Lecture 21: Community Structure Flashcards
Community is the sum of
coevolution and interactions of
- predator/prey
- competition
- mutualisms
Community
groups of interacting species that occur together at the same place and time
What is example of clear division between communities?
Waterline
Communities defined by
- Dominant species
- Physical characteristics of the environment
Ex. Oak hickory forest, hot springs community
Whole food web is a
community
Taxonomic affinity
Refers to the degree of similarity between organisms based on their classification within a specific taxonomic group
Communities of birds are grouped by
taxonomic affinity
Guild
group of species that use the same resources, even though taxonomically distant
Ex of Guild
Organisms (bat, bee, hummingbird) foraging for floral resources (nectar and pollen)
Functional group
species that function in similar ways, but aren’t necessarily related or use the same resources
Ex of functional group
Different phytoplankton (diatom, coccolithophores, dinoflagellate)
Diatom use lots of Si
Coccolithophores use lots of Ca
Dinoflagellates eat bacteria
But they all float around and photosynthesize
Species composition
species present in the community
Species diversity
measure of variation in species in the community
includes species richness and species evenness
Species richness
Number of species
Species evenness
Commonness or rareness of the species
Shannon Diversity index (H)
incorporates both number and evenness of species
Rank abundance curve
To look at whole community at once
Helpful for examining diversity data of real communities
Community interactions can be:
- direct/indirect: exploitative and interference
- trophic cascade: food web
- competitive networks
Competitive interactions among species include:
Competition intransitivity: competitive network
Competitive/linear hierarchy
Competitive intransitivity
rock/paper/scissors
competitive network
in real communities
hot topic in ecology because it’s so hard to explain species coexistence from other theories
data is not very convincing at the moment
Keystone species
species that affects the rest of the community disproportionately to the amount of energy that goes through it
Ex. Piaster
Foundation species
large or abundant species that have large community wide effects by providing habitat or food
Ex. Trees
Engineering species
Species that create an entire habitat
Ex. Beaver create beaver dam
Size and abundance and effect of normal species
Small size and abundance
Small effect of species
Ex. Birds
Size and abundance and effect of keystone species
Small size and abundance
Large effect of species
Ex. Beaver
Size and abundance and effect of foundation species
Large size and abundance
Large effect of species
Ex. Trees
What are the 2 community concepts on how communities assembled?
- Clements: Coevolved superorganisms
- Gleason: Sum of independent species distributions
Clements community concept
Communities assemble almost as superorganisms
Communities are group of species that worked together, with all of the species filling their particular niche to get to a stable end point
Gleason community concept
Species differential responses to environmental conditions matter
Each community is unique set of species dependent on particular environment of the place and time
How are communities actually assembled?
Mixture of both Clements and Gleasons ideas
Fundamental niche
Gleason
Variation in optima generate independent distributions
Realized Niche
Clements
Competition: more restricted, separating species
Facilitation: keeping species together
Ecology
study of interaction among species (clements) with their environment (gleason)
