Lecture 2-3 Flashcards
(23 cards)
What is community and population ecology
Interactions of communities and populations with the environment.
Community: a group of species that occur in the same place and time
Issue?
- limits on space and time are arbitrary
Clemens vs Gleason
Clemens: coherent unit/super organism concept
Clements considered the different species in a community as being tightly integrated and interdependent
Can only occur in highly discreet resources (^speciation) and sharp ecological boundaries (isolated)
-There is predictable and directional evolution of a community due to /modification in the physical environment, cumulating in stable climax community
- Primary succession (start from 0) vs secondary succession (disturbance)
ex. islands
Gleason’s individualistic concept of communities
- species distribution based on environmental factors and random collection of species together
What is the seminal quote in ecology?
In ecology, we…
…are explores (ask questions)…adapt (experiment in unpredictable field)… Imaginative (why /what)… Safe things will go wrong, never safe results
What is Gausin’s principal of competitive exclusion?
Species competing for a single resource can not coexist
They must each occupy different niches
Populations are regulated by density dependent factors (decrees in resource availability) or density independent factors (ex. volcano)
BD
CPE
Niche:
What’s the fundamental niche, ecological role and niche overlap?
The fundamental niche is the environment in which an organism is capable of living in the absence of interactions
Ecological role: role a species plays in a community
Niche overlap=competition=realized niche= environment actually occupied in presence of competing species
Typically, the realized niche is smaller to the fundamental niche except in cases where there is strong positive interspecific interactions
Hutchinson and the niche
Quantified organism’s niche, noting biotic and abiotic factors as axis in dimensional hyperspace
there are infinant dimensions
we typicaly consider 3
How dissimilar must animals be in order to coexist?
(Competitive exclusion principle)
Animals of the same glide may coexist depending on size of their food
We use the Hutchinsonian ratios to determine this
multiply length by 0.3
and mass by 2
Draw the graph explaining the concept of limiting similarity
What are the issues with this concept?
d/w=1 this is the minimum niche separation for co-existence
d= distance between means
w= standard deviation
k= resource continuum
y=resource quantity
x=resource size
overlap between curves= niche overlap (interspecific competition)
Issues:
- not all species are normally distributed
- Other factors influence besides just resources and body size
Diversity is high when predators feed on….
Dominant species (largest quantity)
How does community ecology relate processes to patterns
Selection
Drift
Dispersal
Speciation
Latitudinal diversity gradient and the 5 things that effect it
Species richness increase from the poles to the equator.
effected by scale (regional/local), sample grain (large /small) realm (marine terrestrial freshwater) body size (large/small) and trophic level (high/low)
What are the four main hypothesis for the Latitudinal; biodiversity gradient
- Null hypothesis (mid domain effect)
- Ecological hypothesis (energy availability)
- Historical explanations (time area hypothesis +tropical niche conservation)
- Evolutionary hypothesis (diversity ratios)
The Null hypothesis
What if the latitudinal diversity gradient was random?
-Based random dynamic species ranges distributed across the globe
- Mid-domain effect has fixed boundaries at the poles and random
- By itself it’s an unlikely explanation
Testing the mid-domain effect
Use different patterns of die to test
Added biographic regions and actual evapotranspiration (energy)
- mid to main effect on it’s own cant explain the LDG and energy is a key factor driving the relationship
The pencil box and the null model
Pencil box represents defining boundaries on earth
each pencil= diff species
size=rang-held constant
If you shake the box, where species occur is randomized
Relative to the poles, there will always be more species in the middle
What is the latitudinal diversity gradient (LDG)?
What does the null model suggest about LDG?
What is the mid-domain effect (MDE)?
What are limitations of the null model?
LDG is the pattern of increasing species richness toward the equator.
The null model suggests LDG may result from random geographic range placement, not biological factors.
MDE states that randomly placed species ranges will overlap more near the center (equator), creating a diversity peak.
It ignores biological processes like speciation rates, extinction rates, and ecological interactions.
Explain the Ecological Hypothesis
Pros cons….
ENERGY AVAILABILITY
- there is more energy and water at the equator per unit area
- More energy— more individuals— variation—more species
- tested with trees and birds consistent with the theory, BUT observered increase in # of species per individual greater than predicted
- The species individual curve: reflects the smallest minimum # of individuals needed for a min pop
(try to draw)
Historical approach
Time area hypothesis + tropical niche conservation
- based off idea that tropical environments are older and historically more widespread
Being older allows more time for desertification
-fewer disturbances took place in tropics
Tropical niche conservation: transition from ancestorial species from tropical to temperate is hard because of phylogenetic hurdles
Evolutionary hypothesis
Diversity ratios
- Mix between ecological and historical approach
-Cradle (historical):preservation of new taxa in mild +stable environments
-Museum (historical): preservation of existing diversity, genetic similarities in smaller pops
- Consistent with fossil records
This hypothesis requires other factors
- Initial diversity (in small pop)
- Higher mutation ratios (TUV)
- Shorter generation times (higher temperature )
- Stronger biotic interaction higher co-evolution
Marine LDG
More complex because:
- less contained
3rd dimension of depth
- temperature varies differently
Temperature varies less dramatically at the poles
And more at the equator
(Opposite of terrestrial)
Biodiversity at different spacial ratios
a-diversity= # of species at a local site
B-diversity= difference between two sites species composition within a region
Gamma diversity=total number of species in a landscape or region. It’s a way to describe the overall biodiversity of an area.
5 spacial designations
Biogeographical region/realm
- Fixed by major geographic/climate realms (shared evolutionary history)
- limit dispersal over evolutionary time (dispersal does not affect diversity measurements)
-Usually continuous area
ex. continent
Province: same but smaller
Biome/ecoregion: defined by climate, and it’s association with biotic factors
Marine defined by : salinity, temp, movement, light, substrate composition
ex. tundra
Region: (many km2) with many habitats and communities
Level of speciation and extinction
ex. Toronto area red side days
Local:
- < 1m- km2
- defined by likelihood of species interaction
ex. Tecumseh
