Community Ecology

Front 1

species richness

Back 1

- raw species count
- rare species do not have a big effect on community function
- doesn't allow for relative abundances

Front 2

Diversity index

Back 2

accounts for both richness and relative abundance

Front 3

Alpha Diversity

Back 3

diversity within a single community

Front 4

rarefaction curve

Back 4

curve showing change in species richness w/ sample size

- height = species richness (higher peak = more richness)

- slope = evenness
(greater slope = more evenness)

Front 5

relative abundance

Back 5

species evenness

Front 6

Beta Diversity

Back 6

differences between communities (Max beta diversity = no similarity)

- shows how unique the community is

Front 7

Why is there greater species diversity in the tropics (8 hypotheses)

Back 7

1. Productivity Theory
2. Spatial heterogeneity
3. Competition
4. Predation
5. Pollinators
6. Time
7. Area
8. Evolutionary speed

Front 8

Effects of diversity

Back 8

- important for
ecosystem function & services - ability of ecosystems to cycle nutrients, atmospheric gas, deal w/ disturbances, provide important resources

(1) Greater diversity yields greater productivity
- primary production = conservation of energy from non-biological sources (mostly sunlight) into biological growth

(2)Diverse communities are more resistant to:

a. foraging
b. drought
c. fire
d. floods
e. invasive species

Front 9

succession

Back 9

change in community structure following disturbance or creation of new habitat

Front 10

primary succession

Back 10

on absolutely bare substrate

Front 11

secondary succession

Back 11

colonization of partly cleared substrate

Front 12

pioneer species

Back 12

species making up 1st serial stage

Front 13

climax community

Back 13

traditional view that succession will eventually lead to a stable community of the most K-selected species

Front 14

3 Models of Succession

Back 14

(1) Facilitation - each species' replacement is facilitated by previous colonists

(2) Tolerance - pattern of succession in driven by competitive ability
- better competitors replace poorer competitors

(3) Inhibition - early invading species inhibit competitors from entering. Only disturbance will allow new successional stages.

- THEREFORE, inhibition STOPS succession

IN ALL 3, competition is important

Front 15

ecosystems

Back 15

biological communities & physical environment

Front 16

food webs & types (3)

Back 16

patterns of consumption showing how energy passes through the community (network of consumer relationships)

Types of food webs:
(1) connectedness of food web - only the presence/ absence of a trophic interaction

(2) energy web - connections are weighted by the strength of the interaction

(3) functional food web - only interactions that are most important to community structure

Front 17

food chain

Back 17

(multiple within food webs)

- show energy flow from primary producers through a series of consumers

- each successive link is a higher trophic level

Front 18

Food Web Patterns

Back 18

(1) Relatively few trophic levels, usually <5. Hypotheses:

a. Energy flow hypothesis - due to inefficient energy transfer between trophic levels

b. dynamic stability hypothesis - more complex food webs (w/ more trophic levels) cannot recover from disturbance-> don't persist

(2) More species = greater chain length

(3) connectance is is relatively constant regardless of species #

Front 19

Keystones

Back 19

species whose effect on the community are greater than their abundance of biomass

Front 20

dominant species

Back 20

large effect on community b/c they are very common (Ex: Maple trees & Beeches in forest, people)