Lecture 23 Community Assembly Flashcards
Community Structure
- Community structure is defined by species composition: species present
and their relative abundances - Community structure reflects ecological niches: A species must first be
able to survive to be part of a community!
slide 3-6
Interspecific Interactions
slide 7
Species Interactions: Competition
Species compete for a limited
resource
* Survival and reproduction of both
species decreases
* Can lead to competitive exclusion
and resource partitioning
slide 8-10
Species Interactions: Exploitation
One species benefits by feeding on another species
* Predation: one species kills and eats the other
* Herbivory: one species eats a primary producer
* Parasitism: one species derives nourishment or other benefit
from another
Predation & Herbivory
slide 12-13
Parasites
slide 14-16
Species Interactions: Facilitation
One species benefits while the other
either benefits as well or is unharmed
* Mutualism: everyone benefits (and
bears the costs)!
* Commensalism: One species benefits
and the other is unharmed
slide 17-18
Community Stability
Why don’t ecosystems collapse
when species are lost?!
- Some species are redundant (diffuse effects)
- Some species impact the function of the community more than
others (influential species) - Sometimes they do collapse (trophic cascades)
Community Stability: Diffuse Effects
Why don’t ecosystems collapse
when species are lost?!
Some species are redundant
Community Stability: Diffuse Effects
slide 21-22
Community Stability: Influential Species
Why don’t ecosystems collapse
when species are lost?!
Some species impact the function of
the community more than others:
* Foundation species
* Keystone species
* Ecosystem engineers
Foundation Species
- Foundation species have strong
effects because of their large size
or high abundance - Provide habitat or food
- May be competitively dominant
(superior in exploiting key
resources of space, water,
nutrients, light) - Impact is apparent when
removed
slide 24-25
Ecosystem Engineers
- Ecosystem Engineers create or dramatically alter the environment
- Effects can be positive or negative on other species
- Foundation species can be considered ecosystem engineers
slide 26
Keystone Species
- Keystone species exert a strong control on community structure because of
their critical ecological role - Effect is disproportionate to their abundance
- Removal initiates substantial change in community structure
- Function by creating habitat or through species interactions
slide 27-33
Community Assembly
slide 34
