of good Natural History is not ignored by the best modern practitioners
Community Ecology
“
Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders.” (H. D. Thoreau ~1860)
Slide12Some historic landmarks
Community Ecology
Photo of
Darwin
from WikiMedia Commons
Charles Darwin (1809 - 1882)
Ernst Haeckel (1834 - 1919)
coined “
oekologie
”
for the study of Darwin’s multifaceted “struggle for existence”
Not the first “ecologist,” but clearly recognized the importance of organisms’
interactions
(intraspecific, interspecific & with their abiotic environments) for evolution by natural selection
Slide13Some historic landmarks
Community Ecology
Photo of
Darwin
from WikiMedia Commons
Charles Darwin (1809 - 1882)
On
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)
Slide14Some historic landmarks
Community Ecology
Photo of
Darwin
from WikiMedia Commons
Charles Darwin (1809 - 1882)
On
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)
Slide15Some historic landmarks
Community Ecology
Photo of
Richards
from WikiMedia Commons; for further details see Damschen
et al
. (2005)
Ellen Swallow Richards (1842 - 1911)
Chemist who probably “created and taught the first ecology curriculum” in the U.S. and may have introduced the term “
ecology
” into the English language (from Ernst Haeckel’s “
oekologie
”)
Slide16Some historic landmarks
Photo of
Forbes
from http://home.grics.net...
Stephen Forbes (1844 - 1930)
Community Ecology
One of the earliest ecologists to examine multiple, cross-trophic level interactions simultaneously within an explicitly evolutionary framework
Wondered how in spite of a constant “struggle for existence” some
balance
is nevertheless maintained in
ecosystems
(see:
The lake as a microcosm,
1887)
Slide17Some historic landmarks
Community Ecology
Photo of
Cowles
from http://oz.plymouth.edu...
Photo of
Lake Michigan sand dune
from http://ebeltz.net...
Henry Cowles (1869 - 1939)
A pioneer of “
dynamic ecology
,” especially on the sand dunes of Lake Michigan
Slide18Some historic landmarks
Community Ecology
In the grand traditions of
Alexander von Humboldt (1769 - 1859; the “father of biogeography”)
&
Alfred Russel Wallace (1823 - 1913)
…
Clinton Hart Merriam (1855 - 1942)
also noticed that geographic changes in physical conditions often coincide with changes in biotaMerriam devised Empirical Life Zones (similar biotic changes with increased elevation or latitude)
Slide19Some historic landmarks
Community Ecology
Leslie Holdridge (1907 - 1999)
– devised
Theoretical Life Zones
(1947)
Image from WikiMedia Commons
Slide20Some historic landmarks
Community Ecology
Clements
vs.
Gleason
(1920s & 1930s)
Frederic Clements (1874 - 1945)
– thought succession always reached a predictable
climax community
; viewed communities metaphorically as “superorganisms”
Henry Gleason (1882 - 1975)
– proposed the “
individualistic concept
” of communities; discrete populations whose patterns of distribution and abundance give rise to communities as epiphenomena
Slide21Photo of
Whittaker
from WikiMedia Commons; figures from http://ecology.botany.ufl.edu...
Some historic landmarks
Community Ecology
Robert H. Whittaker (1869 - 1939)
His
gradient analyses
helped end the
Clements-Gleason debate
Slide22Some historic landmarks
Community Ecology
We continue to need good descriptions of patterns, often supported by sound, quantitative techniques
See: The Ordination Web Page (
http://ordination.okstate.edu
)
E.g.,
the Ecological Society of America, The Nature Conservancy, the U.S. Geological Survey, the U.S. National Park Service & others collaborate to continue to refine the
National Vegetation Classification Standard (NVCS)
E.g.
,
Bray & Curtis (1957)
introduced
ordination methods
to define plant communities in Wisconsin
Slide23Photo of
Davis
from U. Minnesota; photo of
pollen
from http://www.gl.rhbnc.ac.uk...
Some historic landmarks
Community Ecology
Margaret Davis (b. 1931)
Her paleo-ecological perspective has
helped increase awareness of
historical contingencies
Slide24Photo of
Connell
from UCSB
Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Heralded as milestones in ecology, his studies demonstrated the utility of
field experiments
for answering ecological questions; empirically assessed
multiple hypotheses
for intertidal zonation
The concept of
equifinality
was formalized by
Ludwig von Bertalanffy (1968; founder of General Systems Theory) – multiple hypotheses or mechanisms can equally explain or generate the same pattern
Slide25Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Observations:
Balanus balanoides
– Larger barnacle, generally found lower in the intertidal
Chthamalus stellatus
– Smaller barnacle, generally found higher in the intertidal
Photo of
Connell
from UCSB
Slide26Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Photo of
Connell
from UCSB
Slide27Some historic landmarks
Why might these patterns exist?
Community Ecology
Joseph H. Connell (b. 1923)
Observations of Pattern:
Balanus balanoides
– Larger barnacle, generally found lower in the intertidal
Chthamalus stellatus
– Smaller barnacle, generally found higher in the intertidal
Photo of
Connell
from UCSB
Slide28Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Mechanistic Hypotheses:
Differential
physiological tolerances to desiccation and submersion
Interspecific competition
Predation (
e.g., Thais lapillus is a predator of Balanus balanoides)
Photo of Connell from UCSB
Slide29Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Testable Predictions:
If physiology determines distribution patterns,
to remove potential competitors or predators should have no effect
If competition/predation determines distribution
patterns, to remove competitors/predators
should result in altered patterns of distribution
Photo of
Connell
from UCSB
Slide30Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Exclusion experiments, results & conclusions:
The absence of competitors & predators produced no change in upper level of distributions
For
Chthamalus
, removing
Balanus
increased downslope survivorship & distribution
For
Balanus, removing Thais increased downslope survivorship & distribution
Photo of Connell from UCSB
Slide31Some historic landmarks
Community Ecology
Joseph H. Connell (b. 1923)
Photo of
Connell
from UCSB; figure from Connell (1961; one of Connell’s 5 Science Citation Classics)
Slide32Some historic landmarks
Photo of
MacArthur
from Wikipedia
Community Ecology
Robert H. MacArthur (1930 - 1972)
More than most of his predecessors, MacArthur demonstrated the utility of
simplifying assumptions
combined with
mathematical rigor
for exploring ecological problems
Criticisms: oversimplification; over-emphasized competition & equilibria
Slide33Some historic landmarks
Community Ecology
G. Evelyn Hutchinson (1903 - 1991)
Photo of
Hutchinson
from Yale Peabody Archives
Conceived of
fundamental
vs.
realized
niche
spaces
or hyper-volumes
“Ecologists use the metaphor of the ‘ecological niche’ to express the idea that plant and animal species play certain roles in the ecological community” (Kingsland 2005, pg. 1)
Slide34Some historic landmarks
Figure from Gotelli & Graves (1996, pg. x)
Community Ecology
G. Evelyn Hutchinson
The idea & disagreement over how to
test it helped motivate the development
of
null models in ecology
E.g.
, Hutchinsonian ratios
A ratio of ~ 1.3 in size
occurs between pairs of
coexisting species,
possibly owing to inter- specific competition
Slide35Community Ecology
Some historic landmarks
“
Null hypotheses [models]
entertain the possibility that nothing has happened…
” (Strong 1980)
“
A
null model
is a pattern-generating model that is based on
randomization of ecological data or random sampling from a known or imagined distribution. The null model is designed with respect to some ecological or evolutionary process of interest. Certain elements of the data are held constant, and others are allowed to vary stochastically to create new assemblage patterns. The randomization is designed to produce a pattern that would be expected in the absence of a particular ecological mechanism…” (Gotelli & Graves 1996)
Slide36Some historic landmarks
Community Ecology
Photo of
Hubbell
from UCLA
Stephen P. Hubbell (b. 1942)
Neutral theory
…
asks how well community-level patterns conform to predictions under the simplifying assumption that all individuals are equal (in terms of probability of recruiting, dying, and replacing themselves through reproduction)
“
When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this!
”
(C. Darwin 1859)
Slide37Patterns
– 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
mechanisms
that give rise to the patterns
See also Watt (1947) “Pattern and process in the plant community” –
J. Ecology
Community Ecology
Patterns & Processes
Slide38Community Assembly / Coalescence
From: J. N. Thompson
et al
. 2001. Frontiers of Ecology.
BioScience
51:15-24.
“We use the term
community coalescence
to refer to the development of complex ecological communities from a regional species pool. This coalescence depends on interactions among species availability,
physical environment, evolutionary history, and temporal
sequence of assembly.”
Slide39Processes 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)
Slide40Community 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?
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)
Slide41Processes that determine local community composition
(most of which produce community structure that
wouldn’t be predicted by null models)
From HilleRisLambers
et al
. (2012, pg. 228)
Slide42Processes
Drift
Migration
Selection
Abiotic environment
Biotic interactions
(
e.g.
, competition, predation,
etc
.)
Speciation
… and extinction (owing to drift & selection)
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 (2010)
These affect biological variants,
i.e.
, alleles or species
Parallels between Community Ecology & Population Genetics
Slide43Local
community
Regional community
Global community
Drift
Selection
Speciation
Drift
Selection
Speciation
Drift
Selection
Speciation
Migration
Migration
Migration
Migration
Redrawn from Vellend & Orrock (2010)
Parallels between Community Ecology & Population Genetics
Slide44Local
community A
Regional community
Global community
Drift
Selection
Speciation
Drift
Selection
Speciation
Drift
Selection
Speciation
Migration
Migration
Local
community B
Drift
Selection
Speciation
Redrawn from Vellend & Orrock (2010)
Parallels between Community Ecology & Population Genetics
Migration
Migration
Slide45Redrawn from Vellend (2010)
Parallels between Community Ecology & Population Genetics
“
species are added to
communities via speciation and dispersal,
and the relative abundances of these species are then shaped by drift and selection, as well as ongoing dispersal, to drive community dynamics
”
Local
community A
Regional community
Local
community B
Slide46Local
community A
Global community
Local
community B
Parallels between Community Ecology & Evolutionary Theory
From 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-side
ecology
Supply-side
ecology
Slide47A
B
Competition
-
-
Influence of species A
Influence of Species B
+ (positive)
0 (neutral/null)
- (negative)
A
B
Amensalism
0
-
A
B
Antagonism /
Contramensalism
(Predation / Parasitism)
+
-
A
B
Commensalism
+
0
A
B
Neutralism
(No interaction)
0
0
A
B
Commensalism
0
+
A
B
Mutualism
+
+
A
B
Amensalism
-
0
A
B
Antagonism /
Contramensalism
(Predation / Parasitism)
-
+
-
0
+
Pair-wise species interactions
(owing to acquisition or assimilation of resources,
etc
.)
Redrawn from Abrahamson (1989); Morin (1999, pg. 21)
Slide48Interactions are often
asymmetric
, even when the sign of the interaction is the same in both directions (
e.g., obligate
for one organism, but
facultative
for the other)
Pair-wise species interactions
Species A
Species B
+
/
+
_ / +
+ / _
_ / _
Slide49In any case, the
laws of physics & chemistry
apply
(e.g., thermodynamics & stoichiometry)
Are there “laws” specific to Ecology,
and Community Ecology in particular?
Laws in Community Ecology
Slide50To separate
Ecology
and
Evolution
into separate
disciplines is somewhat artificial
Nothing in biology makes sense except in the light of evolution
(T. Dobzhansky [an architect of the Modern Synthesis] 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