Community Ecology
Geography
Resources
Community
Community – collection of
species that occur at the
same place & time,
circumscribed by natural
(e.g., serpentine soil),
arbitrary, or artificial (e.g.,
1-m2 quadrat) boundaries
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Geography
Resources
Community
Community – “Any set of
organisms currently living
near each other and
about which it is interesting to
talk” (MacArthur 1971)
Many prefer a more
restrictive definition
in which species must
interact to be included,
e.g., Whittaker (1975)
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Geography
Resources
Community
Taxon – phylogenetically
related group of species;
a clade
Taxon
E.g., Mammalian Order
Rodentia
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Geography
Resources
Guild
Community
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
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
Geography
Resources
(or Function)
Community
Functional
Group
Taxon
Functional Group – a group
of species that share similar
functional attributes (this was
not part of the original
scheme)
E.g., nitrogen-fixers
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Geography
Resources
Local
guild
Community
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
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
Geography
Resources
Local
guild
Community
Guild
Assemblage
Assemblage – a group of
phylogenetically related
species within a community
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Geography
Resources
Local
guild
Community
Guild
Assemblage
Assemblage – a group of
phylogenetically related
species within a community
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
E.g., Sonoran Desert
rodents
Geography
Resources
Local
guild
Community
Guild
Ensemble
Assemblage
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
Ensemble – a
phylogenetically bounded
group of species that use a
similar set of resources
within a community
E.g., Sonoran Desert
granivorous rodents
Geography
Resources
Local
guild
Community
Guild
Ensemble
Assemblage
Taxon
Phylogeny
Redrawn from Fauth et al. (1996) Am. Nat.
E.g.,
granivorous rodents,
pond-breeding
salamanders…
Community Assembly
“Community membership depends on arriving at a site, coping with the site’s
physical environment, and interacting with other species living there”
Evolutionary processes
Physiological constraints
Biogeographical events
REGIONAL
SPECIES
POOL
Habitat selection
Competition
Dispersal ability
Predation
Mutualisms
SPECIES
COMPOSITION OF THE
LOCAL COMMUNITY
Quote from Cain, Bowman & Hacker (2014), pg. 357; figure redrawn from Morin (1999, pg. 27)
Parallels Between Community Ecology & Pop. 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
Global community
drive community
Drift
dynamics”
Selection
Speciation
Dispersal
Dispersal
Regional community
Drift
Selection
Speciation
Dispersal
Redrawn from Vellend & Orrock (2010)
Local
community A
Drift
Selection
Speciation
Local
community B
Drift
Selection
Speciation
Dispersal
Food Webs & Interaction Webs
Cain, Bowman & Hacker (2014), Fig. 16.5
Food Webs & Interaction Webs
Cain, Bowman & Hacker (2014), Fig. 16.5
Multi-Species Interactions
Cain, Bowman & Hacker (2014), Fig. 16.13
Multi-Species Interactions
Cain, Bowman & Hacker (2014), Fig. 16.15
Species Richness & Diversity
Species Composition (the species present)
A has the same species as B
Species Richness
A=B
Species Evenness
A<B
Species Diversity
A<B
Cain, Bowman & Hacker (2014), Fig. 16.6
Species Diversity
Incorporates both Species Richness & Evenness
Cain, Bowman & Hacker (2014), Table 16.1
Species Diversity – Rank Abundance Curve
Cain, Bowman & Hacker (2014), Fig. 16.8
Species Diversity – Species Accumulation Curve
Cain, Bowman & Hacker (2014), Fig. 16.10
Relative Influence of Species
Dominant / Foundation Species
Single species that defines much
of the structure of a community
(Dayton 1972)
Photo from Wikimedia Commons
Relative Influence of Species
Ecosystem Engineers
Organism that changes the environment by transforming living or nonliving
materials from one physical state to another, via mechanical or other means
(Jones et al. 1994)
Photo of beaver dam on Tierra del Fuego from Wikimedia Commons
Relative Influence of Species
Keystone Species
E.g., Keystone predator – a predator (e.g., Pisaster seastar) whose activities
maintain species diversity at lower trophic levels by
disallowing competitive exclusion
(Paine 1966)
Photo from Wikimedia Commons
Relative Influence of Species
Redundant Species
Like the multiple rivets in an airplane
Photos of red-winged blackbird and yellow-headed blackbird from Wikimedia Commons
Neutral Theory
Steve Hubbell
What if all individuals have the same per capita influence?
Photo of S. P. Hubbell from UCLA