change through time community ecology Flashcards
what are 3 biotic drivers of change in a community ?
- Inter-specific interactions (= selection)
- Demographic stochasticity (= drift)
- Invasive species ( = dispersal + selection)
what are 3 abiotic drivers of change in a community ?
- Global change: habitat loss & fragmentation, climatic change…
- Eutrophication, pollutants…
- Disturbance: floods, wildfires, treefall, pollutant release
what are the two main factors causing variation in a stationary community ?
intrinsic dynamics and extrinsic disturbances
What does “stationary” mean in the context of community structure in ecology?
It refers to a broadly constant community structure or other state variables (e.g., biomass) over time
How does a stationary community structure vary over time?
It likely varies around a long-term equilibrium
What are examples of extrinsic disturbances that can affect a stationary community?
Drought, flood, and wildfire
What is the ultimate endpoint of long-term directional ecological change often referred to as?
A “climax” community.
What natural process often initiates primary succession
Volcanic activity or other events creating bare, lifeless surfaces
What is the difference between primary and secondary succession?
Primary succession occurs on lifeless areas with no soil, while secondary succession occurs where soil is present but the community has been disturbed
What are the two types of ecological succession associated with long-term directional change?
Primary succession and secondary succession.
What patterns characterize long-term, directional ecological change?
Directional patterns of colonizations and extinctions.
What can trigger a dramatic shift between alternative stable states?
Small environmental changes.
What are “alternative stable states” in ecology?
They are different stable community structures that can exist under similar environmental conditions.
Why is it difficult to reverse a shift between alternative stable states?
It requires a disproportionately large change in the environment to drive the system back
What are the two alternative stable statesfor eutrophic shallow lakes?
Clear water: Dominated by macrophyte growth with zooplankton suppressing phytoplankton.
Turbid water: Dominated by abundant phytoplankton, with fish suppressing zooplankton due to reduced shelter and sediment resuspension.
In a clear-water state, what factors suppress phytoplankton growth?
Zooplankton and macrophyte growth.
What causes a shallow lake to shift to a turbid state?
Fish activity suppressing zooplankton, reduced shelter, and resuspension of sediment.
What evidence shows a shift in diet among surviving species after the collapse?
Stable isotope analysis
Which types of species survived the collapse of Australian megafauna?
Only adaptable species, such as the emu and wombat
What ecological changes accompanied the collapse of Australian megafauna?
Changes in vegetation and fire regimes
How many species of Australian megafauna were lost after human colonization?
60spp
What are two causes of ecological collapse
fisheries and desertification
What are the four properties used to detect changes in community response?
Abundance distributions
Evenness (dominance)
Richness
Composition
How can overall changes in community structure be quantified?
Using dissimilarity measures
